What Is Aeration?
Technically speaking, aeration is the naturally occurring process of air exchange between the soil and its surrounding atmosphere. Practically speaking, aeration is the process of mechanically removing small plugs of thatch and soil from the lawn to improve natural soil aeration. It’s commonly called “core aeration” in the lawn service industry, and you may have heard of it as soil cultivation (coring, spiking and slicing). Most homeowners simply call it aeration.
Core aeration can help make your lawn healthier and reduce its maintenance requirements through these means:
- Improved air exchange between the soil and atmosphere.
- Enhanced soil water uptake.
- Improved fertilizer uptake and use.
- Reduced water runoff and puddling.
- Stronger turfgrass roots.
- Reduced soil compaction.
- Enhanced heat and drought stress tolerance.
- Improved resiliency and cushioning.
- Enhanced thatch breakdown.
How Often Should You Aerate A Lawn?
Most lawns benefit from annual aeration. Heavily used lawns, or those growing on heavy clay or subsoils may need more than one aeration each year. Again, turf responds best when tine spacing is closer and penetration is deeper.
When Is The Best Time To Aerate Lawns?
If you have cool season turfgrass such as Kentucky bluegrass and perennial ryegrass, both spring and fall are ideal times to aerate. In spring, aerate between March and May. Perform fall aeration between August and November. Aeration before or at the time of late season fertilization enhances root growth and improves spring green-up and growth. Warm season turfgrasses such as zoysia grass and Bermuda grass should be aerated in mid-spring to summer. Avoid aerating when warm season grasses are dormant – it may encourage weed competition. In addition, avoid aerating warm season grasses during spring greenup, and not until after their first spring mowing.
What Can You Expect?
Immediately after aeration, your lawn will be dotted with small plugs pulled from the soil. Within a week or two, they break apart and disappear into the lawn.
About 7 to 10 days after aeration, the aerification holes will be filled with white, actively growing roots – a sign that the turfgrass is receiving additional oxygen, moisture and nutrients from the soil.
On compacted soils and on lawns with slopes, you should see an immediate difference in water puddling and runoff after irrigation or rainfall. After aeration, your lawn should be able to go longer between waterings, without showing signs of wilt. With repeat aerations over time, your lawn will show enhanced heat and drought stress tolerance. Remember, most lawns benefit from annual aeration. And while you shouldn’t expect miracles, especially with poor soil, lawns that receive this care will be healthier, more vigorous, easier to maintain and have fewer pest problems.
Aeration Equipment Affects The Outcome...
The type of aeration equipment can determine how effective the treatment will be. In general, turf responds best when core holes are close and deep. Equipment with hollow tines removes soil cores. Equipment with open tines divots the soil surface. Aeration equipment also varies in tine size up to 3/4 inch diameter and in depth of penetration up to 4 inches, depending on the manufacturer’s specifications.
What is Turf Seeding?
Overseeding is the planting of grass seed directly into existing turf, without tearing up the turf, or the soil. It’s an easy way to fill in bare spots, improve the density of turf, establish improved grass varieties and enhance your lawn’s color.
If a lawn looks old, or just “worn out,” if it needs growing amounts of water and fertilizer to thrive, or is disease or insect prone, it’s a perfect candidate for overseeding.
Reasons To Overseed:
- Fill in bare spots
- Improve turf density and color
- Helps lawn withstand insects, disease, drought, shady conditions, and heavy traffic
- Reduce the amount of fertilizer, water, and pesticides required
Before You Overseed
For various reasons, old turf sometimes deteriorates dramatically or dies out completely. Overseeding with an improved grass seed mixture can get new turf growing in bare areas as well as “sprucing up” areas where the turf is thin and unhealthy looking.
First, however, you must analyze the problems that caused the original turf to deteriorate. It might be due to conditions that, if not corrected, will eventually cause the overseeded lawn to deteriorate, too.
Correctable problems include:
- Poor soil condition
- Improper drainage
- Soil compaction
- Insufficient water
- Poor fertility
- Poor air circulation
- Insufficient sunlight
- Excess thatch
- Grass varieties not suitable for the area
- General neglect
If you have trouble identifying the problem, ask your local lawn professional or your county extension office. The main thing is to correct the problem before you establish new grass.
When is the Best Time to Overseed?
Late summer or early fall is the best time to overseed lawns. Soil and atmospheric temperatures are most favorable for optimum seed germination and growth. With adequate moisture, fertilizer and sunlight, the new seedlings will be well established before cooler fall weather sets in. Also, weed competition is less of a factor at this time, giving the grass seedlings a better environment to grow and develop.
Spring overseeding risks the chance of weather-related problems (heavy spring rains, unexpected high temperatures) and weed competition. Also, spring seeding may interfere with the application of preemergent crabgrass or broadleaf weed killers; concurrent application of seed and herbicides is generally not recommended because the herbicides may cause poor seedling establishment. It is best to delay herbicide treatment 4-6 weeks after new grass seed germinates. If you choose to overseed in the spring, be sure to follow proper seeding and treatment practices.
Midsummer overseeding faces greater chances of disease, heat and drought stress, and weed competition. Proper weed control and adequate irrigation are musts if overseeding is attempted in midsummer.
What About Care After Overseeding?
Depending on conditions and type of seed, new grass seed will begin to emerge in 5-7 days after seeding when moisture and soil temperatures are adequate. An overseeded lawn can be fully established in eight weeks or less.
Proper watering is critical to successful overseeding. The following is a recommended watering program.
- Immediately after overseeding: Water heavily to wash grass seeds into slits.
- Until grass seeds germinate (first 10-14 days): Water lightly on a daily basis, soaking first one inch of soil.
- After germination: Water less frequently, but allow for deeper soaking and penetration into soil. This encourages deeper root growth.
- After grass becomes established: Water at the recommended level for the type of grass planted.
The key is care and patience. Proper overseeding will produce a healthier, better looking lawn that responds better to mowing, fertilizing and watering. An added benefit is increased property value!
Professional Seeder Features
Some features to consider in a professional seeder are:
- Look for units with a raised seed box. If a seed box sets too low to the ground, moisture on the grass when seeding early in the day can cause seed in the hopper to clump or clog the hopper opening. Look for a seed box that sets higher up on the unit to help eliminate seed clumping.
- Look for a seed box with a clear lid so you can see when you are running out of seed in the hopper and can avoid dry walking.
- The main blade shaft is the primary moving part on a seeder and will ultimately put strain on the bearings that are on either side of the shaft. Greasable cast iron bearings last longer, offer less down time, and require little maintenance.
- Look for a seeder that is versatile for additional turf renovation applications. Some units can be converted from a seeder, to a vertical cutter, or dethatcher in minutes.
Do You Need to Start Over?
Proper overseeding can renovate a lawn if it has at least 50% or more healthy turf. However, if your lawn has less than 50% healthy turf, it may be better to kill out the old turf, weeds, etc., and reseed the entire lawn.
What is Thatch?
Thatch is a communion of dead grass, roots and other matter that builds up in grass over time. It’s very common and collects on most lawns at some time or another. Thatch collects above the soil at surface level and becomes intertwined in grass stems. When the cycle of decomposition is delayed for any variety of reasons, dead matter will begin to build up. As the build up increases the matter becomes stacked and then packs down or mattes, causing healthy grass blades to become stressed and weaken.
Left untreated, thatch can literally choke a lawn to death. As thatch thickens it robs the soil of air and hinders water absorption and nutrient penetration to the soil and root system. Not only will excessive thatch kill the grass, left undeterred long enough it will damage the soil so that even if removed, new growth in that area will be sparse at best without soil treatment. Thick thatch levels can also become a haven for insects. Moisture rich matted thatch can be an excellent breeding ground for mosquitos and disease. Knowing the level of thatch you have will assist you in the best way to combat the problem properly.
How Often to Dethatch?
Dethatching can be performed any time during the year outside of drought or frost. Don’t wait for the fall to perform a dethatching treatment at a moderate or excessive level of thatch unless you are in a prolonged season of drought.
What to Expect After Dethatching?
Most people are shocked to see how much thatch even a healthy lawn can collect in a single growing season. Lifting the thatch to the surface is just the first step. After the lawn is dethatched, the thatch must be removed from the top of the grass or it will mat back down to the soil surface. You can use a hand rake or blower to pile the thatch for bagging or you can use a lawn/leaf vacuum for quick clearing.
Annual maintenance dethatching (thinning thatch a ¼ inch in depth or less performed with a spring tine blade dethatcher) should leave no noticeable damage to the lawn. Actually it is likely that you will find that your grass has greened up a little over the next week or so due to increased exposure to air and water.
Moderate thatch dethatching may expose thinning areas and bald spots caused by soil compaction. An overseeding treatment followed by fertilizer will spruce these areas up in 2-3 weeks if performed in season. If performed late in the fall, you should notice a much thicker lawn will grow in the spring.
Excessive thatch treatment is more intrusive to the lawn and the soil. After a dethatching and aeration treatment, you may notice bald spots and core holes in the soil. These holes are needed to help the soil and existing grass root system strengthen and recover, however you should wait at least 7 – 10 days before an overseeding treatment to allow the soil some time to recover.
Thatch creates a water barrier, prevents new grass from growing and harbors insects. It collects quickly and before long the lawn and its entire root system is at risk. Lawn dethatching, when performed as needed, will go a long way in maintaining a healthy, green lawn.
Equipment Makes a Difference
Dethatchers are powered rakes. Also commonly known as turf rakes or power rakes. They grapple at the soil surface lifting dead matter to the top of the lawn so it can be removed. Walk-behind turf rakes utilize spring tines (pliable) or straight blades (hardened steel) to lift and/or slice through thatch.
Multi-purpose blades: Deep slicing blades for thatch a 1/2” or deeper. Ideal for harder soils. Commonly the standard blade real on overseeders where deeper soil slicing is necessary. The unique design of the blades, with a cutting edge on both ends, doubles the blade life.
Vertical slicer blades: Sharpened on both sides, designed to slice through surface root grasses like Bermudagrass. Also exceptional for use as an aerator for sandy soil grasses.
Flail blades: Common standard blade used to treat moderate thatch levels. Ideal for deep rooted grasses. Blades both lift thatch and thinly slice soil surface.
Spring tines: Ideal for annual thin to moderate thatch control. Pliable tines gently rake through the grass without slicing the soil or causing damage to above ground implements like sprinkler heads.
Note: Only use vertical slicer blade dethatchers on surface root grasses like Bermudagrass.
This thin layer of thatch also aids in cooling the soil surface during the harsh sun and the heat of summer. That being said, this layer should be thinned out with a dethatching treatment in the fall or before the first frost of winter. Look for a unit with spring tines for gentle raking.