When are we to cut back our plants? What plants are we to cut back? So often I am asked these questions when we have installed a lushes planting, teaming with perennials. I sometimes think it stems from overwhelming reasons! But from these questions I begin my discussion for the day about the importance of winter interest.
Winter interest is sometimes lost or forgotten about when designing a landscape. In our climate evergreens are mostly what is found with leaves attached during the winter season. So designing a landscape with evergreens is a must or an easy way to achieve this winter interest... BUT not all evergreens work or fit in all micro climates and settings. Some, the winter sun or wind are just too much for them. Snow can hide or damage the plant leaving it deformed for the next growing season. Others are just too darn big! So we use woody or deciduous shrubs and herbaceous plants to add this winter interest. Leaving out trees for this discussion, because of size, there are many shrubs that offer unique winter stem color or texture. Take a red twigged dogwood, Cornus alba 'Sibirica', for example. Its vibrant red stem burned by the sun in the fall and winter have clients almost waiting for the winter to come around to show it off. Or what about the Serviceberry, Amelanchier alnifolia 'Regent', with its unique gray stems and black fruits that are not only attractive to humans against the white snow but birds make the best of them. Even though deciduous shrubs often are a great part of the winter landscape there are far more herbaceous plants to select from in our pallet.
But how can herbaceous plants help with winter interest? Do we really want to install thousands of dollars of perennials and not have them add to the other 4-5 months out of the year? So the simple answer to "When to cut things back?" is early early spring, with some exceptions. Below are two links that will help one choose these exceptions. I love the look of Blazingstars, Liatris pycnostachya, in the late fall when the frost is on the ground their leaves are a burnt orange and seed heads holding fast for the long winter season. Blazingstars are only one of tons of perennials which keeps their seed heads straight and sturdy throughout the winter. Winter sun, wind or snow these plants show off a integral part of the plants cycle of life. Another common seed heads that we can all distinguish is the Black Eyed Susan, Rudbeckia, or the Conflower, Echinacea. These usually found in large groups are such sturdy crops sometime snow will be elevated on there tops like pillows of clouds. Without confusing the situation, another herbaceous plant that holds its own throughout the winter are ferns and grasses. Grasses lend us the largest in height of the seed heads dancing in the winter breeze most standing until the damp spring or the fare between ice storm. My favorite of the grasses is the North Winds Switch Grass, Panicum virgatum 'North Winds', or the Shenandoah Switch Grass, Panicum virgatum 'Shenandoah'.
Some perennials just don't seem to make it through the winter season with any kind of real winter interest. Daylilies and Hostas are two such plants that may have a straggling used flower stem whimsically standing above the snow but for the most part really do not show well in the late fall or winter. These plants are sometimes even harder to remove there expressed above ground plant stock in the spring. The leave tend to be saturated and hard to gather. Rather it is better to cut these back in the late fall when you can easily scoop, twist and cut off 95% of the used plant. If it was not cut back in the fall I would suggest raking it gently and leaving this plant material as it is often more damage then what it is worth to remove it.
Either way, fall or spring to cut your herbaceous plants back you will probably be ok and the plants will be as well. But I hope with my entry here I can simply make you look twice at a perennial seed head holding strong throughout our tough winter climate and enjoy the beauty that lies in this part of the winter interest.