Turf Overseeding

Cool-Season Grasses

Is your lawn composed of cool season grasses? If so, it may well take a beating from the heat to which it is subjected in summer. After all, by definition, cool-season grasses crave the cooler temperatures of spring and autumn. But there's something you can do to undo summer's assault. It's called "overseeding lawns" "Overseeding lawns" is just what it sounds like. Namely, you're sowing seed over existing grass, in order to fill in the bare patches. Therefore, overseeding lawns makes sense only if the existing grass is healthy enough and abundant enough to be worth keeping. If you currently have only 50% coverage, then you need to tear up the old lawn and start a new lawn from seed.

Preparations for Overseeding Lawns

Another step to take to promote contact between seeds and soil is core aeration, or "lawn aeration." This step will help reduce lawn thatch, which stands in the way between grass seeds and the soil they'd like to call home. In severe cases, you may need to add a layer of topsoil before overseeding lawns. For instance, due to shallow tree roots popping up on the lawn, your topsoil layer may be too thin. Spread 1/4" of screened topsoil over such an area, and rake it in.

Overseeding Lawns

The recommended rate for overseeding lawns is 4-5 pounds for every 1000 square feet that you need to cover.  For the proper operation of overseeding lawns, use a spreader. Set the spreader to the recommended overseeding rate. At the same time, apply a starter fertilizer for better results. The grass seeds must be watered properly, in order to germinate. Use just a fine spray, as you don't want to create a flood! The soil should be kept evenly moist, which may mean several waterings per day (depending on the weather), for several weeks. After the grass blades sprout, you'll still need to water a couple of times per day. If you know your schedule won't permit this, the time to look into automatic irrigation system is before overseeding lawns, not after.

The best time for overseeding lawns that have cool-season grasses is in September; the second-best time for overseeding lawns is in March or April.

Shaded Lawns - Best Lawn Care and Treatments Advice

Shaded lawns have different requirements from lawns that are grown in full sunlight. A shaded lawn may be in full sun for part of the day and full shade for the rest of the day or it may receive filtered sunlight that passes through the canopy of the trees and leaves.

Stress Effects of Shade on the Lawn

• Shaded lawns are subject to more stress than lawns that are grown in full sunlight. Reduced sunlight can be caused by the shading effect of trees, shrubs and buildings. Fallen leaves can also shade a lawn and prevent sunlight from reaching the grass blades.
• The first signs of stress is usually a result of less sunlight. Specifically, the amount of photosynthesis that takes place in the grass is greatly reduced. Photosynthesis uses the energy of sunlight to produce 'food' for the grass so that it can grow. In shaded lawns the rate of growth is therefore slower when compared to sunny lawns.
• A side effect of limited sunlight is that it results in the lawn being more subject to moss infestation as the turf is holding more moisture due to the lack of the suns drying effect. Moss thrives in damp conditions.
• The other main stresses on the lawn are caused by the roots of trees and shrubs which overhang the lawn. The roots of these trees and shrubs compete with the grass for both water and nutrients. Large trees can lose hundreds of litres of water a day by evaporation through their leaves. They replace this water by drawing it up from the soil and through their roots. The trees root system can deprive the grass roots from being able to take up sufficient water.
  Trees can also prevent rain from reaching the lawn and soil as it can be intercepted by their leaves and branches and then lost through evaporation. Trees and shrubs also take up nutrients from the soil and so the lawn suffers because there are fewer nutrients that are available to the grass roots.
• The net effect of these extra stresses on the shaded lawn mean that it has slower growth rates, is more susceptible to drought and requires a longer recovery and re growth period after mowing.
• All lawns need some degree of sunlight for sufficient growth and if this level of sunlight is not available then the lawn will not grow properly and it will be impossible to establish / maintain the lawn. If this is the case then an alternative ground cover plant should be considered along with other alternatives such as bark mulch, synthetic turf and gravel.

Actions to counteract the stresses faced by a shaded lawn

Overseeding

• Choose suitable grass type(s),
• Certain grasses are much more shade tolerant than others. Fescues are commonly used on shaded lawns, especially red a chewing fescue.
• Water thoroughly (roughly once a week in the hottest parts of the year).
• Mow higher than lawns that receive full sunshine
• Only remove 1/3 of the grass height when mowing
• Prune trees and shrubs – reducing the shade level. Raise the tree's canopy to 8 feet by removing the lower branches. Thin the density of the trees canopy by selective pruning to enable more light to filter through the spaces in the canopy. 


Starter fertilizer benefits 

• Starter fertilizers are a small amount of fertilizer applied to the soil to meet the demands of the seedling for readily available nutrients until the plant’s root system develops. They also enhance the development of the emerging seedling. 
• Phosphorus (P) is the key nutrient components in a starter fertilizer. Phosphorus is non-mobile in the soil, thus, undeveloped seedling roots have difficulty obtaining the necessary amounts for proper growth. Therefore, added phosphorus promotes vigorous root growth.

How Starter Fertilizer Affects Plant Growth

The use of starter fertilizer enhances seed growth primarily because it places a readily available supply of plant nutrients (especially phosphorus) in a position where they are easily accessible to the limited root system of a seedling. Even though a soil may have high fertility, a seedling’s root system may not be able to obtain the necessary nutrients due to lack of size and density within the soil. Once a plant’s root system is established, it will be able to extract nutrients from the bulk of the soil. At this point, the soil serves as the primary source of plant nutrients. Since the plant now has a well-developed and extensive root system, it has more surface area to intercept nutrients and moisture throughout the soil.

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