Tips for overseeding a lawn

Over seeding new grass seed into an existing lawn is always going to prove very difficult task. This is because the new seedlings will have to compete with the established grasses and they will need all the help they can get to ensure they not only germinate, but establish successfully too.

However there are a few factors to take into consideration, and these can ultimately determine how successful your overseeding regime will be.

• Soil Compaction - Any soil or rootzone that suffers from extreme compaction will have a detrimental effect on any over seeding program. A compacted soil is a very poor environment for new seedlings to establish. Even established grasses struggle to grow on a compacted soil so what chance are new seedlings going to have? virtually none! A compacted soil will be devoid of oxygen, this will in turn lead to poor drainage, poor drought resistance, excessive thatch build, all to the detriment of your over seeding program. 

• An Excessive Thatch Layer - Thatch is the accumulation of organic matter that builds up between the grass sward and the soil. Although a little thatch is beneficial to the lawn, too much will see your over seeding program suffer. The ideal sowing depth for grass seed is usually just below the thatch layer with the seed just coming into contact with the soil. This is difficult to achieve if your lawn has an excessive layer thatch. If the grass seed is sown with in the thatch layer, it may well germinate but it will have a difficult time establishing successfully.

• The Temperature of the Soil - One of the most important factors that will have a major influence on the success of your over seeding program is the soil temperature. This is one of the key reasons many people prefer the late summer over the spring for over seeding. This is because the soil is warmer in late summer which will aid grass seed germination and establishment. That said, there is no problem with over seeding during the spring, however the results maybe inconsistent and in some cases disappointing. In recent years we have experienced cold springs with overnight frosts, which havent been great for over seeding, often yielding very poor results.

• Irrigation and watering - The amount of water the lawn receives following overseeding will also play a part in the germination of the seed. All new seed requires water to establish successfully. However getting the balance right is important, apply just enough to maintain adequate soil moisture.

• Mechanical operations prior to over seeding - Carrying out key lawn maintenance tasks such as aeration or scarification and raking prior to overseeding will be very beneficial in helping the seed to germinate and establish successfully. These operations help open up the surface of the lawn creating a seed bed where the seed comes into contact with the rootzone.  This will help promote both good germination and establishment of the seed.