Many landscapes are strongly suggesting that fall is here and the perennials have decided to pack up and call it a growing season. Some perennials cast off dried leaves and spent seedpods – leaving our garden’s looking more like a compost pile than a flowerbed.
First you need to know that each perennial plant is different, some should be cut off at ground level, some not cut at all, and others should be cut some and then cut more in early spring.
Most perennials are the herbaceous kind – they die back to the ground every year. Herbaceous perennials are daylilies, hosta, and astilbes. These you want to prune the dead leaves and stems back to the ground and tuck them into their beds with a layer of mulch. As a general rule of thumb, mulch shade perennials more and sun-loving perennials less, as the sun perennials are more prone to root rot. The mulch layer will also keep the root system from drying out during the winter.
The semi-herbaceous plants are Black-eyed Susan’s and Shasta daisies. These perennials shoot up long flowering stems that die back after blooming but the crowns of basal leaves at the bottom of the plant are evergreen. To winterize these plants, cut back the dead and dying flower stalks and leave the green leaves. The plants use these leaves to photosynthesize throughout the winter and they add some much needed color to the winter garden.
The last group of perennials is the evergreen and subshrub perennials. Some evergreen perennials are candytuft and moss phlox, and some subshrubs are plants like butterfly bush, Russian sage, and artemesias. The only pruning you want to do to these plants in fall is the removal of dead plant material and leggy growth from evergreen perennials. You do not need to prune the subshrubs – doing so can be harmful to the plant.
Other perennials you might want to consider leaving alone are plants that provide structural interest or seeds for birds. We leave the ornamental grass to provide interest, and perennial like purple coneflower and sunflower provide food for birds through the winter. Goldfinches will gladly gobble up any seeds from these plants. Leaving these perennials alone will be much more rewarding than cutting them back to the ground. I’ve been told by some readers, they like the ornamental grasses cut for winter – it’s up to you – we’re protecting the birds.
Raking the leaves – the answer to whether or not to rake the leaves depends primarily on the type of turf. In lawns of fine-bladed grass such as fescue, fallen leaves can mat down to the point where they smother the grass and prevent newly sown seeds from germinating, so it’s good to rake the leaves routinely. Be gentle as you rake, and use a plastic or bamboo rake rather than a metal one to avoid ripping the tender blades of grass out of the ground.
If neat is your thing but you’d rather not rake, consider using a mulching mower. Shredded leaves are a wonderful source of organic matter; they will decompose and enrich your soil in ways that no “store-bought” product can.
If you would rather not rake or mow, then blow the leaves. Leaves blown into nearby beds can serves as protective winter mulch and in time they too will decompose to enrich the soil. Just make sure you don’t smother the crowns of plants or they may rot during the cold, wet winter.
You can also let the leaves fall naturally in the garden beds, but it’s good to move them periodically from around the crown of plants. Some gardeners prefer to rake or blow leaves into a large pile, sprinkle the pile with a few cups of blood meal and wait a few months for the leaves to rot; the following spring you are left with a particular kind of compost called leaf mold, a great amendment for anything that grows.
There’s still a little bit more to do in the gardens –get out and enjoy the beauty of fall!
