Populus angustifolia aka Narrowleaf Cottonwood

Populus angustifolia is a tree in the willow family. It sheds its leaves each year. People call it narrowleaf cottonwood or Rocky Mountain poplar. Its home range runs from western Canada to northern Mexico. It grows across much of the Rocky Mountain region. Wild trees line streams in mountains, foothills, and dry plains. They also grow on sand bars with water close by.

In gardens, trees reach about 50–65 feet (15–20 metres) tall. One source gives a top height of 98 feet (30 metres). The slim crown forms a narrow cone. Its branches point up. Young bark feels smooth. It looks pale grey, whitish, or yellow-green. Older trunks have dark bark, deep grooves, and broad ridges. Shiny yellow-brown twigs have orange pores called lenticels. Long, curved buds hold resin and give off a scent. New leaves and buds smell sweet as they open in spring.

The narrow leaves look much like those of a willow. Each leaf grows alone. Leaves grow in turn on each side of the branch. Fine teeth line their edges, and their tips taper. Leaves look green on top and paler beneath. Resin can leave orange marks on their lower sides. Male and female flowers grow on separate trees. Pale yellow-green flower clusters, called catkins, hang from branches. They form in spring before the leaves open. Wind carries pollen; seeds need trees of both sexes. Small, dry seed cases called capsules split when ripe. Each splits into two parts. They hold many tiny seeds with cotton-like hairs.

This tree grows fast and needs a bright site. It needs soil that stays moist. Oregon State says it cannot cope with drought. Plants For A Future favours deep, rich soil that drains well. It accepts sand, loam, and clay, even heavy clay. Soil can be mildly acid, neutral, or mildly alkaline. Poor acid soil and thin dry soil slow growth. So does ground that stays waterlogged. It dislikes exposed upland sites and nearby plants that compete. Reported USDA hardiness spans zones 3–7. Wild trees may have short lives, though they grow fast.

Its roots help hold soil on banks and slopes. Yet its forceful roots can enter and damage drains. People have used young shoots to make baskets and rooting extracts. The weak, soft wood has local uses for posts and fuel. Recorded food uses include inner bark and buds chewed as gum. People also gathered aphid honeydew from beneath leaves to sweeten food. They used bark and fruit in folk remedies. The bark contains salicin. Plants For A Future lists no known hazards.