Replacement of St Augustine

chap914 – posted 15 May 2007 02:01

In the community where I live, I have noticed that many areas appear to have a “worn out” appearance. To me, the cause seems to be that the turf-grass is being cut at a low height of approx 1 1/2″ in an effort by the landscape contractor to hide crab grass and other weeds (my experience is that weeds look better when cut short). The contractor claims that the turf grass is old and worn out and needs to be replaced.

This leads to my question – Is there a time period (number of years) when St Augustine needs to be replaced or can it be maintained fairly indefinitely through proper maintenance, fertilization, cutting methods, etc.?

TexanOne – posted 15 May 2007 04:07

St Augustine (or any other rhizome / stolon turfgrass) can be maintained indefinitely and does not need to be replaced. Cultural practices such as turf aeration, fertilization, irrigation, and adding organic matter to the turfgrass will maintain a healthy stand of St Augustine for a lifetime. There are many examples of St Augustine turf in my city that are at least 50+ years old and are very beautiful.

Non rhizome / stolon producing turfgrasses – such as bluegrass and fescue do have to be refurbished after several years since they tend to die out from insect and environmental problems and cannot spread into the areas of turf loss.

TexanOne – posted 15 May 2007 10:36

It is also interesting to note the landscape contractor is aggravating the weed problem with such a low cutting height. St Augustine is one the best turfgrasses for naturally suppressing weeds because of its thick growth habit – but only at the proper cutting height of 3” to 4”. St Augustine cut at 1 ½ inches will be stressed, thin, and prone to weed invasion. You also need to verify you are not dealing with a disease or fungal issue that is causing the St Augustine to be thin or worn-out looking.

If you are paying for the lawn services, I would insist the contractor raise the mowing height, and to only cut the St Augustine at 1 ½ inches in late winter / early spring to remove any winter-damaged top growth. Otherwise, the cutting height stays at 3” to 4”.

I would also recommend the St Augustine be vertical core aerified to relieve soil compaction every 2 – 3 years, and top dress the post-aerified turf with an organic mulch such as composted cow manure, or common organic compost at least 1x/year. Also continue with a regular turf maintenance program of irrigation and fertilization.

The last thing I would do is roto-till and replace the sod. In 30 years, I have never had to roto-till a turfgrass area yet. Hope this helps…

chap914 – posted 18 May 2007 03:12

Texan – when you refer to mowing heights of 3″-4″ are you refering to the height of the mower deck or the resulting length of the blade of grass after cutting? I believe I have a good deal of thatch so that the mower sinks in thereby scalping the grass. Suggestions?Thanks

TexanOne – posted 21 May 2007 01:00

When I say 3” – 4” cutting height, I am referring to the cutting blade being 3’ – 4” above the wheel height at point of contact with the turf.

If you have thatch or if the St Augustine is spongy to the extent the mower sinks in during cutting, it may be time to de-thatch. The problem with de-thatching St Augustine is that it does a lot more damage to St Augustine than other turfgrass species and it will take months to recover. However, you may not have any choice but to just do it and nurse the damaged St Augustine back to health.

Before I would consider de-thatching the SA, I would take a core sample to see exactly what was going on and why the turf is spongy. Excessive thatch buildup is an abnormal condition caused by either one or more unhealthy cultural practices. Usually, excessive nitrogen fertilizers are being used and/or inadequate microbial life in the soil to break down the dead stolons and clippings are major contributing factors.

I would recommend cutting down on the use of high nitrogen fertilizers and introducing biological controls (top dressing with organic mulch) to start. Depending on how bad the thatch layer is, I would first attempt vertical core aerification, and as a last resort – verti-cutting the entire lawn with a vertical mower. Even if you have to go with the most radical procedure and verti-cut, you should not have to re-sod. At any rate, if you do renovate the SA turf, bear in mind thatch buildup is generally preventable and with proper cultural practices, you should not have to do this messy and tedious job again.

Another idea to ponder: About ten years ago, I introduced hundreds of earthworms into my turfgrass to improve the rocky, poor soil I had. There are now thousands (or millions) of the little critters that have transformed my soil into a rich, dark brown, clay loam. I suspect they have also kept the SA thatch in check by naturally aerifying the soil. In short, you must have a good biological ecosystem going in the soil to achieve sustainable thatch control. Hope this helps…