Volume 13, Issue 38 ~ September 22 - September 28, 2005
Dr. Gouin's Bay Gardener

Beat Back Weeds by Cutting Your Lawn Tall
Easier on lawn, mower and you

If you want that new lawn we’ve been working on (See issues 36 and 37) to be weed-free and drought-tolerant, set the cutting height of your lawnmower to at least three inches; three and a half is even better. Mowing your lawn high encourages deeper rooting, provides competition to weeds, produces a denser turf and saves energy. What’s more, you won’t have to sharpen your mower blades more than once yearly. I generally allow my grass to grow to about five inches tall before I mow it.

You also want to mow your lawn often enough — at least weekly in high season — that you will only be mowing leaf blades, not grass stems.

By mowing your grass tall, you are allowing each blade of grass to produce more food for the root. Taller blades of grass also shade the soil, thus reducing the amount of water loss by evaporation. In addition to keeping the soil cooler, grass clippings filter down between the blades and decompose in place. Letting clippings lie works for you in many more ways: by more rapidly recycling nutrients back into the soil; by avoiding the accumulation of thatch; by reducing your fertilizer bill by one-third to one-half.

Mowing your grass tall also saves energy. It takes much less power to cut the grass tall than to cut it short. Blades of grass are much less dense than stems. Short-cut grass means more stems mowed, not to mention more objects hit, such as stones, branches and toys. In other words, mowing your lawn tall is also safer.

That’s why my motto is Cut it tall and let it fall.

Too Much of a Good Thing Becomes Thatch

We live in a Zone 5 area in south-central British Columbia. I found you in Bay Weekly while researching the use of weed-and-feed fertilizer. Having read your article, I have reconsidered using this sort of product.

My question to you regards the yard waste we generate throughout the year and specifically in the fall. 

When I prune my hedges and perennials and when we weed the plant beds, we throw the waste onto the lawn and I mulch it with my lawn mower. We do the same in the fall when we pull up the annuals and cut back the perennials. I do not rake the leaves from our four maples either; they all get chopped up by the mower. This has not harmed my lawn, but I am wondering if it is wise to continue or whether some adjunct fertilizer is needed to go along with all this organic material.

—Richard Chmilar, Sicamous, British Columbia

A By increasing the amount of organic matter over and above what grass clipping would add, you increase the amount of thatch that accumulates in your lawn. You might have to de-thatch or top-dress your lawn with compost to rot the thatch in place.

Ask Dr. Gouin your questions at frgouin@erols.com. All questions will appear in Bay Weekly. Please include your name and address.

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