Optimal Blade Height: The Secret To Tall Fescue Overseeding Success

I’ll admit I was a bit of a Joker when I first began overseeding my lawn. I would ridiculously throw seed on the lawn in the evening after a quick mow. If I was feeling particularly bold I’d toss some compost down after and call it a day.

I suppose it got the job done but, likely very inefficiently. Then I discovered the secret: Cutting my grass shorter. This exposed more ground so the seed didn’t have to compete with already established grass.

But just how short should you cut tall fescue before overseeding?

Cut Tall Fescue to a height of 1-1.5 Inches in early fall before overseeding. This exposes more soil and creates an environment for new seedlings to compete with existing grass.

Now, if you don’t want to make the same mistakes I did when I first started overseeding my lawn, you better keep reading and your lawn will look far better than my lawn ever did.

Gradually Lower Your Mower Height

If you lower your mower height to 1.5 inches after previously mowing at a height of 3.5 inches it could potentially shock your grass through a process known as scalping.

This isn’t a particularly bad thing to do when overseeding, but it may stress out your mower and be extremely frustrating when using an electric mower in particular. (I’ve gotten my mower bogged down in grass more than once.)

This is why it’s best to lower the mower gradually over a few mower passes. You could do this in one day or over several depending on how quickly you want it finished.

Don’t wait more than a week, since tall fescue can grow an inch per week in spring and fall.

Mowing Height on Grass Health and Recovery

You never want to cut too much of tall fescues blades about one third is optimal for every mow. This keeps the grass healthy. The reason scalping your grass during overseeding is optimal is because it allows your new seed to compete.

Weeds may find an opportunity to invade a weakened lawn, but as long as your fresh seed takes root quickly it should be able to outcompete the weed seeds and begin to match your overall lawn.

Its also best to overseed in early fall because you can mow shorter when your lawn is less stressed from the heat.

Tall Fescue Growth Patterns and Varieties

The ideal time of year for overseeding is based on climate. Here in California where I live its best to overseed in the early fall when it begins to cool down and the grass is less stressed from heat. This along with lowering your mowing height makes it the ideal time to overseed.

Make sure to assess the condition of the existing tall fescue, including its thickness, health, and weed presence. During this time you should amend the soil and prepare the area for overseeding. Our guide on keeping your tall fescue looking lush reviews our top 7 best fertilizers.

Best Tall Fescue Seed Varieties

Depending on where you live and what your goals are, there may be a better tall fescue variety for you.

  • Turf-type tall Fescue: This is probably best for more southern states and even in California where I live. Unfortunately normal tall fescue is sold at my stores and I need to search for turf type elsewhere.
  • Tall Fescue: This is the most common course blade type that prefers cooler weather.
  • Dwarf tall fescue: This is a shorter type of tall fescue that can be mowed at a much lower height of 1.5 to 3 inches.

If your interested in Dwarf tall fescue its commonly labeled low grow fescue seed mix.

Best Seed Type to Mix with Tall Fescue

Kentucky Bluegrass is the best seed to blend with tall fescue. Unfortunately its not the best for many climates. Hotter climates and drought prone regions are not the best locations for Kentucky bluegrass to be planted.

Many in more drought prone regions mix Bermuda and tall fescue grass. This allows for a greener heat tolerant grass in the summer and a cooler grass to thrive in the winter.

While I don’t condone mixing either grass it may be a fine project if you want to add variety to your lawn throughout the year.

Prepping the Lawn For Overseeding

When it’s time to begin overseeding it’s important to change your mowing routine. You will need to remove any grass clippings and dethatch or aerate your lawn.

I typically dethatch my lawn with a rake and then sweep up the loose pieces and toss it into my compost bin.

Aerating your lawn is a little bit trickier, but you can also smooth out your lawn with some compost mixed with sand to level out your lawn and make it easier for new seed to take root.

This will allow an even spread of seed that won’t need to compete with organic material that has not yet broken down. Remember to keep the lawn moist and water the newly overseeded lawn as needed to retain that moisture.

lawn recovery and maintenance

The best time to mow after overseeding is at about 2-4 weeks or when seedlings have reached a height of 3-4 inches.

This is because the seedlings need to set proper roots to withstand the mowing. This is also why it’s best to overseed in the early fall when grass growth begins to slow down and roots have a better chance of establishing.

Your mower moving into the winter should be set a bit lower at 3 inches instead of 4. The hot summer days won’t wreak havoc on your lawn and watering won’t need to be as intense.

Treating Fungus Related Issues

Since you’re keeping your grass as moist as possible to allow for your grass seedlings to thrive, it could allow for the perfect environment for fungus to destroy all your hard work.

You will begin to see brown patches in your grass as it begins to take hold, even if you have watered perfectly and winter is approaching. This my friend is fungus. Luckily we have a list of the best fungicides for your tall fescue.

Not all fungus is bad so it’s important to have healthy fungus intact in your grass root system for a rich and thriving soil environment. 

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