August is all about the Z-Grass!

Zoysiagrass needs TLC in August

In direct contrast with cool season lawns, which shouldn’t be fertilized with high nitrogen in the sultry months of July and August, zoysiagrass, and it’s hooiser cousin, bermudagrass, LOVE nitrogen and heat! Zoysiagrass and bermudagrass are WARM season grass species. For those of you that vacation in the south, they have additional varieties like paspalum, St. Augustine and centipedegrass, all of which have broad leaf blades. The latter three species can’t handle the cold weather. Zoysiagrass is more cold tolerant than bermudagrass.

A great program for zoysiagrass in the transition zone follows:

  1. A thick and healthy zoysiagrass lawn may not even require a preemergence application for crabgrass! If you have a weaker lawn, or one you’re trying to establish, apply a crabgrass preventer in mid-April on a fertilizer with at least 18% nitrogen. Apply the crabgrass product as late as possible, when the soil temps approach 50 F. You really don’t want to put this down on dormant zoysiagrass. Our local meteorologists on Fox 2 in STL give soil temperatures in the early spring, so pay attention to their forecasts!
  2. Systemic Insect Control on a High Nitrogen fertilizer should be applied in mid-June. Zoysiagrass has more problems with billbugs than grubs, and the systemic products control both. Professional bags are 50 lbs and will treat 12,500 sq ft to 14,400 sq ft. This bag will last 2 years no problem. If you can’t find a professional supplier you can purchase a systemic insecticide at Home Depot or Valley Park Elevator. Your z-grass needs 0.75 to 1.0 lb of actual nitrogen per 1,000 sq ft. To calculate how much nitrogen is in the bag, multiple the weight of the bag times the % nitrogen (first number) in the bag. For example, a 36 lb bag of 24-8-12 has 8.6 lbs of nitrogen (36 X 0.24). Round down to either 8 or up to 9 without worry.
  3. One last shot of nitrogen between July 24 and August 15. Again, 0.75 to 1.0 lb of actual nitrogen.
  4. NO MORE NITROGEN THE REST OF THE FALL!

MOWING RECOMMENDATION:  Zoysia does better when it’s mowed low. As low as freakin’ possible! If you mow it high, it won’t spread very aggressively. When you mow it low, it’ll spread very nicely for you. Z-grass has a tough leaf blade so keep the blade razor sharp. Don’t mow more than 8 times without sharpening or changing your blade for best results. A lawn mower engine won’t last as long mowing Z-grass as it does a cool season species. If you’ve got a small lot in the city, get one of those new, lightweight “reel-type” mowers. Those are kick-ass for zoysia because the cutting action is “scissors-like”.

WATERING RECOMMENDATION:  Z-grass really only needs an inch a week to grow well, because it is adapted to hot weather. We have to water the crap out of our bluegrass and fescue lawns to keep them from going dormant! Stop watering zoysiagrass after September! Let it start to go dormant in October.

AERATION AND DETHATCHING:  You should NOT aerate or dethatch zoysiagrass unless it’s 100% green and growing. Do this in early June when the temps are tolerable for you to clean up the mess. Water and fertilize when you’re done. Mow low and watch that sward develop!

Many of the lawns in St. Louis are blends of both cool season lawns and zoysiagrass lawns. Bermudagrass is a weedy invader via bird poop, but zoysiagrass doesn’t become established the same way. If you don’t want the warm season grass to expand, then be sure to AVOID passing through these areas when you aerate, because you’ll “spread the sprigs” in the cores! If you desire more zoysiagrass in your cool season sward, then aerate around mid-August. Be sure to water to allow the small pieces of stolons and rhizomes to become established.

FUNGICIDE IS OCCASIONALLY BENEFICIAL:  Zoysiagrass in St. Louis was plagued with a disease called zoysia patch during the summers of 2013 to 2016. It was devastating to many lawns, especially for those of you that followed the cultural recommendations for cool season lawns. Factors that exacerbate zoysia patch are aerating/dethatching before June or after September, watering all fall and fertilizing after September.

The pathogen that causes zoysia patch is Rhizoctonia solani, but a slightly different sub-species than the one that causes brown patch in cool season turf! Fungicide applications are really only useful when daytime temps are near 70 F. Apply Headway G fungicide in the fall and again in the spring. If you can’t find Headway G combine the two products you can buy at Home Depot–azoxystrobin and propiconazole. It is very important to time the application to 70 degrees! This is because of the infection cycle for the pathogen.

Here are a few shots of zoysiagrass, mowed at three inches, which is very common in St. Louis. The photo on the left is all zoysiagrass, while the photo on the right is the interface between zoysiagrass and the cool season species.

A new variety of zoysiagrass has a slightly darker green color than ‘Meyer’, the long-dominant variety in our area–called ‘Zenith’.  Emerald View Sod Farms in Columbia IL and O’Fallon MO carry this variety. Call them and ask if you can get it here in town. Or, just go there.