Ragged-looking perennials? Here’s what to do.

Ragged-looking perennials?  Here’s what to do.

Some of the perennials bordering my garden are starting to look a little tough. I was wondering if I should cut it now or wait until later this fall or even spring? I want to do what’s best for the plants.

– Jason Kim, Evanston

My goal at home is to leave as many perennials as possible, so there is interest in the garden in the winter. I avoid cutting perennials in my home garden because they look bad. When a plant looks bad is subjective, depending on each gardener’s point of view and his or her garden goals. Leaving perennials with leaf litter in the beds provides shelter for overwintering pollinators. I generally don’t cut back any of the perennials in my garden in the fall, leaving the natural look I prefer. Hostas can have good fall color but will eventually collapse and settle to the ground in late fall. Since they won’t have any interest in the winter, just cut them back as soon as they break down. Goldfinches will visit the seed heads of coneflowers, so cutting or cutting them off removes a food source for the birds.

Whether you cut back your perennials later this fall depends more on how you like your garden to look over the winter than on the health of your plants. Some gardeners prefer a clean look with all plants cut back and a light layer of mulch over the beds. Established perennials do not need to be covered for the winter. If you decide to reduce the perennials in your beds and mulch your home, it is best to use a very light layer of mulch of an inch or less. Since I don’t cut my perennial borders in the fall, some of the leaves burst into the borders and provide a light layer of mulch for the beds. I prefer this natural look for my garden. Perennials are then cut in the spring before they begin to grow. If you’re late with spring cleaning, be careful while trimming perennials so as not to damage any new growth that may have started. Cutting back perennials to a height of 6 to 8 inches in the spring instead of at ground level will help support and encourage pollinators in your garden.

If you install any new perennials this year, they should be covered for the winter to avoid frost accumulation in the spring. Mulch around plants, but don’t bury the crowns. Freezing and thawing of soil in the spring can push small, newly installed plants such as perennials grown in 1-gallon containers out of the ground. Covering new perennials installed in the fall also gives them more time to develop roots and become established before winter arrives.

For more tips on plants, contact the Chicago Botanic Garden’s Plant Information Service at plantinfo@chicagobotanic.org. Tim Johnson is Senior Director of Horticulture at the Chicago Botanic Garden.

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