Answer: Weed control in zoysiagrass occurs in two ways: by preventing the weed seed from germinating each year and by killing weeds that already exist.
Products known as pre-emergent weed killers are used to prevent weed seed from germinating. There are several different chemicals and products available. They differ in the kinds of weed seed they control and the length of time the product remains active.
Pre-emergents should be applied before the weed seed germinate. For summer weeds, Like crabgrass, apply the chemical in spring after night temperatures have been in the 60's for four days around the time forsythias bloom. For winter weeds, like annual bluegrass, apply the preemergent in early October. Most products need to be watered into the soil after application.
Other weed killers are used after the weeds have emerged. There are different products for grassy weeds, like goose grass and broad leafed weeds, like dandelions. Onions are considered a broad leafed weed. These post emergent chemicals are used when the weeds are actively growing, early in the summer.
It is important to know the name of the weed you are trying to control before using any weed control chemical. Once you know the weed, it is simple to read the label of a weed control product to see if it works on your weed. Also be sure to check and see if the chemical can be applied to your lawn grass without harming it. Never apply more of the chemical than the label recommends. Double doses of herbicide can kill your entire lawn before you know it.
Established zoysiagrass requires less fertilizer than many other species for healthy, attractive turf. A seasonal total of 2 pounds of nitrogen per 1,000 square feet is ample. Excessive or untimely fertilizer applications can lead to problems such as fewer roots, more thatch, diseases, and more topgrowth that requires increased mowing.
For best results, soil testing is recommended before fertilizing. A soil test will indicate major nutrient deficiencies and the acidity or alkalinity (pH) of the soil. Slightly acidic soil pH (6.0-6.5) is best. Lime should be applied only if the pH is less than 6.0.
Established zoysiagrass should be fertilized from May through August. Early spring (March/April) fertilization benefits weeds and promotes premature topgrowth before roots begin to grow. Late fertilization (September) may interfere with the natural hardening process before winter.
For routine maintenance where soil tests indicate no major deficiencies, use a lawn fertilizer with approximate nitrogen (N):phosphorus (P):potassium (K) ratio of 3:1:1 or 4:1:1 or 4:1:2. A 16-4-8 fertilizer has a 4:1:2 N:P:K ratio.
Where soil test indicates low phosphorus or potassium levels or where basic fertility levels are not known, use a fertilizer with a ratio that more closely approximates 1:1:1 or 2:1:1.
Zoysiagrass is mowed at a shorter cutting height (1-2 inches) than Kentucky bluegrass or fescue. In the spring of the year, zoysiagrass lawns may be mowed at the lowest setting on your mower to remove dead leaf tissue. This increases the greenup rate and allows easier and more uniform mowing during the growing season. The mowing height should be raised in September by 1/2 to 1 inch in preparation for fall.
When mowing, never remove more than one-third of the leaf blade at any one time. Clippings need not be collected if they do not remain as clumps on the lawn surface.
Zoysiagrass is a drought-tolerant lawn grass that requires less water than Kentucky bluegrass to remain green and actively growing during the summer months. Watering usually is not necessary except during prolonged dry periods.
A properly managed zoysiagrass lawn is very competitive with weeds. However, winter annuals, such as chickweed and henbit, can be a problem when the grass is dormant. Weeds will also invade turf after it has been damaged or weakened by insects, disease or intense dethatching.
Winter annual weeds are best controlled in the fall rather than the spring, when they bloom and set seed.
Grassy weeds, such as crabgrass, generally are not a problem in established zoysiagrass lawns. An early spring application of a crabgrass preventer may be desired while new lawns are being established or on close-mowed or regularly irrigated turf.
Hope this information helps.
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