(News article for May 27, 2023; edited)
Of the six springs I’ve been working in Extension in Louisiana, I’ve received more questions about lawn problems this year than any other.
I think that one of the major contributing factors to the problems we’re seeing is the cold weather we had in March. After lawns had begun actively growing, they were hit with temperatures of approximately 26 to 28 degrees Fahrenheit. Plants, including turfgrasses, are more cold tolerant when they’re dormant and less so when they’re actively growing.
Some lawns may have also sustained damage in the fall, when many of us experienced our first freeze unusually early, in mid-October. Lawns that were not fully dormant by the time we had temperatures in the low 20s in December likely suffered from that, as well.
As you might remember from taking tests in school, sometimes the answer isn’t just A, B, or C, but “all of the above.” Besides the cold temperatures, other factors could have played a part in the damage we’re seeing.
If fertilizer or a weed-and-feed product containing nitrogen was used after August or prior to the March freeze, the grass may have been more cold sensitive than it otherwise would have been. Also, lawns with thatch tend to have roots growing in the organic matter layer, where they’re more sensitive to cold.
The dry period last September and October likely stressed many unirrigated lawns. Some yards have areas with compacted soil. Some grass has likely been injured by herbicide applications at higher-than-labeled rates.
Where soil pH is too low or high for the respective turfgrass, or where certain nutrient levels are too low or high, grass is not as healthy as it could be.
A couple of diseases – large patch and take-all root rot – can cause symptoms similar to what we've seen this year, but from what I’ve observed, I don’t think these are playing a major role in most lawn issues right now. Likewise, several insect pests are commonly found in lawns, but I haven’t yet identified a current infestation of one of these as the culprit this year.
If large areas are dead, you may need to consider reestablishing grass, but where small areas are dead, grass from surrounding areas will likely fill in over the growing season if it’s healthy.
If you haven’t taken a soil test in several years, I would suggest doing this to make sure that soil pH is appropriate for the type of turfgrass you have and to see if levels of nutrients such as phosphorus and potassium need to be adjusted. Nitrogen applications can be made on a default basis according to the type of turfgrass, as addressed in a recent article.
Check for soil compaction. If you try to stick a knife into the soil when it’s neither very wet nor very dry and the blade doesn’t go into the ground easily, the soil may need to be aerated. If you walk across the lawn and it feels very spongy (and not because the soil is wet), dethatching may be needed. Late spring and early summer are generally good times to aerate or dethatch. A core aerator with hollow tines can accomplish both jobs. If you only need to dethatch, a vertical mower works well for this purpose.
During long periods with no rainfall, you can provide the equivalent of one to two inches of water per week to keep grass growing. If you irrigate, do so in the early morning rather than late afternoon or evening. Watering late in the day increases the chance of disease problems since grass stays wet for a longer period.
Let me know if you have questions.
The turfgrass section of the LSU AgCenter website also provides an abundance of information.
Contact Mary Helen Ferguson.