Gardening Glossary
Plain-language definitions for 120 common gardening terms, each with links to guides on this site.
120 terms · Alphabetized · Updated June 2026
A
The mechanical perforation of compacted soil or turf to improve gas exchange and water infiltration. Core aeration removes small plugs of soil with a hollow-tine aerator. Per Rutgers NJAES, fall core aeration of cool-season lawns reduces compaction, improves fertilizer uptake, and is often combined with overseeding and topdressing for best results.
Any material worked into soil to improve its physical structure, chemistry, or biology. Common amendments include compost, lime, sulfur, and gypsum. Per Penn State Extension, amendments are distinguished from fertilizers: amendments change the soil itself; fertilizers supply nutrients directly to plants.
A plant that completes its full life cycle—germination, flowering, seed set, and death—within a single growing season. Annuals must be replanted each year. Per NC State Extension, plants such as marigold, zinnia, and basil are true annuals; some tender perennials (impatiens, coleus) are grown as annuals in cold climates.
The pollen-bearing tip of a flower's stamen—the male reproductive organ of a flowering plant. Anthers release pollen grains that fertilize the ovule when transferred to a compatible stigma. Understanding anther structure is useful when hand-pollinating squash, corn, or sweet peppers.
Soft-bodied, pear-shaped insects (order Hemiptera) that feed by piercing plant tissue and extracting phloem sap. Most species measure 1–3 mm. Per UC IPM, populations can double in under a week in warm weather, causing leaf curl, honeydew deposits, and sooty mold. Many are controlled by lacewings, ladybugs, and parasitic wasps before intervention is needed.
B
A plant sold and shipped without soil around its roots, typically in a dormant state during late winter or early spring. Per UC Davis Cooperative Extension, bare-root trees and shrubs (roses, fruit trees, asparagus crowns) are cheaper than container-grown stock and establish quickly when planted correctly; they must be kept moist and planted before growth begins.
A plant that requires two growing seasons to complete its life cycle. In the first year it produces only vegetative growth (leaves, stems, roots); in the second it flowers, sets seed, and dies. Per Cornell Cooperative Extension, foxglove (*Digitalis purpurea*), hollyhock, and parsley are familiar biennials.
The rapid shift from vegetative growth to flowering and seed production triggered by heat, long days, or stress. In cool-season crops—lettuce, spinach, cilantro—bolting makes foliage bitter and inedible. Per University of Vermont Extension, selecting slow-bolt cultivars and timing plantings for cooler temperatures are the primary management strategies.
A slow-release organic fertilizer made from steamed and ground animal bones, typically analyzing around 3-15-0 (N-P-K) with significant calcium. Per Clemson HGIC, bone meal is used to promote root development and flowering; it is most effective in soils with pH below 7, where phosphorus is readily available to plant roots.
A modified leaf associated with a flower or flower cluster, often brightly colored and mistaken for a petal. In dogwood, poinsettia, and bougainvillea, the showy 'flowers' are actually bracts; the true flowers are small and inconspicuous at the center. Per Missouri Botanical Garden, bracts serve to attract pollinators in species with small, unshowy flowers.
The plant genus (family Brassicaceae) that includes cabbage, broccoli, kale, Brussels sprouts, kohlrabi, cauliflower, turnip, and mustard. Brassicas share a susceptibility to similar pests (cabbage worms, cabbage loopers, aphids) and diseases (clubroot, black rot). Per University of Maryland Extension, rotating brassicas out of the same bed for 3–4 years reduces soilborne pathogen buildup.
To spread seed, fertilizer, or granular pesticide evenly over a wide area rather than placing it in rows or holes. Broadcasting by hand or with a rotary spreader is the standard method for overseeding lawns and applying granular fertilizer. Per Penn State Extension, calibrating a spreader before each use prevents under- or over-application.
A compressed underground stem surrounded by fleshy, nutrient-storing scale leaves—the true bulb structure seen in tulips, daffodils, and alliums. In casual use, 'bulb' also covers corms (crocus, gladiolus), rhizomes (iris), and tubers (dahlia), though these are structurally distinct. Per NC State Extension, all true bulbs contain a complete embryonic plant ready to grow.
C
Yellowing of leaf tissue caused by insufficient chlorophyll, typically due to iron, manganese, or nitrogen deficiency, high soil pH, or waterlogged roots. Per Clemson HGIC, iron chlorosis in acid-loving plants (azalea, blueberry, gardenia) most often traces to soil pH above 6.5 blocking iron uptake, not to a true lack of iron in the soil.
An unheated, bottomless box with a transparent lid—typically glass or polycarbonate—that traps solar heat to extend the growing season. Per University of New Hampshire Cooperative Extension, a cold frame can add 4–6 weeks at both ends of the season in most temperate climates and is sufficient for hardening off seedlings or overwintering cold-hardy greens.
The practice of growing two or more plant species in proximity to gain mutual benefits—pest suppression, pollinator attraction, or efficient space use. Per Cornell Cooperative Extension, some companion relationships have documented evidence (basil reducing aphid loads near peppers in field trials) while others (the 'Three Sisters' of corn-bean-squash) have agronomic records going back centuries; many popular combinations lack controlled research support.
Decomposed organic matter—yard waste, food scraps, manure—stabilized by microbial activity into a dark, crumbly, humus-rich material. Per Penn State Extension, finished compost has a carbon-to-nitrogen ratio near 20:1, near-neutral pH, and no detectable pathogens or weed seeds when hot-composted above 131°F (55°C). It improves soil structure, water retention, and biological activity in both clay and sandy soils.
Any plant grown in a pot, planter, window box, or other above-ground vessel rather than in the ground. Per University of Illinois Extension, container plants dry out faster than in-ground plantings, require more frequent fertilization (nutrients leach with every watering), and need winter protection in zones where the root zone would freeze solid.
Describing plants or crops that grow best in cooler temperatures, typically 45–75°F (7–24°C), and struggle or bolt when summer heat arrives. Per Oregon State University Extension, cool-season vegetables (lettuce, spinach, peas, broccoli) are planted in early spring or fall; cool-season grasses (Kentucky bluegrass, tall fescue) go semi-dormant in summer heat.
A crop grown primarily to protect and improve the soil rather than for harvest—suppressing weeds, preventing erosion, fixing nitrogen (legume species), or adding organic matter when turned under. Per USDA NRCS, common cover crops include winter rye, crimson clover, and buckwheat; the choice depends on season, goal, and what follows in the rotation.
The junction between a plant's roots and stems, typically at or just below the soil surface. Per Penn State Extension, planting depth at the crown is critical: burying a tree's root flare or setting a peony crown deeper than 1-2 inches are among the most common causes of long-term decline. Most perennials should be planted so the crown sits at the same depth it occupied in the nursery.
A contraction of 'cultivated variety'—a plant selection maintained by vegetative propagation or controlled breeding for specific traits (flower color, disease resistance, mature size). Cultivar names appear in single quotes after the species name: *Hydrangea paniculata* 'Limelight'. Per the International Code of Nomenclature for Cultivated Plants, a cultivar must be distinct, uniform, and stable across generations.
D
A seedling disease complex caused by soilborne pathogens (Pythium, Rhizoctonia, Fusarium) that causes stems to collapse at the soil line, typically in cool, wet, poorly ventilated conditions. Per Cornell Cooperative Extension, the primary prevention is using sterile seed-starting mix, avoiding overwatering, providing adequate air circulation, and not replanting into infected media.
The removal of spent flowers before they set seed. This redirects the plant's energy from seed production back into vegetative growth or continued bloom. Per NC State Extension, deadheading is essential for reblooming perennials like salvia and coneflower; skipping it on species grown for ornamental seed heads (rudbeckia, echinacea) trades additional bloom for winter bird food.
Branches or stems in which the vascular tissue has died, recognizable by absence of leaves or absence of green tissue beneath the bark when scratched. Per RHS, removing deadwood is one of the few pruning tasks that can be done at any time of year without risk to the plant; it reduces disease entry points and weight hazards in larger trees.
Plants that shed all their leaves seasonally, typically in response to cold or drought. The term applies to trees, shrubs, and some perennials. Per Missouri Botanical Garden, most deciduous woody plants in temperate climates drop leaves in autumn after a photoperiod trigger, entering true dormancy; this is distinct from stress-induced leaf drop caused by drought or disease.
A growth habit in which a plant reaches a genetically fixed height, sets most of its fruit within a defined window, then stops growing. The term is most commonly applied to tomatoes. Per UC Davis Cooperative Extension, determinate tomatoes (also called bush tomatoes) typically reach 2–4 feet and ripen their crop over 2–4 weeks, making them useful for canning; indeterminate types keep growing and fruiting until frost.
The mechanical removal of thatch—the dense layer of living and dead stems, roots, and debris that accumulates between grass blades and soil. Per Rutgers NJAES, thatch deeper than ½ inch blocks water, air, and fertilizer penetration. Dethatching is done with a vertical mower or dethatching rake in early fall for cool-season grasses and late spring for warm-season types.
Having male and female flowers on separate individual plants, so two plants of different sexes are needed to produce fruit or seed. Per Missouri Botanical Garden, familiar dioecious landscape plants include holly (*Ilex* spp.), bayberry (*Morella*), and some viburnums; gardeners who want berries must plant at least one male pollinator within range of the females.
Planting seeds directly into the garden bed where plants will grow, rather than starting them in trays indoors. Per Cornell Cooperative Extension, crops that develop taproots (carrot, beet, parsnip, radish) or dislike transplanting (peas, beans, squash) should be direct-sown; timing relative to the last frost date determines success.
A propagation method in which a mature clump of herbaceous perennial is dug up, split into sections, and replanted. Per University of Minnesota Extension, division simultaneously rejuvenates the parent plant (which can decline in the center with age), multiplies stock, and is the preferred method for propagating cultivars that do not come true from seed.
A period of metabolic slowdown in which a plant suspends active growth, triggered by cold, drought, or shortening day length. True dormancy is a protective physiological state distinct from stress-induced wilting or dieback. Per Penn State Extension, breaking dormancy prematurely by moving a plant indoors over winter can exhaust its carbohydrate reserves and weaken it.
A watering system that delivers water directly to the root zone through emitters, tubes, or porous hose at slow, controlled rates. Per UC IPM, drip irrigation reduces foliar disease pressure by keeping leaves dry, minimizes evaporation, and can reduce water use by 30–50% compared to overhead sprinklers in vegetable gardens.
The imaginary circle on the ground directly below the outermost tips of a tree's or shrub's branches. Per University of Florida IFAS, the majority of a tree's feeder roots are concentrated in the top 12–18 inches of soil within and just beyond the drip line—not near the trunk—which is why fertilizer, mulch, and irrigation should be directed to this zone rather than the base.
E
A plant that retains functional leaves year-round, shedding old foliage gradually rather than all at once in autumn. Per Missouri Botanical Garden, evergreens include both broadleaf species (rhododendron, holly, boxwood) and needled conifers (pine, spruce, arborvitae); in cold climates, broadleaf evergreens often suffer winter burn when frozen soil prevents water uptake.
The combination of light intensity, duration, and direction a planting site receives, typically classified as full sun, partial sun/shade, or full shade. USDA plant tag definitions (used as standard by most extension services): full sun = 6+ hours direct sun; partial sun/shade = 3–6 hours; full shade = under 3 hours. Wind and reflected heat from walls can modify effective exposure significantly.
F
The first-generation offspring of a controlled cross between two distinct, inbred parent lines. Per Clemson HGIC, F1 hybrids are prized in vegetable breeding for hybrid vigor (heterosis), disease resistance, and uniformity; seed saved from an F1 plant will not produce plants identical to the parent, which is why gardeners who want seed-saving ability choose open-pollinated or heirloom varieties instead.
Leaf margin scorch, tip dieback, or root damage caused by excess soluble salts from over-application of synthetic fertilizer. Per Penn State Extension, salt draws water out of root cells by osmosis, effectively causing drought stress even in moist soil. Watering in heavily before and after application, and following label rates, prevents burn; organic slow-release fertilizers carry lower burn risk.
Applying dilute liquid fertilizer or micronutrient solution directly to leaves so nutrients are absorbed through the leaf surface. Per University of Maryland Extension, foliar feeding is most useful for correcting acute micronutrient deficiencies (iron, manganese, zinc) when soil conditions prevent uptake; it is not a substitute for adequate soil fertility and should be done in early morning to reduce leaf burn risk.
Describing soil that crumbles easily in the hand, with a loose, open texture that allows roots to penetrate freely and excess water to drain. Per Cornell Cooperative Extension, friability is achieved by consistent additions of organic matter; it deteriorates when soil is tilled wet or subjected to heavy foot traffic, which destroys the aggregate structure that makes soil crumble.
The average calendar date on which a location expects its last spring frost or first autumn frost, based on 30-year NOAA historical records. Per NOAA, 'average last frost date' represents the 50% probability date—not a guarantee; the 10% and 90% probability dates bracket a wider safe planting window. Frost dates are expressed by ZIP code and are the foundation of all seeding and transplanting schedules.
A site receiving fewer than 3 hours of direct sun per day, with the remainder in deep shade. Per NC State Extension, very few flowering plants thrive in true full shade; most 'shade plants' actually prefer partial shade with some morning sun. Genuine full-shade options include ferns, hostas, wild ginger, and epimedium.
A site receiving 6 or more hours of direct, unfiltered sunlight per day. Per USDA Plant Database definitions used by most extension services, full sun is the minimum requirement for most vegetable crops, many herbs, and the majority of flowering perennials and shrubs. Morning sun with afternoon shade can substitute for full sun in hot climates where afternoon temperatures exceed 95°F.
A chemical or biological agent applied to prevent or treat fungal disease in plants. Per UC IPM, fungicides are most effective as protectants applied before infection occurs; they have limited curative action once fungal mycelium is established in tissue. OMRI-listed options include copper, sulfur, and Bacillus subtilis-based products; synthetic options include chlorothalonil and myclobutanil.
G
The resumption of active growth by a seed embryo after dormancy, beginning with water uptake (imbibition) and ending when the seedling's radicle (primary root) emerges. Per Cornell Cooperative Extension, germination requires species-specific temperature, moisture, and sometimes light conditions; soil temperature—not air temperature—is the critical variable for vegetable seeding.
Genetically Modified Organism: a plant, animal, or microorganism whose genome has been altered by inserting, deleting, or modifying specific genes using recombinant DNA techniques. Per USDA NRCS, no GMO varieties are currently sold to home gardeners in the US retail seed market; all garden seed labeled 'non-GMO' is making a distinction from commercial agricultural crops (mostly corn, soy, cotton, canola).
Describing a plant composed of two genetically distinct parts: a scion (the desired above-ground variety) fused onto a rootstock (selected for disease resistance, vigor, or size control). Per University of Florida IFAS, grafted tomatoes on disease-resistant rootstocks can significantly reduce losses from soilborne pathogens (Fusarium, Verticillium, nematodes) in infested beds; grafted fruit trees control mature size and speed fruiting.
Low-growing plants used to cover bare soil, suppress weeds, prevent erosion, and reduce maintenance needs in areas where lawn grass is impractical—dense shade, slopes, or dry spots. Per North Carolina State Extension, effective ground covers for shade include pachysandra, epimedium, and sweet woodruff; for sun, creeping thyme and sedum are workhorses.
H
The gradual acclimatization of seedlings started indoors to outdoor conditions—direct sun, wind, temperature fluctuation—before transplanting. Per Penn State Extension, skipping hardening off is one of the top causes of transplant failure; the process typically takes 7–10 days, beginning with 1–2 hours of morning shade and slowly increasing sun and wind exposure.
A geographic area defined by average annual minimum winter temperature, used to predict whether a plant can survive winter outdoors. The 2023 USDA Plant Hardiness Zone Map divides the US into 13 zones in 10°F increments (plus half-zones). Per USDA ARS, zone maps indicate cold hardiness only; heat tolerance, humidity, and soil drainage are equally important for long-term plant survival.
An open-pollinated plant variety passed down for at least 50 years before commercial hybrid breeding became dominant. Per Seed Savers Exchange, heirloom vegetables produce seed that comes true to type, allowing annual seed-saving; they are valued for flavor, regional adaptation, and genetic diversity, though many lack the disease resistance of modern hybrids.
A plant whose above-ground stems and leaves die back to the ground each winter rather than forming persistent woody tissue. Per Missouri Botanical Garden, most perennials in temperate gardens are herbaceous (hosta, peony, rudbeckia); they regrow each spring from underground roots, rhizomes, or crowns. 'Herbaceous border' specifically means a planted bed without woody shrubs.
A chemical used to kill or suppress plants. Pre-emergent herbicides prevent weed seed germination; post-emergent herbicides kill emerged weeds. Per UC IPM, selective herbicides target specific plant types (grasses vs. broadleaves) while non-selective herbicides (glyphosate) kill most green tissue they contact. Proper timing, rate, and target identification are essential to avoid damage to desirable plants.
A plant species that provides food and/or habitat for a specific insect, typically used in the context of caterpillar host plants for butterfly and moth species. Per Xerces Society, host plants are distinct from nectar plants: monarch caterpillars can only eat milkweed (*Asclepias* spp.); black swallowtail caterpillars require plants in the carrot family (parsley, dill, fennel).
The stable, dark fraction of soil organic matter that remains after decomposition has largely run its course—distinct from fresh compost or partially broken-down material. Per USDA Natural Resources Conservation Service, humus improves soil structure, acts as a slow-release nutrient reservoir, and supports the cation exchange capacity that holds calcium, magnesium, and potassium available to roots.
A plant produced by crossing two genetically distinct parent plants, whether naturally or through controlled breeding. Hybrids may show improved vigor, uniformity, or disease resistance compared to either parent (a phenomenon called heterosis). Per NC State Extension, the word 'hybrid' on a seed packet does not mean GMO—all F1 hybrid vegetables are produced by conventional cross-pollination.
I
A growth habit in which a plant continues growing and producing fruit throughout the season until killed by frost or disease—the opposite of determinate. Per UC Davis Cooperative Extension, indeterminate tomatoes (most heirloom and many modern varieties) can reach 6–10 feet on a stake and require ongoing pruning and support; they produce a continuous harvest over months rather than a single concentrated set.
A pesticide formulated from potassium salts of fatty acids that kills soft-bodied insects (aphids, mites, mealybugs, whiteflies) by disrupting cell membranes on contact—it has no residual activity. Per Clemson HGIC, commercial insecticidal soap (e.g., Safer Brand) is OMRI-listed for organic use; homemade dish soap mixtures are inconsistent and can burn foliage because dish soap contains degreasers not present in true insecticidal soap.
A substance used to kill insects at any life stage. Per UC IPM, insecticides are categorized by mode of action (contact, systemic, stomach poison) and spectrum (broad-spectrum vs. selective). Broad-spectrum insecticides kill beneficial insects including pollinators and natural enemies alongside target pests; targeted applications during early morning or evening, when pollinators are less active, reduce non-target harm.
Integrated pest management (IPM)
A decision-making framework for managing pests that prioritizes prevention, monitoring, and the least-toxic effective intervention, rather than routine pesticide application. Per USDA NRCS, IPM combines cultural controls (crop rotation, resistant varieties, sanitation), biological controls (beneficial insects), physical controls (row covers, traps), and chemical controls used only when monitoring confirms pest populations exceed economic or aesthetic thresholds.
The sections of a plant stem between two successive nodes (the points where leaves, buds, or branches attach). Per University of California Cooperative Extension, abnormally long internodes—'leggy' growth—indicate insufficient light or excessive nitrogen; plants stretch toward light, producing weak stems with leaves spaced too far apart for sturdy structure.
A non-native species that spreads aggressively beyond its planting site, displacing native plants and disrupting ecological function. Per USDA National Invasive Species Information Center, invasive status is state-specific—butterfly bush (*Buddleja davidii*) is regulated in Oregon and Washington but not prohibited in most Eastern states; always check your state's invasive species list before planting. Invasiveness is distinct from aggressive behavior in a garden setting.
L
The immature, worm-like stage of insects that undergo complete metamorphosis (holometabolism)—butterflies, beetles, flies, and wasps all pass through a larval stage before pupating into adults. Per UC IPM, most insect feeding damage on garden plants is done by larvae, not adults; identifying the specific larva (caterpillar, grub, leafminer) determines the correct management approach.
The downward movement of water-soluble nutrients through the soil profile, beyond the reach of plant roots. Per Penn State Extension, leaching is most severe in sandy soils and during heavy rain or over-irrigation; nitrogen (as nitrate) is the nutrient most vulnerable because it carries a negative charge and is not held by soil particles. Slow-release fertilizers and organic amendments reduce leaching losses.
Partially decomposed leaves, used as a lightweight soil conditioner and mulch. Per RHS (Royal Horticultural Society), leaf mold is made by piling fallen leaves in a wire cage and leaving them for 1–2 years; the result improves moisture retention in sandy soils, adds slow-release nutrients, and supports beneficial fungal communities. It is a lower-fertility amendment than compost but excellent as a surface mulch.
A member of the family Fabaceae (peas, beans, clover, alfalfa, vetch), distinguished by root nodules hosting *Rhizobium* bacteria that fix atmospheric nitrogen into plant-available ammonium. Per USDA ARS, inoculating legume seeds with the appropriate *Rhizobium* strain at planting increases nitrogen fixation; the residue left after harvest enriches soil for subsequent crops.
A soil texture class containing roughly equal proportions of sand, silt, and clay particles, generally defined as 25–50% sand, 25–50% silt, and 10–25% clay. Per USDA Soil Survey Manual, loam drains well while retaining adequate moisture, warms quickly in spring, and supports root penetration—the standard against which all other soil textures are compared. Most plants grow best in loam or sandy loam.
M
A localized area where temperature, humidity, wind exposure, or moisture differs measurably from the surrounding region's climate. Per Penn State Extension, south-facing walls store and radiate heat to create warmer microclimates (extending the growing season or allowing marginally hardy plants), while low spots collect cold air on still nights and frost earlier than the surrounding landscape.
Having separate male and female flowers on the same plant, so a single individual can self-pollinate. Per Missouri Botanical Garden, most cucurbits (squash, cucumber, melon, pumpkin) are monoecious; the first flowers to appear are usually male and will drop without setting fruit—a fact that confuses new gardeners who mistake normal male flower drop for a pollination failure.
Any material applied over soil to moderate temperature, retain moisture, suppress weeds, and (for organic mulches) improve soil structure as it decomposes. Per Penn State Extension, organic mulches (shredded bark, wood chips, straw) are preferred over inorganic (rubber, gravel) for ornamental and vegetable beds; a 2–3 inch layer is optimal—thicker piles can cause anaerobic conditions and stem rot.
A cone-shaped mound of mulch piled directly against a tree's trunk—universally discouraged by arborists. Per Penn State Extension, mulch volcanoes keep trunk bark perpetually moist, promoting rot, fungal cankers, and secondary root girdling; correct practice is a 2-3 inch layer extending to the drip line with a 3-6 inch gap at the trunk flare.
N
A species that evolved in a given region and was present before European colonization in North American contexts. Per Xerces Society, native plants support 10–50 times more native bee species than non-native ornamentals; Dr. Doug Tallamy's research (University of Delaware) shows native oaks alone support over 550 caterpillar species versus fewer than 5 for most introduced ornamentals.
To spread and reproduce on their own in a site over time, forming self-sustaining colonies without annual replanting. Per University of Vermont Extension, naturalizing bulbs (daffodil, crocus, scilla) are species that perennialize and multiply in the right conditions; naturalizing is distinct from invasive spread—it refers to behavior within a managed garden setting rather than escape into wild areas.
A botanical insecticide, fungicide, and miticide derived from the seeds of the neem tree (*Azadirachta indica*). The active compound azadirachtin disrupts insect molting and reproduction. Per Clemson HGIC, neem oil is OMRI-listed for organic use, effective against aphids, spider mites, and some fungal diseases when applied thoroughly to both leaf surfaces; it breaks down rapidly in sunlight and has low toxicity to mammals and birds.
Microscopic roundworms (phylum Nematoda) found in virtually all soils. Plant-parasitic nematodes (root-knot, cyst, lesion species) damage roots; beneficial entomopathogenic nematodes are applied to soil to control soil-dwelling insect larvae. Per University of Florida IFAS, root-knot nematodes (*Meloidogyne* spp.) are a major constraint in sandy, warm-climate vegetable gardens; resistant varieties and crop rotation are primary management tools.
The three-number ratio on every fertilizer label representing the percentage by weight of nitrogen (N), phosphorus (P as P₂O₅), and potassium (K as K₂O). Per Penn State Extension, nitrogen drives vegetative growth; phosphorus supports root development and flowering; potassium improves stress tolerance, water regulation, and disease resistance. A 10-10-10 fertilizer is 10% each of all three; a 46-0-0 (urea) is pure nitrogen.
O
A seed variety that produces offspring genetically similar to the parent when pollinated by the same variety, whether by wind, insects, or hand. Per Seed Savers Exchange, open-pollinated seeds (including heirlooms) can be saved and replanted reliably; they are distinct from F1 hybrids, which do not breed true.
The living and dead biological material in soil—microbes, plant roots, fungi, partially decomposed residue, and humus. Per USDA NRCS, increasing soil organic matter from 1% to 3% roughly doubles a loam soil's water-holding capacity and significantly improves both drainage in clay and moisture retention in sand. Most agricultural soils in the eastern US contain 1–5% organic matter.
The practice of spreading grass seed over an existing lawn to thicken thin or bare areas without killing or removing existing turf. Per Rutgers NJAES, overseeding is most effective when done in early fall for cool-season grasses after core aeration, which gives seed direct soil contact; seed-to-soil contact is the single most important factor in germination success.
To keep a tender plant alive through a winter it would not naturally survive in your climate—typically by digging and storing dormant roots, moving container plants indoors, or providing protective structures. Per Penn State Extension, overwintering strategy depends on the plant's cold hardiness and dormancy requirements; dahlias, cannas, and tender geraniums are commonly overwintered in temperate gardens.
P
A site receiving 3–6 hours of direct sun per day, with shade during the hottest afternoon hours. Per NC State Extension, many plants labeled 'partial shade' actually need at least 4 hours of direct morning sun for good flowering; afternoon sun in hot climates counts for less because it is more intense than morning sun and may stress shade-adapted species.
Functionally equivalent to partial shade (3–6 hours of direct sun per day); plant tags use either term to describe the same condition. In practice, 'partial sun' often implies that a plant prefers the higher end of the 3–6 hour range and can handle some direct afternoon exposure, while 'partial shade' implies preference for the lower end with protection from afternoon sun.
Partially decomposed sphagnum moss harvested from peat bogs, used as a soil amendment and in seed-starting mixes for its acidity (pH 3.5–4.5), moisture retention, and sterility. Per RHS, peat extraction is controversial because peat bogs are significant carbon sinks that form over thousands of years; coco coir is the most common sustainable alternative for seed starting.
A plant that lives for three or more years, returning each spring from a persistent root system (herbaceous perennials) or from permanent woody structure (woody perennials—trees and shrubs). Per NC State Extension, a plant is considered reliably perennial only within the USDA hardiness zone range in which its roots survive winter; a geranium that's perennial in zone 9 is an annual in zone 6.
A measure of soil acidity or alkalinity on a logarithmic scale from 0 to 14, with 7 as neutral. Per Penn State Extension, most garden plants grow best in the 6.0–7.0 range; outside this range, nutrients become chemically unavailable even when present in the soil. Each pH unit represents a tenfold change in hydrogen ion concentration—pH 5.0 is 10 times more acidic than pH 6.0.
The duration of light and darkness in a 24-hour cycle, which regulates flowering, dormancy, and other developmental events in many plants. Per UC Davis, short-day plants (chrysanthemum, poinsettia) flower when nights exceed a critical length; long-day plants (spinach, lettuce) bolt and flower as days lengthen in summer; day-neutral plants (tomato, cucumber) are not triggered by photoperiod.
The transfer of pollen from an anther to a compatible stigma, enabling fertilization and seed or fruit development. Per USDA ARS, pollination may be accomplished by wind (corn, grass), insects (most fruits and vegetables), birds, or bats. Many vegetable crops are self-pollinating but benefit from vibration—bumble bee buzz pollination substantially increases tomato and pepper fruit set in greenhouse conditions.
A herbicide applied to soil before weed seeds germinate, creating a chemical barrier that kills seedlings as they emerge. Per NC State Extension, timing is critical: pre-emergents must be applied and watered in before soil temperature reaches the germination threshold for the target weed (55°F for crabgrass, measured at 2-inch depth on 3 consecutive days). They have no effect on established weeds.
Any method of producing new plants—from seed (sexual propagation) or from vegetative parts such as cuttings, divisions, layering, or grafting (asexual propagation). Per Cornell Cooperative Extension, asexual propagation produces plants genetically identical to the parent (clones), which is necessary to preserve named cultivars; sexual propagation from seed produces genetic variation and is the basis of plant breeding.
To selectively remove plant parts—stems, branches, roots, spent flowers—to improve health, shape, flowering, or structure. Per RHS, pruning is plant-specific: timing a cut incorrectly on a spring-blooming shrub (lilac, forsythia) removes the following year's flower buds; the correct timing depends on whether the plant blooms on old wood or new wood.
R
An unbranched flower cluster in which individual flowers are attached to a central stalk by short stems (pedicels), with the oldest flowers at the base and youngest at the tip. Per Missouri Botanical Garden, familiar raceme-bearing plants include foxglove (*Digitalis*), lupine (*Lupinus*), and salvia; deadheading a raceme at the right stage can trigger secondary branching and rebloom.
A garden bed built above the surrounding ground level, typically framed with wood, metal, or concrete, and filled with a custom growing mix. Per Rutgers NJAES, raised beds warm faster in spring, drain better than most native soils, and allow precise control of soil composition; they are especially valuable where native soil is compacted, poorly drained, or contaminated.
A horizontal underground or near-surface stem that stores nutrients and produces new shoots and roots at nodes, enabling spreading and vegetative propagation. Per Missouri Botanical Garden, bearded iris, lily of the valley, running bamboo, and many lawn grasses spread by rhizomes. Dividing rhizomatous plants requires cutting the rhizome into sections, each with at least one viable growth node.
A condition in which a container plant's roots have filled the pot, circling around the inside walls and restricting further growth. Per University of Illinois Extension, severely root-bound plants show wilting despite adequate water, stunted growth, and roots emerging from drainage holes; corrective action involves either repotting to a larger container or, for ground planting, scoring and loosening the root ball to encourage outward growth.
A circular arrangement of leaves radiating from a central growing point at or near soil level, often characteristic of the first-year vegetative stage of biennials or the basal growth of some perennials. Per NC State Extension, many weeds (dandelion, plantain) form rosettes that are difficult to control because the growing point is close to the soil surface and survives mowing.
Water that flows over the soil surface rather than infiltrating, carrying nutrients, pesticides, and sediment into storm drains and waterways. Per USDA NRCS, runoff from over-fertilized lawns and gardens is a primary source of phosphorus pollution in freshwater; practices that reduce runoff include applying fertilizer according to soil test results, maintaining organic matter to improve infiltration, and using rain gardens to capture and infiltrate runoff.
S
The coarsest soil particle size class (0.05–2.0 mm diameter), providing drainage and aeration but holding little water or nutrients. Per USDA Soil Survey Manual, sandy soils warm quickly in spring but dry out rapidly and leach nutrients; they benefit from regular additions of organic matter. Adding sand to clay soil without adding organic matter creates a concrete-like mix—a common and counterproductive mistake.
The mechanical or chemical breaking of a hard seed coat to allow water uptake and trigger germination. Per University of Minnesota Extension, seeds with impermeable coats (sweet pea, morning glory, baptisia, moonflower) may not germinate reliably without scarification; methods include nicking with a file, rubbing with sandpaper, or brief soaking in warm water.
The two-part Latin binomial (genus + species) that uniquely identifies a plant species worldwide, regardless of regional common names. Per International Code of Nomenclature for algae, fungi, and plants, scientific names are italicized: *Hydrangea macrophylla*, *Acer palmatum*. Common names vary by region and can apply to multiple unrelated plants; the scientific name is the only reliable identifier when purchasing specific plants.
A young plant in the early stage of growth, typically from germination through the development of the first true leaves (as distinct from the seed leaves, or cotyledons). Per Penn State Extension, seedlings are most vulnerable to damping off, desiccation, and cold damage; they should not be transplanted outdoors until they have developed 2–4 true leaves and have been properly hardened off.
The ability of a plant to drop viable seed that germinates and produces new plants the following season without gardener intervention. Per NC State Extension, self-seeding annuals and short-lived perennials (foxglove, larkspur, black-eyed Susan, nicotiana) can maintain a colony indefinitely; leaving seed heads in place in autumn is necessary to allow seed dispersal. Self-seeded offspring from hybrid cultivars may not resemble the parent.
To apply fertilizer alongside growing plants by scratching or banding granules into the soil surface beside the row or plant stem, then watering in. Per University of Maine Cooperative Extension, side-dressing is the standard mid-season nitrogen application method for corn, tomatoes, and other heavy feeders; it delivers nutrients where active roots are feeding without disturbing the root zone.
A fertilizer formulation designed to release nutrients gradually over weeks or months, reducing the risk of fertilizer burn and leaching, and lowering application frequency. Per Penn State Extension, slow-release mechanisms include sulfur-coated urea, polymer-coated granules, and natural organic materials (feather meal, composted manure); IBDU and methylene urea release is temperature-driven and slows in cold soil.
The rate at which water moves through soil and away from the root zone. Per Clemson HGIC, drainage is assessed with a simple perc test: fill a 12-inch-deep hole with water, let it drain, refill, then measure the drop over one hour; well-drained soil loses 1-3 inches per hour. Most root rot problems trace to poor drainage rather than overwatering at the surface.
A laboratory or field analysis of soil pH, nutrient levels (phosphorus, potassium, calcium, magnesium), organic matter, and often lead content. Per Penn State Extension, a soil test is the only accurate basis for fertilizer and lime recommendations; guessing application rates without a test wastes money and risks nutrient imbalances or runoff. Most state university Extension labs analyze samples for $10–20.
Pre-treatment of seeds by exposing them to moist cold (cold stratification) or warmth to break physiological dormancy and trigger germination. Per University of Minnesota Extension, seeds from temperate perennials and trees often require 4–12 weeks at 35–40°F in moist media before they will germinate; this mimics winter burial conditions and is typically done in a sealed plastic bag with moist peat or vermiculite in the refrigerator.
A plant with thick, fleshy leaves, stems, or roots that store water as an adaptation to arid or seasonally dry conditions. Per University of Arizona Cooperative Extension, succulents native to the American Southwest (agave, yucca, sedum) are adapted to well-drained, low-fertility soils; the primary killer of succulents in humid climates is overwatering combined with poor drainage, not cold.
T
A single, dominant primary root that grows directly downward from the base of the stem, with smaller lateral roots branching from it. Per NC State Extension, taprooted plants (carrot, parsnip, dandelion, baptisia) transplant poorly because cutting the taproot is often fatal or severely setback-inducing; they should be direct-sown or transplanted as very small seedlings before the taproot becomes substantial.
The layer of living and dead stems, roots, stolons, and rhizomes that accumulates between grass blades and the soil surface. Per Rutgers NJAES, a thin thatch layer (under ½ inch) is beneficial—it cushions traffic and moderates soil temperature; thatch exceeding ½ inch blocks water, fertilizer, and air penetration and provides habitat for disease pathogens and insect pests.
The removal of some seedlings from an overcrowded stand to give the remaining plants adequate space for root development and air circulation. Per University of Vermont Extension, thinning is non-negotiable for carrots, beets, and other root vegetables—crowded plants produce deformed, small roots regardless of fertility. Thinning to labeled spacing is consistently one of the most-skipped and most-consequential tasks in vegetable gardening.
The physical condition of soil as it relates to ease of cultivation and suitability for plant growth—its friability, structure, aggregate stability, and drainage. Per USDA NRCS, good tilth means the soil crumbles easily, holds its structure when wet, drains freely without becoming waterlogged, and supports root penetration without compaction. Tilth is improved by organic matter and biological activity, and degraded by tillage in wet conditions.
To apply compost, fertilizer, or soil amendment directly on the surface of an existing bed or lawn without incorporating it into the soil. Per Penn State Extension, topdressing lawns with compost (⅛–¼ inch layer) after aeration improves soil biology and organic matter over time; topdressing perennial beds in fall protects crowns and gradually improves soil as material decomposes.
To move a plant from one growing location to another—from seed tray to pot, pot to garden, or one garden spot to another. Per University of Maryland Extension, transplanting is most successful in cool, overcast weather or late afternoon; disturbing roots as little as possible, watering in with a dilute starter fertilizer solution, and providing temporary shade for wilting-prone species reduce transplant shock.
A swollen, starchy underground stem segment that stores nutrients and produces new growth from 'eyes' (axillary buds). The potato is the most familiar example; dahlias produce tuberous roots (similar but technically modified roots rather than stems). Per University of Florida IFAS, tubers are distinguished from bulbs by the absence of scale leaves—they are solid storage tissue throughout.
U
Informal shorthand for a plant's assigned USDA Plant Hardiness Zone—the zone indicating the coldest average minimum temperature a plant will survive. Zone numbers range from 1 (coldest, average minimum below -50°F) to 13 (tropical, above 60°F). Per USDA ARS, the 2023 revised map updated zone boundaries for about 50% of US ZIP codes, reflecting warming trends in 30-year climate data.
V
In botanical usage, a naturally occurring subdivision of a species below the rank of subspecies, designated with 'var.' (e.g., *Hydrangea macrophylla* var. *normalis*). In common gardening use, 'variety' is used interchangeably with 'cultivar'—though strictly these differ: cultivars are human-selected and maintained; botanical varieties arise in the wild. Per the International Code of Botanical Nomenclature, the distinction matters in plant registration but is rarely critical for gardeners.
Worm castings produced by feeding organic matter (kitchen scraps, paper, yard waste) to red wigglers (*Eisenia fetida*) in a controlled bin. Per Cornell Cooperative Extension, vermicompost is richer in plant-available nutrients and beneficial microbial activity than conventional compost; studies show it suppresses some soilborne pathogens and improves seedling establishment when used as a seed-starting amendment or top-dressing.
The requirement for a prolonged period of cold temperatures to trigger flowering or germination. Per Cornell Cooperative Extension, biennial vegetables like parsley bolt in their second season only after experiencing winter cold; bulbs such as tulips require vernalization to flower reliably. Pre-chilling bulbs in the refrigerator replicates natural vernalization for gardeners in mild climates.
W
The practice of thoroughly watering immediately after planting seeds, transplants, or dry amendments to ensure soil contact, prevent air pockets, and initiate root establishment. Per Penn State Extension, watering in also moves soluble fertilizer to the root zone and is essential after applying granular pre-emergent herbicide, which requires moisture to activate its soil chemistry.
Any plant growing where it is not wanted. The term has no botanical meaning—dandelion is a weed in a lawn but a useful pollinator resource in a meadow planting. Per USDA NRCS, weeds compete with crops for water, nutrients, and light; perennial weeds with deep taproots or rhizomes (Canada thistle, bindweed, quackgrass) are significantly harder to eradicate than annual weeds, which die after setting seed.