What is the Best Height to Cut Grass in the Fall?

Did you know that the best grass height depends on the season? Shorter grass in the spring changes to long grass in the summer to best protect it from the heat. But what about autumn? What can you do that actually ensures that your lawn has the best head start in spring?

The best height to cut grass in the fall is between 2.5 and 3 inches for cool-season grasses, and 1.5 to 2 inches for warm-season. Longer grass blades mean your grass has more nutrients stored to survive the winter, and when spring arrives, the grass has a lot more leaf for photosynthesis. Cutting shorter than this weakens your grass.

What is the Importance of Grass Height During Fall?

Fall is when your lawn is preparing to survive the winter by gathering and storing food. Grass stores carbohydrates in its roots and in its crown, the part that grows above the soil that the grass blade grows out of. Cutting the grass blades too short interferes with your grasses’ ability to store energy. Longer grass blades also help protect the soil and the grasses’ roots from cold temperatures.

Too short means that in early spring, your grass has to put a lot of energy into growing taller, while not being able to photosynthesize as well as when it had longer leaves.

However, you also don’t want to just stop mowing and let the grass grow long. Long grass will get matted, causing you trouble in the spring, and provides a haven for mice and voles.

Once the grass grows again in the spring, you can mow a little shorter.

When is the Last Time to Mow Grass Before Winter?

Your last cut before winter should be while the grass is still growing and before the first frost. Cool-season grasses stop growing once daytime temperatures drop below 50F or 10C. Depending on where you live, that could be as early as September, or as last as November.

How to Prep Lawn in the Fall for Winter?

Apply Fertilizer

Fall is the best time to apply a compost fertilizer or compost tea, as the compost will continue to break down before the ground freezes and start again when the soil thaws, providing your lawn a head-start come spring.

If you overseeded this year, apply a potassium-rich fertilizer or soil amendment like kelp and wood ashes.

If you’re in a warm-season zone and overseeded with cool-season grass for winter colour, then apply a nitrogen-rich fertilizer like fish or alfalfa meal to amp up the green.

Water Your Lawn (If It’s Been Dry)

If the weather has been dry, give your lawn a deep watering. Once the soil freezes, the roots won’t be able to get anything else until the spring thaw.

Keep Those Weeds From Going To Seed!

Weed seeds that reach the soil in the fall can germinate before winter or in the early spring, and before you know it, they’ve overtaken your lawn. A bit of precaution now will save you a ton of stress come spring.

It’s best to hand weed, but if you’re drowning and those weeds just keep developing their seeds (don’t worry, we’ve all been there), then mow with a bagger attachment. The mower will cut off all the seed heads, and the bag will keep them from landing on your land.

Ideally, you’d then decompose the weeds in a really hot compost pile. High heat will destroy the seeds. But if that’s not possible, then bag them for yard waste pickup.

Remove Or Mulch Leaves In Place

Dried leaves may become nutritious food for the soil, but if they cover more than 10 – 20% of your lawn, they could end up inhibiting early spring growth, promoting snow mold diseases, and harbouring mice and voles, who can cause extensive damage.

But that doesn’t mean you can’t use them! Either rake them up for the compost pile, or run over the leaves several times with the lawn mower to turn them into mulch. Over the winter and into the early spring, the leaf mulch will break down into usable nutrients. Like when applying compost, leaf mulch shouldn’t be so thick that it swallows up the grass blades.

Some tree leaves, like maple, inhibit weed seed germination, while others, like the honey locust, are high in nitrogen. Take advantage!

Cut Grass To Its Final Height For Winter

Before the first frost of the year, cut your lawn to its final height, either 2.5 – 3 inches for cool-season, or 1.5 – 2 inches for warm-season. Don’t take off more than a ⅓ at a time. If you get behind with the mowing, do several short cuts over a week.

Stake Out Edges Of The Lawn

Your lawn may survive snowplows, footfalls, and cars parked on it during the winter, but when spring comes, your lawn will look ragged. Before the ground freezes, stake out where the lawn is so that it’s obvious where the sidewalks and drives end, and where the lawn begins.

If you have someone plowing your driveway, find a place that’s not your lawn to dump the snow. Come spring, large mounds of snow will take a long time to melt and can winter-kill the grass below. If you don’t have another choice, then spread out the snow pile as it melts.

Should I Add Grass Seed in the Fall?

If you’re overseeding with cool-season grasses (including if you’re in a warm-season zone), then fall is the best time to add grass seed. The warm, sunny days and cooler, dewy nights in autumn provide the best environment for grass to grow. Aim to overseed in the two weeks before or after Labour Day (the sooner that first frost comes, the earlier you should overseed). This gives the new grass the best chance to germinate and establish itself before winter comes, then the whole spring to continue growing so it can take the heat of summer.

If you’re in a warm-season or transition zone and planting warm-season grasses, then the best time is in the early spring.

Final Thoughts

Preparing the lawn for winter can pay big dividends come the next growing season, and it starts with the right height for your lawn. At 2.5 inches for cool-season, and 1.5 inches for warm-season, your grass will survive the winter and thrive come spring.

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