With all of the rain we have received over the last couple of weeks and the high humidity, I have begun to notice a few issues with some of my plants and garden beds. Excessive moisture can wreak havoc on plants that are grown in containers or even in the ground. It is also a breeding ground for insects, molds, and other stressors that can affect our plants’ health. So, what should we be on the lookout for?
First of all, use caution when working around your plants after heavy rains. Try to avoid walking on or near the root systems of plants while the soil is still soggy and wet. When the soil is wet it can compress around the plant’s roots and add stress to the roots and even diminish the air pockets that supplies oxygen to your plant, thus suffocating your plant.
While inspecting your plants (at a safe distance), be sure to check the soil levels around the plants’ base to make sure there is no erosion. If you spot any exposed roots or sinkholes, gently replace the soil, or add additional soil to thoroughly cover the exposed roots.
Some plants, such as lavender, artemisia, lamb’s ears, and dianthus have little tolerance for wet soil and can die after just a day or two of excessive rainfall. Daylilies, iris, lilyturf (liriope/monkey grass), and mondo grass may not die, but some of the roots may rot, putting the plant at risk during intense heat or cold. Most needled evergreens are especially vulnerable but they do not turn brown and drop needles for weeks or even months after heavy rains or overwatering. Damage and/ or decay may not show up until months later. The end result depends on the plant species, how long it was sitting in soggy soil, and whether the plant has ideal conditions while roots regrow. If you grow these varieties of plants and your soil remains waterlogged, it may be best to dig them up and move them or temporarily grow them in a container until our weather patterns seem back to normal.
Since nature is the culprit for the excessive amount of rainfall, there is not much we can do to prevent it but we can do our best to assist in recovery. When you have found signs of root rot or a delicate plant is struggling to re-coop, if possible, move the plant to a shady location until it has fully recovered. Begin watering only when the surface of the soil is dry to the touch. Do not allow the plant to get extremely dry as this additional shock could be enough to kill it. If the plant is wilting badly, you can mist the plant’s foliage with water to help prevent leaf scorch but refrain from watering the soil before it has dried out. Do not fertilize your plants while they are recovering. With the roots in such a delicate state, fertilizing could burn the roots and kill your plant.
Inspect your plants for spots or other discoloration on foliage, as well as rotting or wilting of stems, fruit, or even the whole plant. An overabundance of moisture leads to widespread spotting, streaking, and disease-related browning of leaves, mostly caused by fungal diseases that thrive in warm, humid, and wet conditions. Blackspot and powdery mildew are examples of fungus related issues that can develop with excessive moisture that I would treat immediately with a fungicide and removal of the infected leaves. Plants usually outgrow most leaf diseases, although they may look bad and drop leaves prematurely. It can take weeks for new leaves to begin growing, so don’t give up on your plants immediately. Be vigilant to remove any infected or decaying leaves and throw them directly in the trash, not the compost pile. We want to remove all unseen spores away from our plants as soon as possible to keep the infection at bay.
You may also notice excessive amounts of mushrooms or mold around your plants on top of the soil. Mushrooms are actually a positive sign that you have healthy soil. Underground, below the mushrooms, are threadlike networks called hyphae. Some attach to plant roots, creating filaments that reach far into the soil, increasing the surface area of plant roots up to a thousand times. Fungal hyphae and plant roots working together are called mycorrhizae. A thimbleful of soil can contain miles of mycorrhizal filaments. The mycorrhizal filaments of fungi also produce organic compounds that glue soils together and improve their structure and porosity to enhance root growth. In addition, mycorrhizae in the soil have been found to suppress soil-borne pathogens and protect plants from root diseases. Mycorrhizal fungi are not fertilizers, although a fungal inoculation of roots can improve a plant’s growth rate and tolerance to drought and disease. Despite their benefits to soil, you might want to remove mushrooms from your yard if you are worried that they could be poisonous and harmful to children or pets. Simply rake them and bury them in the compost pile.
Most molds that will show up on top of your soil from excessive moisture are harmless to your plants. I generally will just remove about 2” of the soil that has mold spores growing and discard and replace with sterile soil. You can also use a fungicide or ground cinnamon to help eradicate the spores. If possible, set the plants in direct sunlight for a day or two, as UV Rays will also destroy the spores. Generally, after the rains have passed and the plant dries out, the mold spores will become inactive. If you feel the need, simply replant in fresh sterile soil. When in doubt, I always repot. TIP: Did you know that you can sterilize soil in the microwave? Place 1 qt of slightly moist soil in microwave safe container and cook on high for 2 minutes and then at short intervals to reach 200 degrees (F).
Charla Ingram is a plant, nature, and golfing enthusiast who, along with her husband Chris, owns and operates C&C Gardens in the small town of Bessie, Oklahoma.