Q. Should I allow my lawn to go brown if rainfall is short?

A. The answer depends upon the type of grass present and how it was managed prior to the drought. In Oklahoma, tall fescue, Kentucky bluegrass and perennial ryegrass have poor drought tolerance. If these grasses go completely tan (called “leaf firing”) due to summer drought, they will be severely damaged and provide poor to moderate recovery once water is again present. The very fine textured hybrid bermudagrasses mowed at 1.25 inches or shorter, as well as Centipedegrass, St. Augustinegrass and Zoysiagrass are usually moderately thinned and damaged if they are allowed to go completely tan during a severe summer drought. For buffalograss as well as the common bermudagrasses such as U-3 and many of the seeded bermudagrass, if they were mowed at 2 inches or above prior to the drought, they can often survive several weeks while being tan with only minimal to moderate thinning/injury. There is no doubt that nearly all turfgrass stands are damaged if allowed to go tan during a drought. This means that once moisture becomes available the number of living shoots following the drought will not at first be as high as the number present prior to the drought. Properly managed lawns will tolerate an extended drought better than either under or over managed lawns. Generally, the warm-season turfgrasses will resume growth when moisture is available again and they will gradually completely cover the lawn area.

 

Q. How high should I cut my lawn this fall?

A. When too much foliage is removed, roots fail to grow deep into the soil. All turfgrasses need regular clipping above an inch in height, except for bentgrasses, which require a shorter clipping height (1/8 to 1/4 inch on putting greens). Turf type tall fescues, perennial ryegrasses and Kentucky bluegrass should be cut at 2 to 4 inches.  Bermudagrass, buffalograss, centipedegrass, St. Augustinegrass and zoysiagrass should be allowed to grow to 1/2 inch taller than the summer height to help them better insulate the soil for increased winter tolerance.

 

Q. Should I bag my clippings or leave them on the lawn?

A. A good rule for mowing home lawns is not to remove any more than 1/3 of the leaf surface area at any one time. If this is followed, in most cases it is not necessary to bag your grass clippings. Grass clippings do not contribute substantially to the formation of thatch. Clippings return valuable nutrients to the soil through rapid decomposition processes. They usually contain some nitrogen, phosphorus, and potassium as well as minor elements plants need. Some grass varieties are prone to thatching regardless of whether clippings are bagged or not.

 

Q. Should I seed my cool-season lawn this fall or wait until spring?

A. Four to six weeks before the first autumn frost is the ideal time to plant a new cool-season lawn or overseed one that has suffered through an unfavorable summer. Spring is a distant second choice for seeding cool-season grasses. Spring seeded cool-season lawns sometimes have poor summer survival as the grass is not mature going into the summer.

 

Q. Can lawn clippings treated with herbicide be used in the vegetable garden?

A. First refer to the herbicide product label since it is the law in this matter. Both post-emergent and pre-emergent herbicides used for weed control can leave residues on the grass leaves. Provided that the herbicide label does not forbid the use of grass clippings as a mulch on specific sites, at least four irrigations of one-half inch of water (or rainfall equivalent) and four mowings should have occurred before considering bagging clippings for use in the vegetable garden.

 

Q. Where can I find out when and where the next Oklahoma Pesticide Applicator Testing Sessions will be held?

A. The Oklahoma Department of Agriculture, Food & Forestry is the state agency responsible for pesticide applicator testing, certification and licensing in Oklahoma. The locations and dates of upcoming applicator testing are posted at the Pesticide Safety Education website.

 

Q. What does pre-emergence herbicide and post-emergence herbicide mean?

A. A pre-emergence herbicide is a product that is applied to a turfgrass area with intent of being put in place before the germination of a certain target weed or weeds such that the product kills those specific targets at the time when their seed germinates and attempts to put out a small root or shoot. A post-emergent herbicide is put out after the target weed or weeds are already visible to the applicator and the intent is that the herbicide kills an already germinated or emerged weed.

 

Q. Is it too late to apply a pre-emergent herbicide for crabgrass in April?

A. If you intend to control crabgrass in a turfgrass area then it is not too late. Even if crabgrass has already started germinating in your area, by applying a pre-emergent herbicide early in the month as per label directions and activating the product by watering it in with two split applications of ¼ inch of water; you will still get the benefit of some pre-emergence crabgrass control. If crabgrass has already started to germinate, you will probably need to apply a post-emergent product to kill the crabgrass seedlings once you can see the plants and before they produce more than 4 tillers. Not all crabgrass seed on a site germinates on the same day or even the same week. Use of a pre-emergent on a site where some germination has already started will still help reduce the severity of the infestation. Also, once you apply a post-emergent herbicide for killing existing crabgrass, a small opening in the turf stand occurs and you need a pre-emergent in place to suppress more germination in the opening. Due to dry conditions over most of the state, even though soil surfaces are warm and conducive to germination, the dry surface has largely suppressed germination over much of the state. Note – if you have been irrigating then you have eliminated dry surface as a restriction on germination and you may have some seedlings present.

 

Q. I had crabgrass in my lawn last year, how do I know if crabgrass has already started to germinate in my lawn?

A. If you know that you had crabgrass last year, go to the spots where it was located. Although killed by freezes you can probably see how even dead crabgrass leaves and stems look different than those of bermudagrass and obviously different than those of tall fescue. In the case of a bermudagrass lawn, the dead crabgrass plants usually have a wider leaf width, a different foliage color and plant growth habit even looks different than bermudagrass shoots killed by freezes. Part the dead or live canopy of the turf near the outskirts of the “crabgrass skeletons” from last year and see if you see rather broad bladed grass seedlings emerging from the soil. Each crabgrass plant usually sets hundreds of seed so you will most assuredly find it where the skeletons are present from last year. This is the best method. This method of examining the site for presence of a weed is called “scouting”. In this case you are scouting for a specific weed, crabgrass.

 

Q. What herbicides are used for pre-emergent crabgrass control in turfgrasses?

A. The most commonly used pre-emergent herbicide active ingredients and one of the most widely available product names associated with these active ingredients (in parentheses) in the trade are pendimethalin (Pendulum), prodiamine (Barricade), oryzalin (Surflan) and dithiopyr (Dimension). Additional trade names for these products can be found. Remember to read and follow all label directions of a pesticide. The mention of trade names does not constitute an endorsement of a product nor does the lack of listing of a trade name mean any bias or discrimination against a product.

 

Q. Is it okay to seed or sod cool-season lawns of tall fescue, Kentucky bluegrass and/or perennial ryegrass in April?

A. Response: The answer is two-fold.

1. Yes, but the spring is the distant second choice as opposed to the fall; an April seeded lawn only has the months of April and May before it starts to face non-optimal growing temperatures in most of June through the early portion of September. Seedling stands often succumb to heat, drought, disease, or insect feeding during the summer. By far the fall is a much better time, with a late September and October seeding time being preferred. Temperatures become too cold in November and December for optimal germination and establishment. Refer to OSU Fact Sheet Establishing a Lawn in Oklahoma for details.
   
   
2. It is okay to lay cool-season turf sod in April? Usually there is no problem in getting it properly established in April in time for tolerating the summer. Again, see the fact sheet referenced above.

 

Q. Is it okay to fertilize my cool-season lawn in April?

A. If you want to have a higher quality cool-season lawn, then the March-April time frame is appropriate for a fertilization. Also, the April-early May time frame is appropriate. Often, two separate applications, one in March and one in early May is suggested for optimizing cool-season lawn quality. Generally, cool-season lawns are not fertilized in late May through early September. See OSU Fact Sheet Lawn Management in Oklahoma for details on lawn fertility programs.

 

Q. Can warm-season lawns of Bermuda, Buffalo or Zoysia be fertilized in April?

A. In general, April is the first month of the year when fertilizing warm-season lawns can be suggested. Depending upon the individual year, warm-season lawns have come out of winter dormancy and are attempting to put on growth. Once the competitive winter annual weeds have been controlled, generally warm-season lawns can be fertilized in mid-April and onward until no later than September 15. Every year is slightly different with variable warming trends, rainfall, late frost, etc. See  OSU Fact Sheet Lawn Management in Oklahoma for details on lawn fertility programs.

 

Q. Can I seed a warm-season lawn in April?

A. Certainly, one can seed a lawn in April, but the real question is “How early is it advisable to seed a warm-season lawn?” Provided that one has excellent erosion control measures in place, it does not hurt the warm-season turfgrass seed to be properly seeded in the month of April. Excellent erosion control measures include but are not limited to drill seeding into stubble or other dead cover, hydro seeding/mulching, broadcast seeding followed by light raking for incorporation and mulching with either clean wheat straw, shredded mulch, spun bound polyester seed cloth or other mulch. Even though the soil may be a bit cool for germination of warm-season grass seed, the seed primes and imbibes water, meaning it takes up moisture from the soil and this starts key enzymatic processes, but the seed won’t germinate (having a root or shoot emerge from the seed) until conditions are warm enough to do so. While there is a risk of late frosts or hard freezes killing early germinating warm-season turfgrasses from seed, complete stand loss from early seeding is really rare. What is more of problem is flash hard rains (in some years) washing the soil and seed into puddles such that too low of seed amounts remain in some areas and grossly overage amounts are present where seed was puddled. So the question is not whether seeding in April is okay, but rather, if you are going to seed and wait on the seed to germinate do you have excellent erosion control measures in place to keep the seed from washing while one is waiting for it to germinate and establish? This question is important regardless of when one is planning on seeding, but more risk of seed puddling is present the longer the seed is laying in the soil waiting to germinate. Refer to OSU Fact Sheet Establishing a Lawn in Oklahoma for details.