Long before gardeners were running around with pruning tools, Mother Nature was tending to her plants with her own form of pruning. In nature, pruning is done on a much grander scale with tools such as wind, ice, fire, disease and snow, just to mention a few. There is even research to suggest plants do their own self pruning by a process called programmed senescence.
Senescence is thought to be controlled by hormone triggers causing mature leaves and roots to be pruned (die off). The reasons plants prune themselves usually result from lack of efficiency in production of nutrition or energy is needed elsewhere in the plant serving a greater good for the overall growth.
So why did man start to interfere if nature had it under control? The art of pruning has been around for a long, long time. There are many mentions of it in the Bible and even in ancient text dating back to 1500 B.C.
Man realized that pruning could increase the bounty of food, such as grapes for wine. As we have evolved, the need for pruning has too; we still prune to increase fruit and flower production, but also for aesthetics, protection of our homes and promoting health of the plant.
As the growing season for most things comes to a close, many folks like to prune, trim and cut to make everything neat and orderly for the winter. This is not typically what nature does. For many plants, this could be decreasing growth rates and/or even killing them. There are many reasons that some plants should not be pruned in the early fall and are better left looking a little unkempt. One reason is that they add interest to the winter garden.
An example of this would be the ornamental grasses waving in the breezes or layered with the occasional snow or ice. These grasses may also be shelter for wild life or beneficial insects during the cold winter months. Some plants may even stay green if the winter is milder than usual like foam flower.
Other plants, such as coneflowers, have seeds supporting the birds with much needed food for the winter. These seeds could also be necessary for self-seeding, as in the liatris family. Sometimes the dead leaves act to protect the new growth from early frosts, such as hostas. With butterfly weed, the fallen foliage protects the crown from the harsh winter winds and cold.
Yet there are other plants, such as plumbago, that do not emerge until very late in the season, and its dead stalk may act as a marker to let you know where it is sleeping. This does not mean pruning shouldn’t take place in the fall. There are some plants that do better with a trim.
Certainly any plant with disease, pests or damage should be pruned, as should any plant causing potential damage to a home or property. There are plants, such as blackberry lily, where the fallen leaves may cause the crown to rot or create problem sites with insects, such as borers in bearded iris or leaf miners in columbine.
Daylilies, catnip, blanket flower and crocosmia all perform better if trimmed in the fall. Therefore, everything should not be ignored until spring. A good resource on pruning is “Care of Ornamental Plants in Landscape” by Gary L. Wade and Beverly Sparks for your general information on when to prune some of the different plants found in our area.