“Many gardeners have mixed feelings about this time of year,” says Doris Taylor, The Morton Arboretum’s plant information specialist. “They are sad to see another garden year draw to a close, while at the same time relieved to get a break from weeding, watering and more weeding. But, there are still a few more chores.”

Continue watering plants and trees until the ground is frozen, especially evergreens, because they don’t shut down like other plants do. “The soil moisture really fluctuated this year,” says Taylor, who manages the Arboretum’s Plant Clinic. “Even though we’ve had some really big rains, people have been reporting that their soil is quite dry.”

Decide if your trees and shrubs need a light pruning now or if they can wait until late winter. “If you need to take off one or two diseased or crossing branches, go ahead. You can also cut back limbs that are blocking a sidewalk or have overgrown their space. But don’t do a complete pruning job,” said Taylor. February and March are the best months to prune, when woody plants are dormant, so look for a future column on this topic.

Perennials can provide “winter interest” in the stark landscape. But whether you cut them back or not generally comes down to personal preference, said Taylor. She recommends not cutting back plants that have attractive seed heads that birds eat, such as coneflowers and Rudbeckia. Plants such as ornamental grasses or irises that have attractive seed pods are also worth keeping tall.

However, don’t cut back evergreen perennials such as alumroot, bishop’s cap, lavender, evergreen ferns and Christmas-rose. “You can remove brown leaves and give them a haircut, but don’t cut them all the way back,” said Taylor. “You want to protect the crown and give the plant some insulation from the cold.”

Other good housekeeping tasks:
1. Remove weeds and their seeds and discard any diseased or infected leaves in the trash can. Don’t compost them. Diseased leaves harbor spores that can re-infect new leaves next year. “This year we have a lot of fungal problems, powdery mildew, leaf spots and even spider mite problems,” said Taylor. “So the more you can eliminate diseased leaves, the better.”

2. When temperatures are consistently below freezing, usually after Thanksgiving, put down a 3-4 inch layer of winter mulch. (If you mulch too early, you may delay the soil from freezing.) While not necessary for all plants, winter mulching keeps soil moist and protects plants from winter freeze-thaw cycles. If not protected, some plants  can “frost heave” up out of the ground. Mulch can be composted leaves or Christmas tree boughs or wood chips.

Good plants to mulch include alumroot, lady’s mantle, lamb’s ears, ferns, small bulbs such as crocus and snow drops, newly planted perennials, shrubs and trees, as well as plants alongside sidewalks.

While these chores can be a bore, Taylor said to think of it this way: “The more time spent in tidying up the garden now means less work in spring.”

Glad You Asked
Q. I haven’t raked leaves yet. Can I just leave them?
A. Fallen leaves are “black gold,” said Taylor. They break down and nourish the soil. Mow over them a couple of times, rake them back on the beds as winter mulch.

Q. How low should I cut my ornamental grass?
A. The Arboretum Plant Clinic recommends at least 3-6 inches off the ground.

This post was adapated from an article written by The Morton Arboretum and first published in the Chicago Sun Times.

One of the best things we can do to promote this life is to mulch around our trees and shrubs. So what exactly lives down there? Everyone knows about earthworms that recycle the soil and tunnel through it. When you dig down, you can see other beneficial critters, such as cicadas and beetles. They shred dead plants, eat other organisms, burrow in the soil and stimulate microbial activity.

The microbes, which include bacteria, fungi, protozoa and nematodes, also play important roles in the food web, including suppressing diseases, making soil stick to itself and storing nutrients. While they are invisible to our eyes, their fascinating forms inspire science fiction creatures we see in movies, video games and comic books.

Mulching is one way to enrich urban soil. But the soils of our cities and towns have other problems, including compaction and water retention. The Morton Arboretum is leading the way in researching tree root development in urban soil. Dr. Gary Watson, Head of Research at the Arboretum, is one of the top researchers in the world in this field.

The Morton Arboretum is a conduit for this knowledge to reach landscapers, arborists and other professionals. As a result, professionals working on your home landscape, our parks and other urban spaces are using cutting edge methods. It’s one of the many ways the Arboretum serves as a resource for our community and makes the world greener, healthier and more beautiful.

Questions for you:

1. Whether you live in a new housing development, established town or center of a big city, urban soils are usually of poor quality. What do you do to nourish your soil? Share your experiences and best practices with us!

2. What do you do when you are digging in the soil and come across a worm, beetle or other critter? Which of these 4 types best describes you?

A. Screamer – they gross me out, but I leave them alone.
B. Squasher – they gross me out, and I kill them.
C. Scientist – they fascinate me, and I try to learn about them on the internet and books.
D. Nurturer – I do everything I can to help them thrive.