What is overseeding
Overseeding an already established lawn is regarded by many lawn experts as an essential task in the autumn maintenance program. Overseeding is the process of sowing new grass seed into lawn.
Why overseed a lawn
Turf can be overseeded for various reasons, which include:
- To repair any weak or thin areas on the lawn caused by the stresses of the summer months. Grass coverage can suffer during times of drought, constant close mowing and following weed control. Whatever the reason, overseeding during favorable conditions will help return the lawn back tip top condition with full grass coverage.
- To help the lawn recover from scarification or raking. Turf is regularly scarified to remove dead moss or thatch and this often leaves the lawn looking ragged and thin afterwards. Overseeding enables the sward to recover quickly, as the the new seedlings establish and thicken up the weak areas.
- Improve the turf characteristics. Turf health is often influenced by varying ground, weather conditions etc. E.g. Extended periods of hot, dry weather (drought), excessive rainfall resulting in constant waterlogging or buildings and vegetation causing shade problems. Overseeding with a suitable grass seed mixture can help the lawn perform better in these situations.
- Overseeding can also be employed to create resilient turf that will withstand wear and tear, which is great if you have children or the lawn receives alot of traffic.
- When used in conjunction with other turf care practices such as aeration, scarifying and top dressing, overseeding plays a major role in creating a luxury lawn, often desired by many keen gardeners.
One of the problems gardeners face with overseeding, is the new seedlings have to compete with the established grasses. Turf professionals have the luxury of Plant Growth Regulators when they overseed. A growth regulator is used to suppress grass growth, which is beneficial prior to overseeding.
This helps the new seedlings germinate and establish more successfully, as competition from the established sward is greatly reduced. However these growth regulators are not available for amateur gardeners, so they have to get by with out them.
In order to achieve optimum results this task should be carried out when conditions are favorable for seed germination. This is when the soil is warm and moist, typically associated with late summer / early autumn. In some cases (following agressive moss control and removal) a lawn may require seeding during early spring, to help thicken up the sward prior to the onset of summer.
Although overseeding during the spring is fine, success is often influenced by the soil temperature. Many times during spring we get a couple of warm weeks, only for it to turn cold again. When this happens new seedlings can take time before they establish properly.
During autumn the soil will be at it warmest as it has all summer to warm up. The only drawback is the soil may be dry, but this can be rectified by giving the lawn a good soaking prior to overseeding.
Another reason why autumn is preferred over spring is there is likely to be less disruption on the lawn following overseeding. Grass seed sown in the spring may have to deal with drought, close mowing, wear and tear and chemicals used for controlling weeds.
When overseeding is undertaken in the autumn it is near the end of the growing season. This means less disruption and stress on the new seedlings, giving them a better chance of establishment.
Autumn lawn renovation program
The chances of the seed germinating and establishing are greatly improved when overseeding is undertaken following aeration and scarification and prior to top dressing. All three along with overseeding should be included in a typical autumn renovation program.
- Aeration relieves soil compaction by puching holes into the surface of the lawn. This helps bring the grass seed into contact with the soil, which improves the chances of germination. It also encourages the newly germinated seedlings to develop a strong root system.
- Scarification removes thatch and dead moss from the lawn with is series of vertical blades or tines that slash into the base of the turf to remove the debris. This leaves grooves in the surface, which creates a perfect seed bed prior to sowing the seed.
- A lawn top dressing should be applied following scarification, aeration and overseeding. Some turf care experts recommend the grass seed being mixed with the top dressing, either way should produce good results.
How to overseed a lawn
As we previous touched upon overseeding should be undertaken following aeration and scarification, when the soil is moist.
Mow the lawn prior to applying the seed, mow it a little shorter than you normally would, but avoid scalping or stressing the grass. This will encourage the seed to work its way into the sward and make contact with the soil.
Disperse the grass seed evenly over the lawn, ideally when the surface of the lawn is dry. This can be done by hand or with a spreader. If sowing by hand it can be applied in two directions, each at half rate. The second pass should be at 90 degrees from the initial pass.
The seed should be applied at the manufacturers recommended rate, this is usually between 10 – 25 g/m depending on which grass species you are sowing.
The seed then requires working into the sward, aeration holes or scarification grooves. A dragmat, tru-lute, besom brush or the topside of a flat backed rake can be used to accomplish this. If top dressing is going to be applied then the seed can be brushed in with the top dressing.
If the lawn requires a seasonal feed now the time to apply it, if it hasn’t already been applied. All that’s left to do now is ensure the soil is kept moist to help germination.
It is also a good idea to raise the cutting height of the mower and ensure the blades are sharp. Blunt mower blades can damage new seedlings.