Why Cutoff Perennials?
Along with cooling Minnesota temperatures and fading sunlight, fall brings special maintenance tasks for perennials. One of these tasks is the removal of foliage by cutting off the plant at ground level. This is recommended for aesthetic purposes as well as for the health and longevity of the plant.
As fall nears the lovely aesthetic of perennials in the garden begins to fade, warranting removal of parts of the plants. Foliage, once lush, becomes dull and spotted. Flowers shrivel and fall; new growth ceases to be produced. Nutrients exit the foliage to be stored in the roots, leaving the greenery to wilt above ground, and rotting foliage becomes unsightly and even can begin to smell. For these reasons, foliage is removed from many, common perennials to prepare the garden for a new kind of beauty in the winter.
Removal of foliage is also recommended for the health and longevity of many perennials. It is common for fungal pathogens to infect foliage towards the end of the summer; if this infected leaf material is not removed it will predispose the plant to repeat infection the following year. While these pathogens are not immediately detrimental, recurring instances can weaken the plant reducing its life.
Many common perennials found in the landscape benefit from this foliage removal. These include: Hosta, Daylily, Catmint, Coneflower, and many others. There are some tender perennials however which should not be cut off in the fall. These species require foliage to remain on throughout the winter to survive and include Coral Bells, Gaillardia, Astilbe, and others. Plants that provide winter interest are also not cut off in the fall, fortunately these plants are less prone to harboring fungal pathogens. These include: Hydrangea arborescens (Annabelle-type, not a true perennial but often treated as such), ornamental grasses, and Sedum. Foliage of perennials that has been left on over the winter is generally removed in the spring. The exceptions to this are the semi-evergreen perennials which do not need to be removed in the fall or spring unless portions of the plant have died. These include Bergenia and Creeping Phlox.
Creeping phlox Remains
Coral Bells remain to overwinter
Sedum Remains for winter interest
The unique Minnesota climate conditions this fall of 2017 have caused certain perennials to continue blooming, and, in some cases, producing new growth longer than normal. Routine maintenance schedules result in the removal of these flowers and new growth. While it is unfortunate to cut off a plant that is yet attractive, it is in no way detrimental to the health of the perennial. In spite of this late blooming, the plants have already translocated the necessary nutrients to the roots for winter storage, readying the plant for growth next year.
Perennial cut off is an important fall (and spring) garden practice to maintain a beautiful landscape and encourage a healthy, long-lasting landscape.
Hostas with top foliage properly removed
Irises awaiting removal of top foliage
By: Cathy Nickelson, B.S. Horticulture, University of Minnesota, ISA Certified Arborist