At a glance
| Botanical name | Populus deltoides (eastern and plains cottonwood); also P. fremontii, P. angustifolia |
|---|---|
| Family | Salicaceae (willow family) |
| Native range | Eastern cottonwood: Alberta east to Quebec, south to Florida, Texas, Arizona and northern Mexico; Fremont and narrowleaf cottonwood: Southwest and Intermountain West |
| USDA zones | 3–9 (eastern cottonwood, per Morton Arboretum) |
| Mature height/spread | 75–100 ft tall, 50–75 ft wide (Morton Arboretum) |
| Growth rate | Very fast |
| Light | Full sun |
| Soil | Moist, well-drained to wet; best on moist sandy loams and silts |
| Wildlife value | High: raptor nest trees (eagles, hawks), woodpeckers and other cavity nesters, songbirds, mammals |
| Drawbacks | Cotton from female trees, brittle limbs, water-seeking roots, suckers, size |
What a cottonwood tree is
Cottonwoods are the large, fast-growing, streamside members of the poplar genus, Populus. The species most people mean is eastern cottonwood (Populus deltoides), which includes the eastern form and the plains cottonwood of the Great Plains (P. deltoides var. monilifera, also listed as var. occidentalis). In the West, Fremont cottonwood (P. fremontii) and narrowleaf cottonwood (P. angustifolia) fill the same streamside role. For how cottonwoods relate to aspens, balsam poplar and nursery hybrids, see the poplar tree guide.
The name comes from the seeds. Cottonwoods carry male and female flowers on separate trees, and in late spring or early summer female trees release huge numbers of tiny seeds wrapped in white, cottony hairs. The USDA Forest Service's Fire Effects Information System (FEIS) describes eastern cottonwood as a shade-intolerant pioneer that typically establishes on freshly exposed sandbars, streambanks and other floodplain sites, and notes that cottonwood stands depend on periodic flooding to regenerate. FEIS calls plains cottonwood the fastest-growing tree in the Great Plains.
How to identify a cottonwood tree
- Leaves: alternate, broadly ovate to triangular (the "deltoid" in deltoides), about 3 to 5 inches long and nearly as wide, pointed, square at the base and finely toothed or wavy along the edges, on slender, flattened stalks 2 to 3 inches long that make the leaves rattle in wind, per the Minnesota DNR.
- Buds: covered with chestnut-brown, resinous scales; they become sticky in late spring.
- Bark: light gray on young trees; on mature trunks thick, dark gray and deeply furrowed with wide, flat ridges (Minnesota DNR, FEIS).
- Form: a narrow, conical crown when young that becomes broad and open with maturity, supported by a massive trunk.
- Flowers and seed: dangling catkins in early spring before the leaves; in late spring or early summer, female capsules split open to release cotton.
- Fall color: yellow to yellowish orange.
| Tree | Leaf | Bark | Where |
|---|---|---|---|
| Eastern/plains cottonwood | Broadly ovate to triangular, finely toothed or wavy, flattened stalk | Thick, deeply furrowed, dark gray | East, Midwest, Great Plains |
| Fremont cottonwood | Triangular to kidney-shaped, rounded teeth, flattened stalk | Thick, gray, deeply furrowed with flat-topped ridges | Southwest stream corridors |
| Narrowleaf cottonwood | Narrow, lance-shaped; short stalk that is not flattened | Smooth, light yellow-green, later shallowly furrowed | Western Great Plains and Intermountain West |
| Quaking aspen (look-alike) | Small, nearly round, finely toothed | Smooth, creamy white to light green | Cool mountain and northern sites |
| Hybrid poplar (look-alike) | Often cottonwood-like | Variable | Planted rows and windbreaks |
Sources: Minnesota DNR, USDA Forest Service FEIS and Utah State University Extension (Fremont and narrowleaf cottonwood). For the aspen side of this comparison, see the aspen tree guide; for winter identification by trunk alone, see how to identify a tree by bark.
Types of cottonwood
Eastern cottonwood (Populus deltoides)
The big cottonwood of river bottoms, ranging from Alberta east to Quebec and south to Florida, Texas, Arizona and northern Mexico, per FEIS. The Morton Arboretum describes it as a very large, extremely fast-growing tree, about 75 to 100 feet tall and 50 to 75 feet wide at maturity, hardy in USDA zones 3 to 9. It is common along rivers, lakeshores and in wet, disturbed ground.
Plains cottonwood
The Great Plains form of P. deltoides. The Minnesota DNR describes it as found throughout Minnesota along rivers and in groves, very fast-growing and shade-intolerant, and extensively used in windbreaks. FEIS calls it the fastest-growing tree in the Great Plains and an especially important nest tree for raptors.
Fremont cottonwood (P. fremontii)
The cottonwood of low-elevation streams and river drainages throughout the Southwest. Utah State University Extension describes broadly triangular to kidney-shaped leaves with rounded teeth that turn bright gold in fall, calls it a good, large cottonwood for the right setting, and lists it for zones 5 to 9, with weak wood and a need for abundant water.
Narrowleaf cottonwood (P. angustifolia)
A stream-corridor species native from the western Great Plains through the Intermountain West, with narrow, lance-shaped leaves on short stalks that are not flattened, per Utah State University Extension, which calls it Utah's most common native cottonwood. It hybridizes with other cottonwoods; lanceleaf cottonwood (Populus × acuminata) is a common cross.
Cottonwood fluff: what it is and what it is not
Every late spring or early summer, female cottonwoods shed their seed in drifts of white fluff. Colorado State University Extension notes that cotton shed in June is often abundant enough to turn nearby lawns white, and Ohio State University's Buckeye Yard and Garden onLine warns that massive quantities can clog air conditioners, car radiators and swimming pool filters, and that the fiber is highly flammable around open flames. It also collects on window screens and in gutters.
Is cottonwood fluff an allergen? Colorado State University Extension says the cotton itself has no allergenic properties, and Ohio State reports no evidence that it triggers allergic reactions. People with symptoms during the June cotton release are probably reacting to wind-borne pollen from grasses, weeds or other trees. Cottonwood pollen, released by male trees in early spring (April in Colorado), is a separate matter: CSU notes it causes problems for allergy sufferers. For low-pollen planting ideas, see best plants for allergy sufferers.
Living with an existing female cottonwood
- Rinse air-conditioner condenser coils gently with a garden hose once the cotton release ends.
- Empty pool skimmer baskets daily during the release.
- Clean gutters after the release rather than before.
- Keep open flames away from drifts of cotton.
A young female tree may go years without cotton: CSU and Ohio State both note that seedlings take several years to mature enough to flower. CSU adds that ethephon is labeled to prevent cotton on female trees but must be applied while the flowers are developing.
Cottonless cottonwoods (male cultivars)
Because only female trees make cotton, nurseries propagate male clones and sell them as "cottonless" cottonwoods. The University of Minnesota's profile of 'Siouxland' describes it as a cottonless cottonwood introduced by South Dakota State University that is resistant to rusts, reaching about 70 to 80 feet tall and 40 feet wide. Ohio State's BYGL names 'Siouxland', 'Sparks' and the hybrid Populus × canadensis 'Robusta' as cottonless choices.
Keep three limits in mind. Colorado State University Extension warns that hybrids sold as "sterile female" clones are not cottonless: their seed is not viable, but they still produce plenty of cotton. A male cottonwood still sheds pollen in early spring, and some municipalities restrict male trees for that reason. And it still has every other cottonwood trait: huge size, brittle wood and water-seeking roots. Cottonless solves the fluff problem, not the siting problem.
Where cottonwoods belong
Cottonwoods are outstanding trees in the right place and expensive mistakes in the wrong one.
| Site | Fit | Why |
|---|---|---|
| River, creek or pond edges; floodplain restoration | Excellent | Native habitat; cottonwood stands depend on periodic flooding (FEIS) |
| Plains shelterbelts and large rural properties | Good | Fast shade and wind protection; Minnesota DNR notes extensive windbreak use |
| Large open park or acreage, well away from structures | Good (male cultivar) | Room for a 75–100 ft tree; no cotton |
| Suburban lot, near the house, pool, AC unit or sewer line | Poor | Limb failure risk, roots in pipes, cotton, sheer size |
For shelterbelt and windbreak options beyond cottonwood, see plants for windbreaks.
Roots, limbs and other siting risks
Roots
The Morton Arboretum notes that cottonwood roots are shallow, aggressive and can invade septic and sewer systems, and that the tree produces suckers. Like other poplar roots, they exploit leaking sewer and drain lines, and the University of Minnesota advises placing a cottonwood such as 'Siouxland' away from walkways and sidewalks. The root behavior and sewer-line guidance shared by all poplars are explained in the poplar tree guide; sources do not give a single safe planting distance, so locate sewer laterals, septic systems and foundations first and keep a cottonwood well clear of all of them.
Are cottonwood trees dangerous?
The real risk is above ground. The Morton Arboretum lists weak wood and branch structure and high susceptibility to ice damage, noting that its rapid growth makes it weak-wooded and brittle. Ohio State's BYGL adds that cottonwoods are notorious for dropping large branches and advises leaving the area during high winds. Large cottonwoods near homes, driveways, play areas or roads deserve periodic inspection by a certified arborist, particularly if you see dead limbs, cracks, cavities, fungal conks or included bark in narrow forks.
Litter
Expect catkins in spring, cotton in early summer from female trees, twigs and branches after storms, and a large leaf drop in fall.
Planting and care
- Choose a male cultivar for any site near people or equipment, and a native seedling or local cutting for restoration sites.
- Plant in full sun with reliable moisture. Cottonwoods are shade-intolerant and grow best where roots reach moist soil.
- Use dormant stock. Utah State University Extension notes that cottonwoods are easily propagated from cuttings 10 inches or longer taken from young branches in winter and planted in spring with about an inch showing above ground; the new tree is genetically identical to the parent.
- Protect from browse. Cage or wrap young stems on sites with heavy wildlife browsing.
- Train structure early, in winter. Keep a single strong leader and remove narrow, competing forks while they are small. The University of Minnesota notes 'Siouxland' needs annual pruning to hold its form and should be pruned in winter, since warm-weather pruning leaves it vulnerable to pests and diseases.
- Do not over-fertilize. Extra nitrogen pushes soft growth on a tree that already grows fast.
Pests and diseases
The University of Minnesota's 'Siouxland' profile lists the problems cottonwoods share: dieback, cankers, leaf spots and powdery mildew, plus borers, aphids, caterpillars and scale.
- Leaf rust: causes early leaf drop on susceptible trees; 'Siouxland' is listed as resistant to rusts. See how to identify rust diseases.
- Cankers and dieback: Cytospora and other canker fungi attack stressed and wounded trees; see tree cankers.
- Insects: borers, aphids, caterpillars and scale; aphid galls on leaf stalks are usually cosmetic (plant gall ID).
Wildlife and wood
Cottonwood stands are among the richest wildlife habitats on the Plains. FEIS calls plains cottonwoods a very important nesting substrate for raptors: golden and bald eagles, several hawk species, Lewis's and red-headed woodpeckers and other cavity nesters use them, and plains cottonwood bottomlands are the only natural habitat for fox squirrels. The Morton Arboretum lists value for mammals, sapsuckers and songbirds.
Is cottonwood a hardwood? Botanically yes: like all broadleaf trees, it is classed as a hardwood. In practice the Minnesota DNR describes the wood as soft and lightweight, warping easily and rotting readily; FEIS lists pallets, crates, paper pulp, fiberboard and some furniture among its uses.
Is cottonwood good firewood? Not very. Utah State University Extension's firewood table puts dry cottonwood at about 15.8 million BTU per cord, roughly 79% of green ash, and describes it as one of the lightest woods, with about half the heat by volume of Osage-orange. It splits easily, so it is usable for shoulder-season fires if split and seasoned thoroughly.
Common mistakes
| Mistake | Why it matters | Do this instead |
|---|---|---|
| Mistake | Why it matters | Do this instead |
| Buying an unspecified cottonwood seedling for a yard | An unsexed seedling may grow into a cotton-producing female, and "sterile female" hybrids still make cotton | Buy a named male clone such as 'Siouxland' |
| Planting near the house, pool, AC unit or sewer lateral | Cotton, roots and falling limbs all land on what you most want protected | Reserve cottonwoods for large open or streamside sites |
| Blaming the cotton for spring allergies | Grass and weed pollen fly at the same time; the cotton itself has no allergenic properties, per CSU Extension | Track grass pollen counts; plant low-pollen species |
| Ignoring dead limbs on a large cottonwood | Weak wood and heavy limbs fail in storms | Have large trees near targets inspected by an arborist |
| Letting narrow forks develop on young trees | Tight forks become weak unions as limbs grow heavy | Train to one leader early in late winter |
Frequently asked
What does a cottonwood tree look like?
A cottonwood is a very large tree with a massive trunk, thick, deeply furrowed gray bark and a broad, open crown of heavy limbs. Its leaves are broadly triangular, about 3 to 5 inches long, and hang on flattened stalks that make them rattle in wind. Female trees are easiest to spot in late spring or early summer, when they release drifts of white cotton.
Where are cottonwood trees found?
Eastern cottonwood grows along rivers, lakes and wet bottomlands from Alberta east to Quebec and south to Florida, Texas, Arizona and northern Mexico, including the Great Plains. Fremont cottonwood lines streams across the Southwest, and narrowleaf cottonwood follows stream corridors from the western Great Plains through the Intermountain West. All of them depend on moist soil near water.
When do cottonwood trees bloom?
Cottonwoods flower in early spring as dangling catkins, before the leaves open; Colorado State University Extension puts pollination in April there. The white cotton comes later, in late spring to early summer (late May or June in Minnesota, June in Colorado), when the female capsules split to release seed. Timing shifts with latitude and elevation.
Is cottonwood good firewood?
Cottonwood is a poor firewood. Utah State University Extension rates dry cottonwood at about 15.8 million BTU per cord, roughly 79% of green ash, and calls it one of the lightest woods. It splits easily; season it well and use it for mild-weather fires.
Is cottonwood a hardwood?
Yes, botanically. Cottonwood is a broadleaf, flowering tree, so its lumber is classed as hardwood, even though the wood itself is soft and lightweight. It is mostly used for pallets, crates, pulp and fiberboard.
Are cottonwood trees dangerous?
They can be near homes. Cottonwoods grow to 75 to 100 feet with weak, brittle wood; Ohio State notes they are notorious for dropping large branches, and the Morton Arboretum says their roots can invade septic and sewer systems. Mature cottonwoods near houses, driveways or play areas should be inspected periodically by a certified arborist.
Does cottonwood fluff cause allergies?
Generally no. Colorado State University Extension says the cotton has no allergenic properties, and Ohio State reports no evidence that it triggers allergies. Sneezing during the June cotton release is usually from grass, weed or tree pollen in the air at the same time, while cottonwood's own pollen comes earlier in spring.
Sources
- Populus deltoides, eastern cottonwood (Fire Effects Information System), USDA Forest Service
- Eastern cottonwood, Populus deltoides, The Morton Arboretum
- Cottonwood (Populus deltoides var. occidentalis), Minnesota Department of Natural Resources
- Cottonwood Cotton (PlantTalk 1758), Colorado State University Extension
- Cottonwoods are Living Up to Their Name in Ohio, The Ohio State University Buckeye Yard and Garden onLine
- Siouxland Poplar, Populus deltoides 'Siouxland', University of Minnesota
- Fremont Cottonwood, Utah State University Extension Forestry
- Narrowleaf Cottonwood, Utah State University Extension Forestry
- Wood Heating, Utah State University Extension Forestry