Understanding Seed Germination

In order to germinate, turf grass seed must have the following:

Water is important for several reasons. As the seed absorbs water, the seed coat ruptures and the shoot and primary root emerge. Water also allows the movement of oxygen into the seed. In addition, water makes possible the transfer of food to the shoot and the root and if the availability of water is interrupted after this process has begun, the seedling grass plants may die. That's why it is so important to keep a new turf area continually moist until its root system is sufficiently developed to extract the water from the soil.

Although there are minimum, maximum and optimum temperatures for the germination of all turf grass varieties, most seed germinates best when subjected to the natural alternation between day and night temperatures. Kentucky bluegrass, creeping bentgrass, ryegrass and tall fescue germinate when exposed to temperatures alternating between 60 and 85 F., while warm season grasses such as bermudagrass and buffalograss prefer a warm 70 to 95 F. range.

Oxygen is essential during germination because the rate of respiration, a process with a high oxygen demand, increases rapidly in germinating seeds. Compacted soil conditions caused by traffic or saturated soils will reduce seed germination by restricting or eliminating oxygen.

Exposure to light promotes germination of some grass seeds, including Kentucky bluegrass, bermudagrass, Poa trivialis, hard fescue and chewing fescue.

Comments on Spring Seeding

Some lawns have not fully recovered from damage that occurred last year. As a result, many homeowners are considering seeding this spring.

In our area, fall seeding is much preferred over spring planting, especially on open, sunny lawns. Spring seeding is not as risky on shady lawns. If a small sunny area of the lawn is severely damaged, spot sodding this spring would be the most effective repair method. If the entire lawn is thin, proper fertilization, watering and mowing, will promote spreading and thickening of the existing turf.

If possible, we recommend that seeding be delayed until fall.

If you do decide to seed this spring, there are several factors to consider. Dethatching may be necessary prior to planting. Any seedbed preparation will stimulate weed growth during the spring and summer. Effective weed control agents cannot be applied until the new grass is tall enough to be mowed several times. Because of this time delay, it will be almost impossible to control crabgrass and other grassy weeds this summer. As a result, the planted area may resemble a weed patch by the middle of July! If the area is kept watered, the new grass may survive and this fall, when the weeds die out, a decent stand of grass may remain. Should this summer be severe, the young, immature grass plants may be killed by the heat, despite adequate watering.

Remember to mow the grass at three inches.

In any case, there is a good chance that additional seeding will be necessary in the fall!
Our approach is to do the best we can with the damaged turf and make our seeding decisions in the fall.