Green Industry Resources
Hort Update- Seasonal Information for the Green Industry
Spring is a great time to repair a thin or damaged lawn. But before overseeding, it's a good idea to evaluate the turf and determine why the grass is performing poorly. Diseases, insects, excessive shade, drought, salt damage, soil compaction and many other factors can damage a lawn. Understanding what happened to the turf is an important step in determining a solution to the problem. For example, shady areas should be planted with shade tolerant grasses like the fine fescues (creeping red fescue, hard fescue and sheep fescue) or shade tolerant Kentucky bluegrass cultivars. Compacted areas should be aerated and planted with a grass blend that includes perennial ryegrass, the grass most tolerant of compacted soils. Aeration done on a yearly basis will also help relieve soil compaction. Insect, disease and drought problems can be lessened by using endophyte-enhanced turfgrasses, including cultivars of tall fescue, fine fescue and perennial ryegrass. Using disease resistant grass cultivars is also important to control common disease problems like Brown Patch in tall fescue.
Choosing the right grass for your soil and environmental conditions, and purchasing a high quality, certified seed blend is half the battle in establishing a healthy turf. Remember- scrimping on the quality of the seed will soon be evident in the quality of turf. Seed that is certified by the Nebraska Crop Improvement Association is usually identified with a blue tag on the seed bag. A good grass blend should include 3-4 different species or cultivars of grass. Check the seed label and avoid seed blends that include coarse textured, pasture grasses like K-31 tall fescue or annual grasses like annual bluegrass or annual ryegrass.
Spring overseeding of Kentucky bluegrass should be done from April 1st to April 30th; tall fescue- between April 15th and June 15th. The amount, or rate, of seed applied in an overseeding operation differs compared to that used for a new seeding. Kentucky bluegrass should be applied at 1-2 lbs. per 1,000 sq.ft. and tall fescue at 4-6 lbs. of seed per 1,000 sq.ft. When working with small amounts of seed, mix sawdust, dry sand, organic fertilizer, or any other suitable material with the seed to aid in obtaining uniform coverage.
Before spreading the seed, prepare the soil to create a good seedbed. Small areas can be prepared by hand raking to remove excess dead top growth and loosen the soil surface. Larger areas can be prepared by aerating or power raking. Aerating opens up the soil and provides a good surface for seed germination. Seeds that fall into the aeration holes will germinate and grow well; there is no need to topdress or fill in the holes before seeding. Power raking should be used only if a thatch layer in excess of 1/2" is present.
Applying a pre-emergent herbicide for weed control is especially important with spring seedings since weed pressure is so much greater early in the year. The only pre-emergent herbicide that can be used with new seedings is Siduron, commonly sold as Tupersan. This herbicide will provide good control of annual grassy weeds like crabgrass and foxtail, yet still allow the grass seed to germinate. For new seedings, use the lower recommended rate and repeat the application one month later.
Finally, keep the new seeding moist until germination has occurred, then gradually decrease the amount of water applied. Kentucky bluegrass should receive 1" of water during spring and fall, and 1.5" of water in mid-summer. Tall fescue is drought tolerant and once established can be grown in most years without irrigation. No matter what type of grass is used in the turf, apply water deeply and infrequently to encourage deep rooting. Sharpen the mower blade before cutting the new stand of grass to avoid tearing out the new plants and reduce the probability of disease infection.