Description

White poplar is a tall deciduousa shrub or tree which sheds its leaves annually tree in the Willow family (Salicaceae) that may reach 70 feet or more in height and 2 feet in diameter. The smooth, greenish-white bark becomes dark and rough on older trees. Young green or brown twigs are coated with dense wooly hair, especially near the tip. A cross-section of the stem reveals a five-pointed, star-shaped pith. The 2 to 5-inch simple leaves are oval to maple-leaf in shape with 3-5 broad teeth or lobes, and are dark green above and covered with dense white hair below. Male and female flowers are borne in catkins on separate trees and appear sometime in March and April. The small seeds are adorned with cottony fluff. Mature trees produce thousands of wind-dispersed seeds that may be carried over long distances. It spreads primarily by vegetative means, through root suckers. Large numbers of suckers from a single tree can quickly develop into a dense colony.

Habitat

It favors full sun habitats such as fields, forest edges and wetland fringes. It is frequently found in old home sites from which it spreads into surrounding forest and field.

History and Introduction

White poplar was first introduced to North America in 1748 and has a long history in cultivation. It is chiefly planted as an ornamental for its attractive leaves of contrasting color (i.e., green above, white below). It has escaped and spread widely from many original planting sites. Because it is susceptible to a wide variety of pest insects and diseases, and is easily damaged by storms and wind, the ornamental value of white poplar is low.

Threats

This strong competitor grows in a variety of soils, produces large seed crops, and re-sprouts easily in response to damage. It escaped and spread from original planting sites to out-compete native tree and shrub species and interferes with the normal progress of natural community succession. Dense stands reduce the amount of sunlight, nutrients, water and space available for other plants.

Dispersal Methods

Local spread of white poplar is primarily by vegetative means, through root suckers. Root suckers arise from adventitious buds on the extensive lateral root system. Large numbers of suckers from a single tree can quickly develop into a dense colony. Suckering can occur naturally or as a result of damage or other disturbance to the parent plant. Mature white poplar trees produce thousands of wind-dispersed seeds that may be carried long distances. 

Control

White poplar can be controlled using a variety of physical and chemical controls. Removal of seedlings and young plants by hand will help prevent further spread or establishment. Plants should be pulled as soon as they are large enough to grasp. The entire root system, or as much of it as possible, should be removed to prevent resprout from fragments. Hand removal of plants is best achieved after a rain, when the soil is loose.

Trees of any size may be felled by cutting at ground level with power or manual saws. Because resprouts are common after cutting, this process may need to be repeated many times until the reserves of the tree are exhausted. Girdlingthe strangling of a tree branch or tree trunk by something wrapped around it, which chokes off the flow of nutrients, which kills the tree by severing tissues that conduct water and sugars, also may be effective for large trees, especially if accompanied by application of a systemic herbicide to the cut area. A hatchet or saw is used to make a cut through the bark encircling the base of the tree, approximately six inches above the ground and deep into the bark. Girdling will kill the parent tree but may require follow-up cutting or treatment of sprouts with an herbicide. 

Chemical control of white poplar seedlings and small trees has been achieved by applying a 2% solution of glyphosatea widely used herbicide that can kill certain weeds and grasses, it works by blocking an enzyme essential for plant growth (e.g., Roundup®) or triclopyrherbicide used to control both broadleaf and woody plants (e.g., Garlon® 3) and water plus a 0.5% non-ionic surfactant to the foliage until the leaves are thoroughly wet. Use of low pressure and a coarse spray with large droplet size will reduce spray drift and damage to non-target plants.