Beware the buckthorn; spot it this fall

Buckthorn is a small tree or large shrub that is an invasive plant and a common weed in Chicago-area gardens. It is easy to spot in fall because it tends to hold its green leaves later than other deciduous trees and shrubs.

Cut buckthorn trees at ground level and quickly treat the stumps with a systemic herbicide to kill the root system. Smaller trees can be dug out with a sharp spade.

Shredded leaves make good mulch for your garden beds. A serious gardener may want to rent a shredder, but be forewarned that they are very noisy so it is best to use ear and eye protection. Although using a shredder results in finer leaf mulch, it is a time-consuming process. For the average gardener, a lawn mower with a bag to catch the leaves will be adequate. The mower does not cut the leaves up as finely as a shredder but works a lot faster.

In addition to their usefulness as mulch, ground-up leaves also will decompose more quickly than whole leaves in a compost pile. Shredded leaf mulch also can be purchased from some garden centers.

Mulch any new perennials planted this year and especially those installed in late summer or fall. The freeze-and-thaw cycles in spring can push newly planted perennials out of the ground. Established perennial borders generally do not need to be mulched. You can simply leave a light layer of leaves in the bed to provide some winter protection. Leave the dried tops of perennials standing for winter interest; you can cut them back later when they start looking bad.

Continue cutting your grass throughout the fall as needed. Make your last cut of the year at a lower height of 2 inches. Take care to stay off the lawn when it is covered with frost. Cold weather will eventually stop the growth of the grass.

• Tim Johnson is director of horticulture at Chicago Botanic Garden, chicagobotanic.org.