Waterlogging Influence on Turfgrasses
A number of homeowners have noticed their tall fescue seeding from fall 2020 is not looking so good. Our numerous rainfall events the last few months has put us well above average in rainfall amount through February and kept our heavier soils saturated. Some have wondered if this has “drown” their young seedings.
Before we get to the seedling stage, it is important to know that tall fescue will not germinate under an anoxic environment. Which is another way of saying, seeds need oxygen during germination. So if tall fescue was planted in super-saturated soils in the fall they would have no chance to germinate until the water receded. The good news is that most seeds can exist in waterlogged soils for several weeks without permanent damage. Continued low soil oxygen levels from saturated soils can reduce total germination. So, your fall seeding may not have provided as dense a turf if your site had a lot of rainfall and poor drainage.
Once the seeds have germinated, tall fescue and bluegrasses grow well in wet soil conditions. But extended flooded conditions can result in further turfgrass losses. Research found that early established seedlings subjected to waterlogged soils for 28 consecutive days may be reduced by 46%. Also this condition can favor annual bluegrass (a prominent weed) growth over tall fescue since bluegrasses have been found to be more tolerant of saturated soils than tall fescue.
So if all that standing water thinned your tall fescue, what are your options? In the short term, you could add more seed this spring (if no preemergence herbicides were applied). This is really just a temporary solution since spring-seeded tall fescue rarely lives through the summer heat. But if you want to strengthen your existing stand, that is your best option. A more aggressive spring fertilizer program to promote more tillering of existing tall fescue plants can also be beneficial.
Also it should be mentioned that extended saturated soils are well known to cause problems with zoysiagrass green-up in the spring. It is too early to know the full impact on zoysiagrass, but I anticipate the excess soil water will cause problems.