By Bonnie Kirn Donahue
Extension Master Gardener
University of Vermont
Did you run out of time to cut back your perennial garden in the fall? You are not alone. In the past, I have also neglected to cut my perennials back, but this year I left them in place on purpose.
Leaving strong-structured perennials up over the winter can provide many benefits. The plant structure can add a wonderful sculptural element to the winter landscape, and the seed heads can provide food for winter birds.
This year, I experimented with purple coneflower (Echinacea purpurea), 'Goldsturm' black-eyed Susan (Rudbeckia fulgida 'Goldsturm'), globe thistle (Echinops ritro) and even common sunflowers (Helianthus spp.)
The key in northern New England is to pick plants that will hold up against snow. Even the strongest perennial may not be a match for a hard winter or heavy snow, but it might be worth a chance.
Deciding to leave your plants up over the winter can be great, but it gets complicated when trying to stagger spring maintenance with new growth in the garden.
Cutting back plants in the spring can be more difficult when they are moist, so let your plants and soil dry out a bit before attempting to cut them back. Taking the time to sharpen your hand clippers also will make this process easier.
If you have spring bulbs planted in the same bed, be gentle when cleaning up. Wait until after your bulbs have finished blooming.
An alternative to consider for next year is to cut down your perennials just before the ground begins to thaw. Cutting down last season's plants before your bulbs emerge will provide a clearer view of the new growth, and be more aesthetically pleasing.
After you relish the joy that comes with spring bulbs, deadhead the spent flowers before they go to seed, but resist the temptation to cut back the leaves until they fully dry out. As the leaves dry, the plant will send all of its energy back into the bulb and result in better flowers next year.
Cut back herbaceous perennials as close as you can to the ground. About 2-3 inches is fine. Woody perennials should be cut back by about a third. Ornamental grasses can be cut back to 6-12 inches.
Make sure to remove dead and decaying plant matter from your garden. While it can add organic matter and insect habitat to your garden if left, you need to balance this with the potential of spreading diseases from one year to the next.
Consider composting it instead unless the plant material is diseased. In that case, dispose of it away from the garden.
Mulching early on in the season will pay off for the rest of the year. Choose a natural garden mulch, such as shredded bark mulch, adding 2-3 inches of mulch throughout the garden. This amount may seem like a lot, but it will provide many benefits for you when done correctly, including weed suppression and moisture retention.
Make sure you clear a ring in the mulch around your plants, leaving room for the base of the plant to be open to the air. This will make your plants less susceptible to disease.
Next season intentionally leave up some of your perennial plants. See what does well, and what does not. With careful planning and staggering your spring clean-up, you can extend the season of your perennial gardens, from spring to spring.