Geranium Care: Annual Pelargoniums vs Hardy Cranesbills
The word "geranium" is applied to two unrelated plants — annual Pelargonium and hardy perennial cranesbill Geranium spp. Care requirements differ substantially; this guide covers both.
Pelargoniums vs. hardy geraniums: identifying what you have
The confusion between these two plants has a historical root. Swedish botanist Carl Linnaeus originally classified both under Geranium; they were later split when their differences became clear. The common name "geranium" stuck to Pelargonium in popular use, and it's never been untangled. Per Clemson Extension HGIC, the "common geranium sold in most garden centers" is botanically Pelargonium × hortorum.
Annual "geraniums" — Pelargonium × hortorum and relatives
Identifying features: Round-headed flower clusters in red, pink, salmon, coral, or white on upright stems 12–24 inches tall. Thick, round-lobed leaves often with a darker "horseshoe" band. Distinctive spicy or musky scent when leaves are bruised. These are the window-box geraniums, the bedding plants, the porch pot staples.
There are also ivy geraniums (Pelargonium peltatum), with trailing stems suited to hanging baskets, and scented-leaf geraniums (Pelargonium graveolens and others) grown for fragrant foliage. All share the same basic care requirements.
Hardiness: Perennial only in USDA zones 10–11. In zones 3–9, they are grown as annuals or overwintered indoors.
Hardy geraniums (cranesbills) — Geranium spp.
Identifying features: Smaller, more delicate five-petaled flowers in purple, blue, pink, magenta, or white, often with visible veining. Deeply lobed palmate leaves on low-mounding plants, typically 12–18 inches tall. Many have good fall foliage color. No strong scent. 'Rozanne', 'Johnson's Blue', 'Biokovo', and Geranium sanguineum are common landscape varieties.
Hardiness: Most are hardy in zones 3–8 or 4–9 depending on species. They go dormant in winter and re-emerge reliably in spring.
USDA hardiness and where each grows
Pelargonium can be grown as a garden annual in all zones 2–11. It thrives in the Mediterranean-like summers of zones 7–10 and performs well as a container plant everywhere with regular watering and feeding. Per Clemson Extension HGIC, pelargoniums "grow best in mild climates" and suffer in both extended high heat above 90°F and cool temperatures below 45°F.
Hardy geraniums are reliable perennials across zones 3–9. Geranium sanguineum (bloody cranesbill) is among the most adaptable, thriving in zones 3–8 across a wide range of soils and sun exposures. 'Rozanne' (Geranium × 'Rozanne') is widely considered the best all-around hardy geranium, with an exceptional bloom period from early summer through frost.
Light
For Pelargonium: full sun to part shade. In zones below 7, full sun (6+ hours) produces the most vigorous bloom. In zones 8–10, afternoon shade prevents heat-induced dormancy, which causes plants to stop blooming in midsummer. Most growers in the South find pelargoniums perform better in light shade than in baking full sun.
For hardy geraniums: most species prefer full sun to light shade. Geranium macrorrhizum and 'Biokovo' are notably shade-tolerant — useful in dry shade under trees where most plants struggle. 'Rozanne' blooms longest and most heavily in full sun but tolerates significant shade.
Watering
Pelargoniums are drought-tolerant once established and are killed faster by overwatering than by underwatering. They evolved in seasonally dry South Africa. The standard rule: water when the soil surface is dry, then water thoroughly; never let containers sit in a saucer of standing water. Per Clemson Extension HGIC, "overwatering causes root rot," which is the most common fatal mistake with pelargoniums.
In containers, this means checking daily in summer heat — a 10-inch pot in full sun may need water every day. In garden beds, an established pelargonium needs watering only during extended dry spells. Water at the base, not overhead; wet foliage invites botrytis.
Hardy geraniums are considerably more drought-tolerant than pelargoniums once established. Most cranesbills need supplemental water only in the first growing season after planting. Geranium sanguineum in particular is considered drought-hardy in many extension publications.
Soil and pH
Both types prefer well-draining soil with moderate fertility. Heavy, wet soil is fatal to pelargoniums and hard on cranesbills. A pH of 6.0–7.0 suits both. Per Penn State Extension, pelargoniums "grow best in a moderately fertile, well-drained soil" — excessive fertility produces lush foliage at the expense of flowers.
For container pelargoniums, a quality potting mix (not garden soil) with added perlite to improve drainage outperforms most in-ground planting unless your garden soil is already sandy and well-drained.
Planting
Transplant pelargoniums outdoors after the last frost date when nighttime temperatures are reliably above 45°F. They are frost-sensitive and will suffer even at temperatures in the high 30s. Set transplants at the same depth as their nursery container. Space 10–12 inches apart for bedding; 6–8 inches in containers for a quick fill.
Hardy geraniums can be planted in spring or fall. Fall planting in zones 5–7 allows roots to establish before winter and produces larger, more vigorous plants in the first full season. Space most cranesbills 18–24 inches apart — they spread by rhizome over time and fill in generously without being invasive.
Fertilizing
Pelargoniums in containers benefit from regular feeding — a water-soluble balanced fertilizer (10-10-10 or 20-20-20 at half strength) every two weeks produces strong continuous bloom. In-ground plants need less: a slow-release balanced fertilizer at planting time is often sufficient for the season. Per Clemson Extension HGIC, avoid high-nitrogen fertilizers that "favor vegetative growth over flower production."
Hardy geraniums are low-maintenance feeders. A light top-dressing of compost in spring is all most established cranesbills need. They perform well in average garden soils without supplemental fertilizer.
Deadheading and pruning
Pelargoniums benefit from regular deadheading — removing spent flower stalks at the base, not just picking off the petals. This redirects energy to new bud formation and prevents seed set, which can reduce continuous bloom. Per Penn State Extension, deadheading "promotes a neat appearance and encourages continuous bloom."
In midsummer, if plants have become leggy (long bare stems with foliage only at the tips), a hard cutback by one-third to one-half will reinvigorate them. New growth and flower buds emerge within 2–3 weeks.
Hardy geraniums: 'Rozanne' and most other long-blooming types benefit from cutting back by half in midsummer when they look spent — they typically rebloom within 3–4 weeks. Geranium sanguineum and others can simply be sheared back after their main flush; they will re-emerge fresh and often produce a secondary bloom in fall.
Overwintering pelargoniums
Two methods work reliably. The simplest: pot up garden-grown plants or bring containers indoors in late September, before frost. Grow them in a sunny window (or under grow lights) as houseplants through winter. They won't look spectacular, but they'll survive and can go back outside in spring.
The traditional method: lift plants, shake off soil, and store bare-root in paper bags or hung upside down in a cool (45–50°F), dark, frost-free space such as an unheated basement or garage. About once a month, soak the roots in water for an hour and re-dry. Per University of Minnesota Extension, this technique "can work well if storage conditions are right" but is less reliable than growing as houseplants for most gardeners.
Common problems
Botrytis blight (gray mold)
Fuzzy gray mold on flowers and stems, most common in cool, humid weather with poor air circulation. Remove infected tissue immediately. Per UC IPM, preventive applications of copper-based fungicide and improving air circulation are the primary management strategies. Do not compost infected material.
Bacterial leaf spot (Xanthomonas)
Water-soaked spots with yellow halos on leaves, eventually turning brown and dry. Per Penn State Extension, bacterial leaf spot is spread by overhead watering and infected transplants. There is no cure — remove infected leaves, avoid wetting foliage, and purchase certified disease-free transplants.
Geranium (Pelargonium) rust
Orange-brown pustules on leaf undersides, yellowing on the upper surface. More common in humid areas and crowded plantings. Remove infected leaves; apply sulfur or copper fungicide. Space plants adequately for air circulation.
Geranium sawfly
Larvae (caterpillar-like, light green) defoliate hardy geraniums rapidly. Hand-pick larvae or apply spinosad-based insecticide per label. Most infestations are caught early when holes appear in leaves — inspect the undersides of leaves immediately.
Frequently asked
Why are my geranium leaves turning yellow?
For pelargoniums, the most common cause is overwatering. Check that soil drains freely and that containers have adequate drainage holes. If the soil is appropriately moist, yellowing lower leaves may simply be normal senescence as old leaves are shed. Per Clemson Extension HGIC, "too much water causes roots to rot and leaves to yellow." Nitrogen deficiency can also cause general yellowing — a light fertilizer application will confirm or rule this out within two weeks.
Why are my geraniums not blooming?
The most common reason: insufficient light. Pelargoniums need at least 5–6 hours of direct sun for strong bloom. The second most common reason: too much nitrogen fertilizer, which produces lush leaves and suppresses flowering. Cut back on nitrogen feeding and make sure the plant has adequate sun.
Can I bring my pelargoniums indoors for winter?
Yes. Move them before the first frost, pot them up in fresh potting mix if they were in ground beds, and place them in the brightest window available or under grow lights. They will go semi-dormant and look ragged through winter but should rebound with new growth as day length increases in late winter. Cut them back by half at this point to promote compact regrowth.
Are hardy geraniums and pelargoniums related?
They are in the same plant family (Geraniaceae) but are different genera. Per Missouri Botanical Garden, they were once classified together under Geranium but were split in the 18th century when their differences became evident. They cannot be hybridized, and their care requirements are substantially different.
How big do hardy geraniums get?
Most landscape cranesbills form mounds 12–24 inches tall and spread 18–30 inches wide over several years. 'Rozanne' is among the larger types, spreading 24–30 inches. Geranium sanguineum forms a tighter mound of 10–15 inches. Most cranesbills are well-behaved — they spread slowly and are not invasive in North American gardens.