Crop and Soil Environmental News, September 2008
Author: Mike Goatley, Extension Turfgrass Specialist, Virginia Tech
Following an extended summer drought, fall rains provide a very quick distinction between living and dead cool-season turf. Turfgrasses will quickly resume the expansion and emergence of previously formed leaves that were shut down by the drought and will also initiate new leaf growth that will contribute to an overall greening of the turf within a day or so of a significant rainfall event. If the turf does not show signs of recovery, then make preparations for renovating the turf in the fall, the best season to establish cool-season grasses.
If the entire lawn has failed, then complete renovation involving an application of a non-selective herbicide such as glyphosate to control all the existing vegetation is often appropriate. At this time, you have the opportunity to consider if perhaps another cool-season turf might be better suited to your needs and climate. Tall fescue works well across much of the state and research at the Hampton Roads research station is showing that a mix of tall fescue and hybrid bluegrass has desirable qualities. If tall fescue repeatedly fails, then perhaps it is time to convert to one of the improved, cold tolerant varieties of zoysiagrass or bermudagrass next summer. Complete renovation is costly, very labor-intensive and often is not required. Most lawns will likely have problem spots measuring anywhere from 50 to 150 sq feet and these spots will be surrounded by healthy, great looking grass, so it makes sense to concentrate only on the small areas.
No matter the level of renovation, be sure to conduct a soil test if one has not been made within the past 3 years. Your local extension office can help you with the materials and proper steps to follow in soil testing. And when choosing the grass for spot renovations, try to select grasses with similar appearance and growth habit as to the current lawn in order to maintain turf uniformity. The final pre-plant step is to properly prepare the soil for planting. Some degree of soil preparation is essential for successful turfgrass establishment; there is a name for simply sprinkling seed over top of an unprepared soil: expensive bird food! Consider making multiple passes with a core aerator or a power rake/dethatcher. Do-it-yourselfers can often reserve these machines or specialized power seeders at rental stores, and consider that area lawn care professionals very likely have both the equipment and expertise to deliver successful turf renovation.
What about how much seed to plant? While there are well defined seeding recommendations for new plantings available in information from your local Virginia Cooperative Extension office, this is a tough question to answer for spot renovations. If there is an area of 500-1000 sq ft that needs repair, then weighing out the appropriate amount of seed (it might range from 1 to 8 pounds depending on the grass selected) and applying it with a rotary or drop spreader over the area is fairly simple. However, for only a few problem spots in a lawn, the last thing one needs is a 50 lb bag of seed, so this is where smaller packages of seed become more cost effective. Let’s consider what NOT to do in order to handle spot renovations correctly: visibly seeing 1 seed every sq inch is NOT enough, but at the same time, seed stacked upon seed so thick that you can not see the soil is even worse! It is not an absolute number by any means because seed size among species is highly variable, but for most grasses somewhere between 10-15 seed per square inch corresponds fairly well with recommended planting rates for new establishments. Competition among germinating seedlings that are seeded too densely will end up controlling most (if not all) of these plants, so this is another case of too much is not a good thing.
Another valuable tool in partial renovations is a compost application. The compost can be applied either before or during the soil preparation procedures or as a topdressing following seeding. For topdressing, only 1/4 to 1/2 inch depth of a quality compost is required. Then, success can be enhanced further by lightly mulching the seeded areas to help conserve moisture, reduce seed movement from rain/irrigation events, and further enhance establishment. Wheat straw works great with about 1 bale/1000 sq ft of area being an appropriate mulching density. The key to the right amount of mulch is that you should still be able to see some of the soil underneath the straw. An advantage to straw mulch is that you don’t have to worry about picking it up after germination is complete. Simply mow the turf when it needs to be clipped and chop the straw right back into the turf canopy. There also are bagged mulch products made from recycled newspapers available at lawn and garden centers. Many of these products also contain seed and fertilizer and these specialty products are particularly handy for very small renovation areas. Just be sure that you are matching up your turfgrasses when you use these products. After mulch is applied, initiate light and frequent irrigation to optimize establishment, and as the turf matures, reduce the irrigation frequency and amount.
Also, don’t forget the exceptional value of sod for spot renovations. Sod can be cut and shaped into various sized patches and the improvement in lawn appearance is essentially immediate. Soil preparation for sod installation is best handled by light tillage and smoothing of the surface prior to installation. Sod is more forgiving in water requirement and frequency than seeding establishments and provides a turf that can handle limited foot traffic almost immediately. Rolling it after installation to maximize sod/soil contact and smooth the surface with the existing grass further enhances both its appearance and chance for long-term establishment success.
Follow these steps this fall to return your lawn into not only a thing of beauty, but also one of Mother Nature’s most effective means of water filtration and soil stabilization. Remember that your local Virginia Cooperative Extension office offers plenty of resources and expertise in your quest to keep the lawn green and our water clean.
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