Question
Hi, I have a question regarding floratam ST. Augustine. I currently have Raleigh ST. Augustine here in the Rio Grande valley. I don抰 know if it抯 because of the very hot weather or that we have heavy clay dirt.  After seeing my lawn yellow and the grass not thriving,   I was told to buy floratam.  When our house was built the contractor added fill dirt and it ended up being very heavy black clay. Will floratam grown  on  heavy clay soils?  I plan to do  3 foot rows of floratam and hopfully it will take over the Raleigh.  



-Roger


Answer
I assume you are trying to cultivate a nice Lawn in one of the four 'Rio Grande Valley' Counties:  Starr, Hidalgo, Willacy and Cameron.  Designated 'South District 12' for Texas A&M purposes.  Please correct me if I'm wrong.  Otherwise, all systems are go here.  Let us proceed:

Your high/low temperatures puts you in USDA Zone 9, but that doesn't begin to describe the climate extremes of this region.  In the coldest month, January, the thermometer plunges to a balmy 50 degrees or warmer on a cool day; highs are typically furnace-range between March (78 degrees average, record high of 106 degrees F) to 84 degrees in October.

Statewide stats show that most Texas Lawns are built of St Augustine, Bermuda, Buffalo, Centipede, Tall Fescue or Zoysia (either Z matrella, the original Zoysia from 1911, aka 'Manila Grass'; or Z tenuifolia, aka 'Korean Velvetgrass' or 'Mascarenegrass').  But there are a lot of climates, because Texas is a big state with a lot of weather.  In your case, although you've had a dry spell, you are about to get a TON of rain, according to the weather bureau.  So keep that in mind when you look at your Yellow Grass.

The most heat tolerant Grasses in your region are Bahiagrass, Bermudagrass, Centipedegrass (but only on Sandy Soils with EXCELLENT drainage), St Augustine, Zoysia and Buffalo Grass (preferred in the dryest areas that get less than 20 in of precipitation annually).

I often consult the National Turfgrass Evalution Program results for guidance in these matters -- regional centers grow a bunch of grass varieties, record the results and put them all together.

Trouble is, when they did the latest NTEP work on St Augustine Grass, the Texas location they chose was a plot of light, Sandy Soil with a pH of 7.6 to 8.5.  Very different from your heavy Clay description.  So we can't trust the NTEP records.

I should tell you that St Augustine can be something of a disease magnet when it comes to growing a Warm Season Lawn under traditional turfgrass management methods.

But the 'Up' side of St Augustine keeps it very popular on the short list of Warm Season Grass options.

So the research continues.  And one result of that result is a variety of something you could not consider growing in South Texas, a hybrid called 'Reveille', studied as Brand TXKY-16-1 by the Texas A&M researchers.  Key market for Reveille is a little North of your location, in Central Texas as well as South Oklahoma.  Reveille was bred for mega-drought tolerance.  It also boasts an ability to take an ununusal dose of high heat (a trait no one has been able to pull off in a Bluegrass before Gardner Turfgrass unrolled its Reveille).  It is exceptonally heat tolerant, and less susceptible to the common ailments like Fall Armyworm and Rust.  You can read more about it at the website its developers set up to promote it:  reveilleturf.com

More than the variety of Grass you choose, however, is the symptoms you have described.  Your Lawn turned Yellow -- Chlorotic.  The quick fix most people come up with for Chlorosis is a treatment of Iron.  But most Soil -- especially Clay Soil -- has PLENTY of Iron in it.   Much of Texas in fact has Soil packed with Clay as its main ingredient.  In heavy rain conditions, this can be a burden on any root system.   Because plants ONLY make Chlorophyll while they're breathing.  And they can't do that when their leaves are under water.

So now we get back to the subject of Chlorosis.  Symptoms appear after a period of cool, wet weather, and even more often when the Soil is somewhat compacted, testing very high or very low pH levels or way too much Phosphorus as a result of years of build-up of all purposes chemical fertilizers...  When all they have to do is adjust their Soil.

Because more than the variety of Grass you select, the beautiful American Lawn has EVERYTHING to do with your Soil -- what's there, what's not there, and what you can do about it.

So: PLEASE get your Soil tested.

You can have that done, for a modest fee, same price as a couple of gallons of Texas Tea, either at the Texas A&M lab:

soiltesting.tamu.edu

or at one of the Cooperative Extension offices near you:

Starr County - starr-tx.tamu.edu
Hidalgo County - hidalgo-tx.tamu.edu
Willacy County - willacy-tx.tamu.edu
Cameron County - cameron-tx.tamu.edu

Now, just to backtrack for a moment, parts of Texas experienced a veritable deluge of rain last Summer.  The flooding was cited as the main reason for Chlorosis on Lawns.  Aerating those Lawns was the most effective treatment; opening up the roots to Oxygen helped heal the roots, took control of the anaerobic bacteria that were attacking them, and supported overall turfgrass health.  And the ending was a happy one.

But this is a new season with new problems.

Your 'Raleigh' selection was based on a cultivar introduced in North Carolina back in 1980.  Because of its cold tolerance, it has been most successfully in parts of Northern Florida, and is in particular known for growing well in HEAVY SOIL with a HIGH CLAY CONTENT.  It is also know for HATING the HEAT of Summer.

'Floratam' is an even older variety.  It came to market in 1972 as a SHADE and DROUGHT tolerant selection, equalling 'Floralawn' in that category.  But it can't take a chill (not a problem where you live).

Just for the record, Zoysia absolutely has no tolerance for bad drainage.  Your Clay Soil takes out of contention both Zoysias mentioned above.

A little research into my notes on your local country clubs tells us that the most favored Grass for tee'ing off on the Greens and Fairways of South Texas is NOT St Augustine, NOT Zoysia, NOT Bluegrass... it's

BERMUDAGRASS!

Yes, the Valley International Country Club, the Brownsville Golf Center, River Bend in Brownsville, the Ft Brown Municipal Golf Course, Harlingen's Treasure Hills Club, Tony Butler Golf Courses (2) -- these all voted for Bermudagrass.

Just what switching to Floratam is supposed to do for your situation, my friend, well, I don't know what to say.  Educate me please if you have any information.  There's always something new to learn in this business.

That said, I can't see any reason you would not pick Bermudagrass, a species that loves a good, hot day with lots of Sunshine.  It will however need a serious, effective correction of your Soil to work.  Before you pull out the Kleenex, let me point out, without going on too much longer on this as I don't want the website to crash with my ongoing long long answer, let me just point out that Clay is the perfect place to start a Gold Standard Lawn.  It has all the vitamins and minerals a healthy blade of Grass needs to grow not just big and strong, but bold and beautiful.

And on that note I wish you a lovely day.  Your followup welcome but it would be better posted on a separate question -- and I would very much appreciate a nomination to the AllExperts hall of fame because I do like to get on that 'Top 100' list.  I apologize for taking so long to put this all together. My typing is a bit slow.

Thanks for writing.  Remember, get your Soil tested.  All the best,

L.I.G.