Moving grass
May 19, 2010 10:59 AM   Subscribe

Does mowing grass promote outward growth?

In our household, it has been theorized that mowing grass causes it to grow outward (spreading) instead of up. That is, somehow, since it has been cut, it decides to grow outward with tillers. Is this true or is it a myth?
posted by allelopath to Home & Garden (5 answers total) 4 users marked this as a favorite
 
Nope, it's true. Grass has two growth modalities:

1. I'm being repeatedly cropped by grazing animals (or a lawnmower)! Therefore, I will reproduce myself by spreading laterally with runners and vegetative growth.

2. There are no animals around to eat me, so I will spread my seed! I will grow very very tall, and sprout flowers, and release pollen which will make ErikaB sneeze for three weeks straight.

#1 is better for our purposes, because it helps fill in the grass and make it grow more thickly. A thick turf not only looks better, but it crowds out weeds so you can get by without having to use weed killer. And since mowing favors grass over weeds (which are harmed by having their heads chopped off, unlike grass) the simple act of mowing more often is a mechanical method of weed prevention.

This is why experts advise that you cut the grass more often but with a higher blade, rather than mowing it way short but less often.

Think of it like a very unusual sort of pruning.
posted by ErikaB at 11:28 AM on May 19, 2010 [4 favorites]


I know that grasses evolved with grazing animals. They both came on the scene and were, and are, codependent (in a good sense). So mowing takes the place of grazing and is not unfamiliar to the plants.

As far as mowing encouraging the plants to put out rhizomes, not sure.

This might help.
posted by Danf at 11:29 AM on May 19, 2010 [1 favorite]


Anecdoally, "pinching" other kinds of plants (taking the new growth off the top) causes them to grow more bushy, or outward, than upward and spindly.
posted by Brittanie at 12:20 PM on May 19, 2010


Response by poster: It is a good point that grasses evolved being grazed, and that mowing is similar to grazing.

>>1. I'm being repeatedly cropped ... Therefore, I will reproduce myself by spreading laterally with runners and vegetative growth.
This is giving more intelligence to grass than I would grant. "Repeatedly"... 3 times? 5 times? At what point does it decide to spread laterally?

>>mowing favors grass over weeds (which are harmed by having their heads chopped off, unlike grass)
Didn't weeds evolve being grazed, too? How is it that grass has the advantage?
posted by allelopath at 12:20 PM on May 19, 2010


Weeds didn't evolve to be grazed, with a few exceptions. Clover comes to mind - it's a valuable animal forage, and it too develops a low spreading habit when its head keeps getting cut off.

Most other weeds aren't grassland plants at all. Many of them spend a lot of effort trying to NOT be eaten by animals. Spines, toxins, bad tastes, etc.

As to "repeatedly," I have learned that if you mow a field in the very back of the property, and then ignore it for a couple months, it goes to seed. So obviously the answer is "more than once a season"!

You'd have to do some experiments to find out the specific period. For my lawn, mowing weekly during its main growth season is enough to encourage vegetative/spreading growth and keep the grass from going to seed.
posted by ErikaB at 3:46 PM on May 19, 2010


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