As we approach winter, we wanted to touch on some general thoughts about how to prepare your perennial plants for winter.
In a broad sense, a perennial is a plant that blooms over spring and summer and lives for two or more years. Many of these go dormant over the winter, losing their leaves, but there are also some that maintain a semi-evergreen foliage status.
Since we can’t lump all perennials into one category, we can’t say one fall/winter care program works for everything you might have in your garden. It’s important to understand the plant you have and how to care for it so you can enjoy it year after year.
Here’s a quick guide to how fall/winter care might differ depending upon what’s in your garden.
These plants, like the coral bells and lungwort pictured below, maintain all or most of their foliage over Wisconsin’s winter season. These do not require any cutback in the fall, but will need to have their dead leaves removed in spring.
The periwinkle pictured below is a ground cover plant and generally will only need a trim during the growing season if it wanders outside of its space.
These plants shed their foliage in the fall and can be cutback to their base after they’ve gone dormant. In some cases, their stalks with seed heads can be left standing for birds to feed on, but you will want to remove any leaf debris that has collected around the plant’s base. Cleaning up the leaf debris will aid the plant by reducing the possibility of rodents using the material as bedding as well as reduce the chance that plant diseases will form which will affect the health of the perennial in the spring.
Here are some examples of deciduous perennials:
We’re highlighting grasses here because they are a common perennial in gardens. The dried portion of the stalk can typically be cutback in the spring leaving the new flush of green growth at the plant’s base to thrive.
Leaving perennial grass up throughout the winter season not only provides food for the birds, as they will enjoy the seed heads, but will also insulate the plant during winter and provide winter interest in a dormant garden.
Here are some examples of perennial grasses:
The last type of perennial we want to highlight here is from the woody perennial family. It is both the hydrangea and lilac shrubs. The reason we picked these two is because we wanted to talk about what it means to bloom on “old wood” vs “new wood”.
Old wood means exactly as it sounds. Blooms are created on the wood that was grown the previous season. Any removal of the “old stems” will alter the blooms for the following year. Best time to trim these plants is after they flower and before the fall to give the stems a chance to make next year’s flower.
In contrast, new wood means that blossoms will emerge from new growth. This means the plant can be cutback in dormancy without compromising next year’s flower.
It can get a little tricky with hydrangea as this family of shrubs has varieties that bloom on one or the other type of wood.
The Annabelle Hydrangea blooms on new wood, so there will be no harm done if pruned during dormancy as the blooms emerge on the new growth the plant will make.
The Oakleaf Hydrangea behaves the opposite way. Cutting the oakleaf back in dormancy will compromise the next season’s bloom as the flower needs the old wood to blossom.
Finally, we wanted to mention the lilac shrub as it’s a favorite in many gardens. The lilac blooms on old wood, so if you want to do any trimming to this plant, it should be done a few weeks after it has bloomed so it has the remaining growing season to make more blossoms.
Here are examples of woody perennials:
We hope this has been an informative segment and has you thinking about the perennials in your yard. Just as the growing season has its plant care suggestions, the dormant season carries the same.
If you have additional questions, please consult a professional in your area.
“Garden as though you will live forever. ”Thomas Moore