What a difference a year makes, or even a month! After dealing with wildfires and burn bans all winter, now we are coming off the wettest month ever for rainfall in Oklahoma, and so far the month of May is putting up some pretty impressive rainfall totals too. So, while it’s good that the subsoil now has moisture, the ponds and lakes are full, and we can save money on our water bills, there are also negative effects of excessive rainfall on plants and turf in the landscape. As with most things, too much of something good can often be just as bad as not enough.
Remember learning about photosynthesis and respiration in science class way back when? I’m a science teacher by trade, as I was a teacher for 8 years before becoming a lawn care operator. So allow me to pull out my old overhead projector and give a brief lesson on how this excessive rainfall can affect your lawns and landscapes.
Plants need oxygen to live, since it is a component of the respiration process in combining with sugars (produced from photosynthesis) to produce water and energy the plant needs for growth. The root system of plants absorbs that oxygen from tiny pore spaces found in the soil. However, when the soil is constantly saturated with water from rainfall, or excessive irrigation, these pores are filled with water and not oxygen. Therefore, this lack of oxygen uptake from the roots can result in death of some of the root system, leading to dis-coloration of foliage, wilting, and sometimes even death of the plant. Certain plants, and plants planted in poorly-drained soil are more susceptible to damage. If you lose plants during this rainy time, you may consider improving the drainage, or changing to a hardier plant. Certain trees can show a color change in leaves, and/or have leaves drop. It’s no cause for concern usually, and with drier weather will go away.
With our unique 70% slow-release nitrogen fertilizer applied back before all this rain hit, our customer’s turf really should be fine, since most of the nitrogen is water-insoluble and not as prone to leaching or washing away as water-soluble quick-release N sources. When the soil stays completely saturated for weeks on end, the turf roots will be damaged, so we’ll need some drier and warmer weather to help the roots recover. Until that happens, most turf will just not look as good as it normally would at this time of the season. However, when the soil stays saturated, the pre-emergent in the soil will break down sooner, so we do expect to be dealing with more weed issues this summer.