Spring lawn seedings

By John Fulton

[March 17, 2011]  Warmer temperatures have us thinking spring. Lawns are greening up very quickly. Spring seeding of lawns is usually our second-best choice, because of the warm weather soon to follow, but it does work when we have cool, wet weather. Fall has been the preferred time for many years, but once again, temperature and moisture have a great effect on success.

Spring seeding should be done between March 15 and April 1 for the best chance of success. The reasons for the early date are the heat and the long germination time for Kentucky bluegrass. It can take up to a month for bluegrass seed to germinate. This means an April 1 seeding might germinate May 1. Then add six to eight weeks for it to become established. This could then be close to July 1. Usually we tend to get hot weather by then.

Let's start with the basics. The normal seedings are a blend of Kentucky bluegrass, perennial ryegrass and fine fescue. The fine fescue is much better in shade, and the perennial ryegrass will provide quicker cover. The seeding rate is generally 4 pounds per 1,000 square feet in bare dirt seedings. Use 2 pounds per 1,000 square feet in overseeding thin lawns. Of course this can run into some real money when doing very large areas. Many rural seedings are done more on the basis of a pound per 1,000 square feet. An acre is almost 44,000 square feet, so you can do the math on this one.

Fertilizer is always an area of many questions. The place to start is a soil test. This will tell you what you are starting from. Basic soil test levels for phosphorus, potassium and soil pH should be in the neighborhood of 40, 350 and 6.1, respectively. Phosphorus and potassium are on a pound-per-acre basis. This must be considered if you use labs that report in parts per million, which will give numbers half as large. These numbers will provide a great environment for grass.

Grass will grow in very poor conditions, but it certainly won't have that manicured look many strive for. Lacking a soil test, or being at recommended fertility levels, general maintenance applications provide a pound each of nitrogen, phosphorus and potassium per 1,000 square feet of lawn area in May and again in September. Really lush lawns will usually have twice as much nitrogen applied in a season but split among four applications.

If you decide to try seeding this spring, remember a couple of things related to weed killers. First, you can't use crabgrass preventer in the spring if you put down seed. The crabgrass preventer doesn't know the difference between grass seed and weed seeds. The second rule is to mow the new seeding at least three times before trying any broadleaf weed killer. Generally this means spring broadleaf control doesn't happen when you seed in the spring.

The end result is if you seed in the spring, you control weeds in the fall. Seed in the fall, and you control weeds and crabgrass in the spring. If you do plan to use a crabgrass preventer, time it so it is on about the time the forsythia blooms. This would be the approximate soil and air temperature needed for the crabgrass to germinate. April 1 is a good guess, but this date can vary widely with the weather. Also, many crabgrass preventers last for only four to eight weeks, so plan on repeating the application in June anyway.

One last item for the week. Many lawns have brown spots or patches. In most cases these are a warm-season perennial grass such as nimblewill. There is no selective control for these grasses, meaning glyphosate (Roundup). These spots green up slowly and brown out early. The best plan is to spray them in late July when they are growing, then put down new seed in mid-August.

To-do list

Watch roses to determine when to start uncovering and pruning. Many recommend doing your pruning chores when forsythia is in bloom.

Also, if you haven't uncovered strawberries, keep an eye on them. They should be uncovered when you see green leaves under the straw and definitely when you see yellow material -- that means you are just a little late. Keep the straw handy in case you need to re-cover them.

[By JOHN FULTON, University of Illinois Extension]