skip to main content

Ask The Yard Doctor

Is this lawn-care addage just a myth?

15 years ago

"Let your grass grow long and it will choke out weeds."

From my experience, this seems like an old wives tale.

I see lawns and fields (my own and others) that have really tall grass and so they also have really tall weeds.

I understand the premise behind the addage, but in actuality, my lawn is at least 25% clover and probably a good 15% a large variety of weeds. They don't bother me; when I mow the lawn the whole thing looks nice. If I were to let the grass grow long, the weeds would still be there and just grow along with the grass.

Thanks for any opinions!

:)

-Katy

Sort by:Oldest

Comments (3)

andee_gw
15 years ago
Glad you have the courage to point this out -- it's my experience also. That "clover" just keeps climbing. I think it is not so much how high the grass it (although mowing it high keeps it healthier) it is how thick it is. Good thick grass will choke out many weeds.
gk5040
15 years ago
In the hot summer months, what you dont want to do is cut the healthy lawn too low that you allow the sun to dry and burn it out. Then the weeds will take over.
Related Discussions
The myth, of the high P myth?
Q
Comments (39)
Let's say your regular fertilizer program is 3 parts of 9-3-6 in a gallon of water. To reduce the N supplied and slow vegetative growth, you start supplying 2 parts of 9-3-6 per gallon. By reducing the CONCENTRATION of the solution to 2 parts per gallon, you cut the amount of all the nutrients by 1/3, not just the N. This reduced concentration still has enough P to keep your plants happy, but not quite enough K, so you need to add a little more K by adding potash to the soil, or by supplementing with Pro-TeKt or another K-containing product to be sure all the bases are covered. ************************** This is more about theory than anything - for those who want to manipulate the growth habits of certain plants by reducing the N supply and still be sure they are not inviting a K deficiency along with the planned deficiency of N. It's nothing to get frantic about. Al
...See More
Is this lawn care addage just a myth?
Q
Comments (2)
There's a difference between mowing grass tall and letting it go completely. One of the side effects of mowing is to encourage rhizomes and tillers, so the grass tends to fill in better. If there are already weeds in the lawn, simply growing the grass tall won't get rid of them. You need to get rid of existing weeds, because the tall mowing only helps keep other weeds from sprouting. There are really several things involved, sometimes called cultural practices. One is to mow tall. Another is to mow no more than 1/3 of the height of the grass. Another is to water deeply but infrequently. The 1/3 rule doesn't directly discourage weeds, but it helps keep the grass healthy. watering infrequently makes it difficult for the weeds to germinate (they need to stay moist for a while to germinate). If they somehow stay moist long enough to germinate (regular rainfall, for example), the tall grass will block sunlight so the weeds that do germinate don't survive.
...See More
Does more fertilizer mean lawn requires more water?
Q
Comments (24)
Can I add something? For the needs of the grass, who cares water 1/3" 3 times a week or all at once one time a week. If you have the ability to water the lawn, why worry about attempting deep root growth for drought resistance...there will be no drought if you can water regularly, right? BUT If you keep that top 2" of soil always moist, the grass will be happy, but so will the weeds that do not have deep roots. Since my KBG has matured, I barely water. I wait for the grass to stress for a day or two, then hit it all night with about an inch of water over ten hours. The weeds have disappeared, and I can go 7-10 days or so without rain or water. Most weeds are shallow rooted and can't withstand dry soil conditions for several days. We all have different soil types, grass types, and enviromental conditions to contend with so no two people can expect to have the same schedule work for them. There will be adjustments in watering frequency and amounts needed. I still think it helps to keep the top layer dry to control weeds and prevent fungus and disease as well. Oh well, whatever works best for you right?
...See More
Ponderosa pine and similar tree care
Q
Comments (23)
Good pics. In the first one, the mulch mat looks like it is depressed towards the trunk as in, the tree was planted too deeply. But that tree still appears healthy so I'd not mess with trying to replant it. All the trees, in fact, have a generally good appearance. Foliage color is good, and growth rate, while not anything we'd call rapid, still falls within normal range. By far the number one thing I would do would be to expand the area free of turf around each tree. Turf is really a tough competitor for young trees. You could kill off another foot-wide strip around each one with glyphosate-style herbicide (Roundup) and then mulch. If you're not comfortable with the herbicide, you could just mulch over the top of the (Mowed) turf and rely on that to at least kill off some of the grass. Smothering with several layers of cardboard or newspaper really does work too, and then the mulch can go right over this rotting stuff. Woodchips or bark make perfectly acceptable material for mulching, and no other practice comes close in terms of cost/benefit ratio. Other than that, I really see no other problems. Very moderate nitrogen fertilization could be done, but if it were me, I'd wait until the expansion of the mulch rings was already in place for a while. In other words, fertilize trees that are already happy with their situation. As far as the rubber mulch mats, it is possible they could just be left in place and mulched over and around. Don't really see why not, though I've never used them. +oM
...See More
yarddoctor
15 years ago
Dear Andee

Thanks for the inquiry. The adage of let your grass grow tall to choke out weeds is correct to a point, but it is slightly taken out of context. First if there are already weeds, it will not work, you are right. The taller grass will shade out new weeds from getting the light necessary to germinate, but not the ones that are already there. Second, you need fertilizer to allow grass to spread and out-compete weeds. If this is not present, the yard is out of balance. Lawn care is like a three legged stool, with the legs being proper mowing, fertilizing and watering. If these legs get short, long or weak, the weeds will have a chance to compete (and some will anyway, regardless, as perfection is hard to attain, and even harder to maintain. Consider the following as some starting guidelines.

To begin with, you must mow frequently and follow the one-third rule. This means never cut more than one-third of the leaf blade off in any single mowing. This promotes turf density and the density is the key to preventing the light requirement for the weed to germinate. Second, follow a balanced nitrogen fertility plan. Apply judicious amounts of nitrogen when the grass is actively growing. For cool season grasses, this centers on spring and fall and for warm season grasses, late spring and summer. Do not over fertilize as this will cause rapid growth and then you will end up scalping the grass if you cannot keep up with the mowing and then weeds can encroach.
The final issue is watering. This one is not straight forward as climate, soil type, grass, and time of year will dictate the water needs of the plant. One rule to begin with is to assume that your turf will need 1.0 inch of water per week during the growing season. This can be applied in a variety of ways and rainfall needs to be counted in the total. For best results, try to water early in the morning. The wind is at it least and you can be the most efficient with the least contribution to disease pressure.

Again, thanks for the question and let me know if you have more.

Respectfully

Trey Rogers, The Briggs & Stratton Yard Doctor, YardDoctor.com

Related Stories

GARDENING GUIDES Garden Myths to Debunk as You Dig This Fall and Rest Over Winter

By Benjamin Vogt / Monarch Gardens

Termites hate wood mulch, don’t amend soil for trees, avoid gravel in planters — and more nuggets of garden wisdom

GREEN BUILDING 6 Green-Roof Myths, Busted

By Mariana Pickering (Emu Building Science)

Leaky, costly, a pain to maintain ... nope, nope and nope. Get the truth about living roofs and see examples from simple to elaborate

GARDENING GUIDES Common Myths That May Be Hurting Your Garden

By J. Peterson Garden Design

Discover the truth about fertilizer, soil, staking and more to keep your plants healthy and happy

GARDENING GUIDES We Bust 4 More Native Plant Myths

By Benjamin Vogt / Monarch Gardens

Have you been taken in by these fallacies about gardening with native plants?

LANDSCAPE DESIGN Get Along With Less Lawn — Ideas to Save Water and Effort

By Jocelyn H. Chilvers

Ditch the mower and lower your water bill while creating a feast for the eyes with diverse plantings and gathering places

MOST POPULAR Meet a Lawn Alternative That Works Wonders

By Benjamin Vogt / Monarch Gardens

Carex can replace turfgrass in any spot, is low maintenance and adjusts easily. Add its good looks and you’ve got a ground cover winner

BEFORE AND AFTERS See 6 Yards Transformed by Losing Their Lawns

By Annie Thornton

Wondering whether a turf lawn is the best use of your outdoor space? These homeowners did, and they found creative alternatives

GREAT HOME PROJECTS How to Replace Your Lawn With a Garden

By June Scott Design

New project for a new year: Lose the turfgrass for energy savings, wildlife friendliness and lower maintenance

FRONT YARD IDEAS Before and After: Front Lawn to Prairie Garden

By Benjamin Vogt / Monarch Gardens

How they did it: Homeowners create a plan, stick to it and keep the neighbors (and wildlife) in mind

GARDENING GUIDES How to Prep Your Ground for a Healthy New Lawn

By J. Peterson Garden Design

Seed or sod that falls on weedy, lumpy soil is a wasted effort. Follow these steps to ensure that your new lawn will thrive

Sponsored

More Discussions

Are my newly viburnums dead or dying?

3

Can I recover the structure of this tree?

0

Cement or pavers- which is better?

9