Poplar trees (Populus species) are fast-growing deciduous trees. This group includes cottonwoods and aspens. Hybrid and tulip poplars are particularly desirable with home gardeners for their beauty and shade-casting abilities. Commercial growers often grow hybrid poplars because they can harvest the wood in about five to seven years. The size and appearance of these trees vary by species and cultivar but, in general, their basic care requirements are the same.
Poplar trees tend to grow best in climates with mild winters and warm summers. Most thrive in United States Department of Agriculture (USDA) growing zones 4 through 9. Populus tremuloides, or the quaking aspen, one of the most widespread poplars in America, is cold-hardy all the way to USDA zone 1, according to the University of Connecticut. The common P. nigra, or the Lombardy or black poplar, is hardy to USDA zone 4.
Soil and Water
All poplar trees thrive in wet soils. These trees are not drought-tolerant, according to North Dakota State University, and need regular watering. They are often found growing along riverbanks and streams, or in areas where flooding is common. If you have an area of your landscape that frequently collects standing water, then that would be a good place to plant a poplar. While these trees can tolerate almost any type of soil, from sandy to clay, the soil does need to be continually moist.
Light and Location
Poplars need full sun, according to the University of Connecticut. These trees grow quite large--some species grow to 100 feet in the wild--and are not usually found in the understory of the forest. Instead, they tower over their counterparts. Plant these trees in full sunlight, but not under anything such as power lines. In addition, the roots are very disruptive, so do not plant a poplar next to a sidewalk or sewer lines.
Poplar trees grow with very little care, but that fast growth comes with a price. The wood is very weak and prone to splitting. A windstorm may bring down branches or even split the tree in half. Take care to maintain your tree. Prune off tight angles so the wind can go through the tree. Make sure broken or diseased branches are removed often. Suckers (branches that grow from the roots) are also a problem with this tree, according to North Dakota State University, and should be removed.
There are five fungi that can affect poplar trees, according to Colorado State University. These fungi travel on water and are particularly bad during wet, cool springs. Fungal infections usually affect the leaves of the poplar tree, causing them to develop unsightly spots, holes, or even drop prematurely from the tree. Fungi can also enter the tree's wood, killing the wood and causing cankers to form. Treat your poplar with a systematic fungicide in the spring to prevent such infections, and prune off any branches that have cankers (dark, sunken areas of cracked wood). Remove fallen leaves that have been infected, as the fungi can overwinter in the soil.