Growing Zoysia (warm season grass) in Illinois

Whether you are thinking of starting a Zoysia lawn or just looking for some pointers on maintenance, proper cultural practices are important. This is especially true here in Illinois, towards the northern limit of Zoysia’s zone hardiness. The things you can do to properly establish and maintain your turf include:

1. Establishing Zoysia can be difficult do to because of its slow growth habit.  Most Zoysia is plugged. Zoysia establishment via seed is virtually impossible as seed only germinates about 33% of the time. It is also difficult to establish Zoysia within a lawn that already has an existing grass. It is recommended to set on bare soil to reduce competition and remember to give it time to establish. Zoysia generally spreads about 6 inches per year, so even if you are setting plugs, it may take several years to completely cover the lawn. Dave Robson, U of I PSEP Specialist, recommends an annual or perennial ryegrass in the meantime to green up the bare lawn during the establishment of Zoysia.  He also said that Zoysia established bluegrass lawn can take forever and you probably will not get a good stand.

2. Zoysia prefers a slightly acidic pH of around 6.0 to 6.5. It is a good idea to conduct periodic soil testing every 2 to 3 years for necessary lime and fertilizer application. For information on soil testing in Illinois visit: http://urbanext.illinois.edu/soiltest/

3. For minimum maintenance, it is necessary to apply at least 1 to 3 pounds of nitrogen per 1000 sq ft per year. This can be accomplished by applying a complete fertilizer three times a year in April, June, and August. It may also be beneficial to apply potassium in September to improve cold tolerance and winter survival.  Also, remember the previous fertility recommendations are only for minimum maintenance.  For dark green, high quality Zoysia, apply 3 to 4 pounds of nitrogen per 1000 sq ft per year.

4. If properly fertilized, Zoysia will require consistent mowing kept to an optimum height of about 1 inch. This is best done by mowing once a week. If needed, cut it twice over a period of 3 days and remember that if you cut a 3rd of its height or more at once, it can cause shock. It is best to use a reel mower with Zoysia that cuts with more of a scissor action. This works better for mowing dense grass at low heights. However, a standard rotary mower will do just fine if you keep the blade sharp.

5. Thatch accumulation is one of the most common problems with Zoysia, because it can harbor insects and disease causing organisms. If thatch is allowed to accumulate to greater than 3/4 inch, it can impede oxygen and water movement and raise the turf away from the soil. Remove thatch in mid to late spring every year or two depending the amount of fertilizer used.  In addition, soil should be core aerated/plugged at least once every two years to promote a healthy root system. 

One disease to watch out for with Zoysia is large patch, a close relative of and similar to brown patch of cool season grasses. Symptoms of large patch generally present themselves in spring and fall as Zoysia enters and breaks dormancy. Rapid growth during the summer months can mask the development of disease. Symptoms initially present as small patches (less than a foot) where leaf blades show a tan orange color. Areas will expand into large, (up to 20 ft) well defined patches. The pathogen will survive locally in turf debris and is favored by increased levels of thatch. More information on large patch can be found at http://www.extension.purdue.edu/extmedia/BP/BP-117-W.pdf

(Blog written by Nick Prudhomme, U of I Plant Clinic Student)