By Rashelle Matthiesen-Anderson
Plant Disease Clinic
Iowa State University
It might sound crazy, but autumn is my favorite time of year for gardening. What could be better? There are no mosquitoes, the temperature isn’t scorching and the weeds are at bay. So, preparing my flowerbed for winter can be quite enjoyable; however, it is also a necessity. There are several steps to successfully preparing your flowerbed for the winter season, therefore ensuring a healthy bed in the spring.
The removal of annual and herbaceous plant debris from the flowerbed is very important. Proper sanitation decreases the chance of disease and insect problems in the spring. Diseases and insects like to use debris as over wintering “hiding places” and they can then cause serious damage to plants in the following growing season.
Diseased debris should be discarded and not placed in a compost pile because temperatures in most compost piles do not get hot enough to kill all pathogens.
Another good idea is to remove annual flowers after a killing frost. In addition, perennials that show signs of disease should be cut back in the fall. Healthy perennials can be cut back in the fall or spring. Perennials that provide winter interest, such as ornamental grasses, should be cut back in early spring.
Cutting back in the spring has some advantages, which include providing winter protection and preventing premature plant growth. Most perennials can be cut at ground level. Cutting perennials back to ground level does not harm the plant because, in the fall, perennials transfer their nutrients to the roots.
After removing the plant debris, the soil in annual flowerbeds can be improved by applying and incorporating organic matter, such as compost or well-rotted manure. Using a rotary tiller when adding compost can improve annual flowerbed health because it reduces compaction, increases drainage and increases organic matter. Although tilling can be time consuming and strenuous work, it does provide a wonderful way of incorporating organic matter into the flowerbed.
Tilling perennial beds or a mixed annual and perennial bed is not recommended as tilling could damage perennial root systems, which could slow or prevent plant growth in the spring.
If using a rotary tiller is not feasible or the flowerbed contains perennials, applying 2-3 inches of mulch to the flowerbed also is beneficial. Newly planted perennial beds should be mulched in late fall. Pine needles and straw can be used as winter mulch for newly planted perennials to prevent damage from freezing and thawing conditions, which may heave poorly established plants out of the ground. Plants heaved out of the ground may be severely damaged or destroyed. However, most well established perennials do not require protective winter mulch. If desired, wood chips or shredded bark can be applied as permanent mulch to well-established perennial flowerbeds.
Before applying mulch, remember to remove all diseased plant debris and weeds from the flowerbed. Adding mulch to the flowerbed ensures roots systems are covered and better protected for the winter. In the spring, remove most of the mulch from annual flowerbeds and incorporate approximately 1 inch of mulch into the soil. Mulch adds organic matter to the soil, which creates a healthy environment for plants. Winter mulch should be removed from perennial flowerbeds in late March or early April.
Finally, water perennials when the weather in late summer and fall is dry. Even though the temperatures are dropping, plants are not dormant yet. In the fall, humidity usually drops and the air becomes dry. These conditions combined with a stiff wind can quickly dry out soil. So, remember to water before the ground freezes if conditions are dry.
Although fall might seem like the time to just sit back, relax, and enjoy football games or walks in the park, don’t forget that your flowerbed needs you. By taking the time now, you are ensuring the good health of your flowerbed in the spring and years to come.