Too much rain causes complications in gardens and landscapes

Over the last month, we’ve had quite a shift in our weather, from extremely dry throughout all of June to quite wet in July, with more rain from Tropical Storm Debby. Plants need water, of course, and since this wet period followed a month of dry weather, initially this moisture was quite welcome. However, too much rain all at once can cause some complications in gardens and landscapes.  Let’s talk about a few of these complications.
 
One of the things you commonly see in gardens following a period of wet weather is an outbreak of fungal diseases such as leaf spots and root rots. Leaf spots generally develop when the leaves remain wet for a longer than usual period of time. Root rots can be a problem for a wide variety of plants in poorly drained areas, such as heavy clay soils, or in low spots in the landscape where water pools.

Another thing you’ll often see is a surge in mushroom growth.  Mushrooms arise in the lawn or garden when there is a type of fungus present in the soil and moisture conditions are high.  Many mushrooms are nothing more than a nuisance in the lawn and garden.  They can be mowed, picked, or dug out, but will often return if the conditions stay wet.  You may notice them in low lying areas or other poorly drained spots where extra water seems to collect.  Improving the drainage or diverting water away from these locations might help with long-term mushroom control.  

Above left: Leaf spots on Black-Eyed Susans. Above right: Mushrooms popping up in lawns following heavy rainfall. All photos in this blog: Susann C., Extension Master Gardener Volunteer, Pitt County Arboretum.

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I also expect that we’ll see an increase in fire ant mounds over the next several months.  This often happens following heavy rains in late summer or fall.  Fire ants are present year-round, though the height of their mounds is dictated to some degree by temperature and soil moisture level.  When the soil is dry, fire ants typically form subterranean nests but will build higher mounds following heavy rains.  This is good in some ways, as it makes individual mounds easier to see and therefore easier to treat. 

Treatment of fire ants can consist either of a bait or drench or combination of the two methods. Bait products consist of a pesticide mixed with a food product that individual ants will carry back to the nest, killing large amounts of ants within the nest, whereas drench pesticides target the ants more directly.  At this time of the year, drench products will work faster to kill ants and break down the mound.

A somewhat pleasant result of heavy rain is that it is much easier to deal with weeds when the soil is moist. 

Top: Fire ant mounds increase following heavy rain. Middle: Crab grass is easier to pull out from moist soil. Lower: Like many weeds, spurge becomes more abundant following prolonged wet weather.

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Many weeds can grow in more adverse conditions than desirable plants, so while your trees, shrubs, and lawn struggled during the dry period in June, many weeds quickly filled in the gaps and then took over once the big July rains came.  When the weather is hot, it can be pretty tough to get motivated to pull weeds out of the dry, hard ground.

Now that the ground is soft, however, it’s a perfect opportunity to reclaim some of those out-of-control spots by pulling weeds.  It’ll still be a little bit of hard work, but even the deepest-rooted weeds can be pulled out relatively easily after this much rain.  

Matthew Stevens is the County Extension Director and Horticulture Agent for North Carolina Cooperative Extension’s Pitt County Center.  If you have questions about this article or gardening in general, please contact the Pitt County Extension Master Gardeners at [email protected] or 252-902-1705.