Green leaves in fall? Check for invasive buckthorn

Buckthorn is an invasive tree and a common weed in the Chicago region’s gardens and native habitats. It tends to hold green leaves later than other deciduous trees and shrubs in fall, so it’s easy to spot this time of year. Cut buckthorn at ground level and quickly treat the stump with an herbicide to kill the root system. Smaller trees can be dug out with a sharp spade.

Fallen leaves benefit garden beds

Now is also the time to repurpose fallen leaves — shredded leaves make good mulch for your garden beds.

For serious gardeners, you can rent a shredder, but they’re noisy and slow to use, so you’ll want to use ear and eye protection when shredding the leaves. Using a shredder is a time-consuming process, but it results in finer leaf mulch.

For the average gardener, though, a lawn mower with a bag to catch the leaves will do the job. A mower doesn’t cut the leaves up as finely as a shredder, but it works a lot faster. Ground-up leaves will also decompose more quickly if you’re using them in a compost pile. Shredded leaf mulch can also be purchased from garden centers. It’s also OK to simply let leaves naturally blow into your borders for mulch without shredding them.

You don’t have to add mulch to established perennial and shrub borders. I like to leave perennials up for winter interest, and I leave a light layer of leaves in the bed to provide some winter protection and save time on garden maintenance. Leaving leaves in garden beds for the winter also supports pollinators.

Cut back perennials when they start looking bad if you want to neaten up your garden. Any perennial plants you installed this year, especially anything you planted in late summer or fall, should be mulched for winter since the freeze-and-thaw cycles in spring can push newly planted perennials out of the ground.

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