Populus

( PAW - pew - luss )

At-A-Glance Information

This genus of deciduous trees, commonly called Poplar, Cottonwood, or Aspen, includes species which need full sun and regular water to perform well in the landscape. The flowers will attract butterflies and other pollinators to the garden. These are fast-growing, hardy trees that are best suited to rural areas which experience hot summers and cool winters. Many species have great fall color and green leaves are triangular and toothed. Catkins appear in springtime before leafout in springtime. Female trees produce fluffy, cottony seeds that can make a mess in hardscaped areas. Use these trees for quick visual effect, as windbreaks, or for erosion control in sloped areas. Take care when planting these trees in the landscape, as some species have plant parts that are toxic to animals if ingested.

populus Species and Varietals

The genus Populus is a member of the plant family Salicaceae and includes between 25 and 30 species. The trees in this genus are closely related to those in Salix (Willow) and Xylosma (Brushholly). Populus Tree growing zones vary depending on the species. For more information, see the descriptions below. To find your zone, click here: Zone Map.

Populus x acuminata (Populus acuminata) (Lance-Leaf Cottonwood, Lance-Leaf Poplar)
This species is a hybrid of Populus angustifolia and Populus deltoides; it does well in USDA hardiness zones 3-9 or Sunset growing zones 1-11 and 14-21 and reaches 40-60 feet tall and 35-45 feet wide when mature. Leaves are glossy and dark green above, pale green underneath, and turn yellow in autumn. This is a seedless species, and is native to the Rocky Mountains of North America. Cultivar 'Highland' (also called Highland Poplar)
has a upright habit and is seedless, with a good resistance to pests and diseases.

Populus adenopoda (Chinese Aspen)
This species is native to subtropical regions in Asia, and reach a maximum height of 100 feet tall. Trees are cultivated in their native range for timber used for building construction and furniture production. Chinese Aspen trees are suited for USDA hardiness zones 5-10.

Populus alba (White Poplar, Silverleaf Poplar, Silver Poplar, Abele, Silver-White Poplar, Yin Bai Yang, 银白杨)
This species does well in USDA hardiness zones 3-9 or Sunset growing zones A3, 1-11 and 14-21, and is native to Europe and Asia. These trees top out around 40-70 feet tall and wide. Leaves are beautiful, and flutter in the breeze, revealing white undersides (hence the common name). This species produces a lot of suckers; a good quality if planted as a windbreak. Cultivars include 'Raket' (cone-shaped to 15 feet tall), and Populus alba pyramidalis (commonly called Bolleana Poplar, with a columnar shape and white or light grey trunk). This species is considered highly invasive across much of the United States, Argentina, Chile and Uruguay.

Populus angustifolia (Narrowleaf Poplar, Narrowleaf Cottonwood, Mountain Cottonwood, Willow-Leaved Poplar)
This species does well in USDA hardiness zones 3-7 or Sunset growing zones 1-11 and 14-21 and is native from Alberta, Canada down to Mexico (mostly in the Rocky Mountains at around 8,000 feet of elevation). These trees reach 50-60 feet tall and 35-45 feet wide, with narrow, willow-like leaves and green bark when young.

Populus balsamifera (Balsam Poplar, Bam, Bamtree, Eastern Balsam-Poplar, Hackmatack, Tecamahac Poplar, Tacamahaca, Balm of Gilead, Hackmatack, Heartleaf Balsam Poplar, Ontario Poplar)
This species does well in USDA hardiness zones 1-6 or Sunset growing zones A2, A3, 1-9 and 14-24 and is native from to the northern areas of North America (mostly in Canada and Alaska). This species reaches between 30-100 feet tall and 25-30 feet wide, with furrowed dark gray bark. Wood is brittle; protect from strong winds. Leaves are deep green on top and silvery underneath. Gold-yellow fall color.

Populus x canadensis (Canadian Poplar, Carolina Poplar)
This naturally occurring hybrid is a cross between Populus nigra and Populus deltoides, and is a vigorous grower. They do well in USDA hardiness zones 4-9, are broadly columnar and reach up to 130 feet tall when mature. Commonly grown cultivars include 'Robusta' and 'Aurea' (also called Golden Poplar or Golden Carolina Poplar). Canadian Poplar is considered invasive in Sough Africa, Europe, and North America.

Poplar x canescens (Grey Poplar, Abele, Silver Poplar, Silverleaf Poplar, White Poplar)
This species is a natural hybrid between White Poplar (Populus alba) and Common Aspen (Populus tremula). It is capable of reaching up to 130 feet tall with a trunk diameter of over 5 feet. Most trees in cultivation from this species are male, and grow well in USDA hardiness zones 3-8. This species is considered invasive in regions of South Africa and North America.

Populus ciliata (Himalayan Poplar, Pahari Pipal, Himalayan Balsam Poplar, Ban Peepal, Chalu, Biaon, Bhote Pipal, Bangikat)
These large deciduous trees have tall, straight trunks and are native to the Himalayan region in Asia. It is widely used in landscapes as an erosion-control and agroforestry tree, as it easily establishes in shallow soils, has a fast growth rate, and produces strong lateral roots. Crown is widely rounded. Himalayan Poplar grows well in USDA hardiness zone 6.

Poplar deltoides (Eastern Cottonwood, Necklace Poplar, Plains Cottonwood)
This species is native to southern Canada, eastern, central and southwestern United States, and northeastern Mexico. These large trees reach between 65 and 100 feet tall when mature, making them one of the largest North American trees. Bark is silver-white on young trees and turns dark grey and deeply fissured with age. This species grows well in USDA hardiness zones 2-9.

Populus euphratica (Euphrates Poplar, Desert Poplar, Diversiform-Leaved Poplar, Indian Poplar, Bahan, Bhan)
This species of Poplar is native to North Africa, the Middle East, Central Asia, and western China, where it grows in mixed temperate broadleaf forests and subtropical forests in dense thickets. Trees are commonly used as windbreaks, to control erosion, and for forestation programs in desert areas. This species grows well in USDA hardiness zones 9-11.

Populus fremontii (Western Cottonwood, Fremont Cottonwood, Alamo Cottonwood)
Best in USDA hardiness zones 4-9 or Sunset growing zones 1-12 and 14-21, this species is native to California and Mexico. It reaches 40-60 feet tall and 30 feet wide. Foliage is yellow-green and turns lemon yellow in cooler temperatures. Leaves last almost through the winter in mild climates. Cultivar 'Nevada' is a handsome seedless variety.

Populus grandidentata (Large-Tooth Aspen, Big-Tooth Aspen, American Aspen, Canadian Poplar, White Poplar, Big-Toothed Poplar, Popple)
This medium-sized tree species is native to eastern areas of North America, and typically reaches between 60 and 80 feet tall. Bark is thin and olive-green on younger trees, maturing to gray, thick grooved bark at maturity. Large-Tooth Aspen grow well in USDA hardiness zones 2-6.

Populus heterophylla (Swamp Poplar, Downy Poplar, Swamp Cottonwood, River Cottonwood)
These large deciduous trees are native to temperate regions of eastern North America and reach between 50 and 100 feet tall at maturity. Leaves are medium to deep green on their upper surface and pale green on their lower surface. The roots of these trees can take more water than other native poplars in their range. Best in USDA hardiness zones 5-9.

Populus lasiocarpa (Chinese Necklace Poplar, Heart-Leaf Poplar, Chinese Poplar)
This species is native to the humid forests in China, and is closely related to Wilson's Poplar (Populus wilsonii). It is suited for growing in USDA hardiness zones 6a-9b (minimum temperatures between -10 and 30 degrees Fahrenheit). These trees produce large leaves with hairy undersides. Flowers bloom from March through May, and fruits ripen from May to June.

Populus nigra (Lombardy Poplar, Black Poplar, Italian Poplar)
This species is best in USDA hardiness zones 2-10 or Sunset growing zones A3, 1-11, 14-24 and is native to Europe. It is great along driveways, as a windbreak, or for dry, cold, interior climates. Leaves are bright green and turn gold in fall. Suckers profusely in the garden. 'Italica' (pictured) is seedless and reaches 40-100 feet tall and 15-30 feet wide with upright branches. This species is considered invasive in North America (particularly in the Great Lakes region and Michigan), South Africa, Argentina, and Australia.

Populus tremula (European Aspen, Aspen, Common Aspen, Eurasian Aspen, Quaking Aspen)
This species is native to Africa, Asia, and Europe, and has dainty, glossy green leaves and grey-green bark. It is suited for USDA hardiness zones 2-6, and can be grown as a single-trunked or multi-trunked tree. Cultivar 'Erecta' (also called Swedish Columnar Aspen), is a narrow selection with great red fall color.

Populus tremuloides (Quaking Aspen, Trembling Aspen, American Aspen, Mountain Aspen, Golden Aspen, Trembling Poplar, Popple, Quakies)
Grows well in USDA hardiness zones 1-7 or Sunset growing zones A1-A3, 1-7 and 14-19 and is native to mountainous areas of the western United States (up to 9,000 feet in elevation). Short-lived and performs poorly in lowland regions. Smooth, pale bark and glossy green leaves. Reaches 20-60 feet tall and 15-20 feet wide at maturity, making a good background tree for wild-looking gardens and landscaped mountain properties. Commonly grown cultivars include 'Mountain Sentinel' (narrow, upright to 35 feet tall and 8 feet wide at 30 years), and 'Prairie Gold' (40 feet tall and 15 feet wide, bred to tolerate lowland conditions and resist common diseases).

Populus trichocarpa (Black Cottonwood, Western Balsam-Poplar, California Poplar)
This species is native to western North America, and is commonly used as a timber tree. Individuals reach between 98 and 165 feet tall. Bark is grey and quite hard. These trees are valued for their fast growth and scented foliage in springtime. Roots are invasive, and can cause damage to nearby foundations and hardscaped areas. California Poplar grows well in USDA hardiness zones 4-9 or Sunset growing zones 1-9 and 14-24.

Caring for Populus

Take care when planting these trees in the landscape, as some species have plant parts that are toxic to animals if ingested. The trees in this genus are somewhat famous for their aggressive root systems and suckering nature, and it is recommended to plant them at least 100 feet away from foundations, hardscaped areas, gas lines, septic tanks, and other utility lines. Before planting Poplars in the landscape, consider installing a 24-36 inch deep root barrier around the planting area, leaving 1-2 inches of barrier above the soil to prevent roots from travelling where they are unwanted. Also, consider purchasing a seedless male tree to prevent unwanted seedlings from popping up all over the garden. The best time to plant Poplar trees is in springtime once soil can be worked. They should be installed in full sun to partial shade. They will perform, grow, and flower better when situated in a spot that receives full sun (at least 6 hours each day). These trees are tolerant of a wide range of soils, from clay to loam to sand. They do not like disturbed or poor soils, and have issues with intense temperature and water fluctuations. Apply a thick layer of mulch around the base of trees to suppress weed growth, increase soil moisture retention, and help to regulate soil temperatures.

Newly planted trees should be watered regularly (about 10 gallons once a week) in their first year or so in the ground. At maturity, some species can tolerate dry spells, but they typically will perform better if provided with regular deep irrigations. Fertilize yearly in early springtime with an application of 2 inches of compost around the base of plants. Pull mulch back before applying, work the compost gently into the soil a bit, water it in, and then replace mulch. The best time to prune these trees is in late winter or early springtime. Remove dead, damaged, diseased, or crossing branches and lightly shape if necessary. These are considered to be weak-wooded trees, and will often drop branches or entire limbs during strong storms. Many will freely re-seed in the garden, and volunteer saplings should be pulled up on a regular basis. These trees have an average life expectancy of between 30 and 50 years before needing to be replaced in the garden, but can live for hundreds of years in their natural environments. Most species will re-seed freely in the garden (if they are not seedless cultivars), providing plenty of volunteer saplings that can be dug up and transplanted elsewhere.

Propagation

Poplar trees can be propagated either by using cuttings or from seed. To ensure that your propagated plant will have the exact same qualities and characteristics as the parent plant, use the cutting method. If you would like to experiment and see what plant you can grow from seed, just keep in mind that it will not necessarily be the same as the parent plant. To propagate your Aspen tree, follow the instructions below:

Propagating Poplar by Cutting

Gather your materials. You'll need a clean, sanitized, sharp pair of garden shears, rooting hormone, a pencil, and a 3-inch pot filled with well-draining compost or other organic material. A good substrate for propagation of cuttings is a light blend of 1/3 pasteurized soil or compost, 1/3 sand, vermiculite or perlite, and 1/3 coconut coir or peat moss.
In spring or early summertime, choose the plant that you'd like to propagate. Ensure that this plant has had a good watering the night before, as this will improve the chances your cutting will take root. Cut one or more 6 inch portion(s) of the end of a non-blooming branch and strip the leaves off of the lower half. Make a hole in your planting medium by pushing your pencil into the soil. Dip the end of the stem in rooting hormone, and plant it in your pot. Fill in soil around the cutting to support it, but do not pack it down too much.
Moisten with water, and ensure that the pot has good drainage. Your pot should be kept in warm, sunny conditions indoors (and not in direct sunlight). Water whenever your soil is dry under the top layer. After about four to six weeks have passed, your cutting should be rooted. When you notice new growth, you'll know you have roots.
Keep your new plant in an area with bright light (though not direct sunlight) and temperatures between 55 and 70 degrees Fahrenheit. Ensure that the soil stays moist, but not wet, until the next spring, when you can transplant it to its new home. Ensure that the last frost of the year has occurred before doing this, as it can seriously damage your new shrub.

Propagating Poplar by Seed

Keep in mind that the plant you get from seed will not necessarily mimic all of the characteristics of the parent plant. To propagate by seed, you will need a paper bag, a pot or tray filled with well-draining compost or other organic material, a spray bottle and a fork. The best potting medium for seed germination is a light blend of 1/3 pasteurized soil or compost, 1/3 sand, vermiculite or perlite, and 1/3 coconut coir or peat moss.
Water your prepared seed tray or pot filled with soil, and ensure that good drainage is occurring. Place your seeds in your prepared pot or seed tray about a quarter inch to a half-inch under the soil surface. Cover them with soil and water with your spray bottle. Place your tray of seeds in a warm area that receives bright, indirect light. A greenhouse is the most ideal climate, but a planting tray inside a window will do as well. Germination usually takes 7-14 days from sowing. Once you begin to see seedlings sprout and they are able to be handled, transplant them to their own individual 3-inch pots, filled with the same potting medium as described in Step 1. Loosen the seedlings from the potting medium by digging down with the tines of your fork about an inch and a half, gently working the seedling up until it is out. Then, replant the seedling in its individual pot.
Keep the seedling's potting medium moist, but not wet, by spraying the soil with your spray bottle. Keep your new plant in an area with bright light (though not direct sunlight) and temperatures between 55 and 70 degrees Fahrenheit. Ensure that the soil stays moist, but not wet, until the next spring (after the danger of frost has passed), when you can transplant it to its new home.

Poplar trees produce male and female (pictured above) flowers on separate trees.

Poplar seeds are flat and have wings, allowing them to travel through the air away from the parent tree.

Problems and Pests

Certain Poplar species are considered invasive in some regions; see the species descriptions above for more information. Check with local authorities before planting. These trees also have the tendency to produce many seedlings, which can quickly become a nuisance in the landscape if not hand-pulled frequently. Poplar trees are susceptible to developing issues with the following pests and diseases: