I am told that short lawn grass grows faster than long, is this true, why?

Question

It is my reasoning that long bladed grass grows faster because there is more area exposed to the sun causing photosynthisis to be greater, thus more growth.

Answer 1

I can imagine the myth of short grass growing faster came about because the apparent change in length was greater in short grass than in long. If the grass is one inch and grows 1/2 inch it has increased 50% but if the grass is three inches and grows 1/2 inch it has increased 15%. Not a noticeable change visually but in reality just as much growth.
Grass grows the same given the same conditions whether it is short or tall. Tall grass does shade its own roots but that has more effect on the competition than itself. Weed seeds require daylight for germination so in tall thick grass the weeds are blocked from germination. Given equal levels of soil moisture and nutrients short grass will grow at the same rate as tall. Of course the reality is that short grass will suffer more in high temperatures, dying sooner than tall grass.
Tall blades of grass do photosynthesize more with more area so are able to withstand frequent mowing much better than plants that grow from an apical meristem (the tender new growth at the shoot tips of a plant) because grass has new growth close to the ground, pushing the blades older portions up to the sun. The top you mow off is the oldest portion of the grass blade.
If you mow grass to short you can remove their meristem. If you look at a blade of grass it grows from the ground in a sheathed stalk. Above this it flares open from a collar. All growth is from the collar. The taller it gets the more blades a stem can have so it is thicker as well as taller.
Mowing grass frequently injures plants with apical meristem allowing grass to rapidly out compete weeds, especially with enough nitrogen to support this continuous growth.

Answer 2

Simply put, No. In fact, as a few people pointed out here- there are many myths regarding lawn care.
Your best bet would be to cut the grass "high"- ...3 inches is considered best practice by any and all cooperative turf organisations. This is the optimum height to encourage root growth, conserve soil water retention and crowd out weeds. Its best doing this starting in spring for a full season - but starting now would be great as fall is a regeneration period for turf.
If nothing else...
There is absolutely no truth to the photosynthesis theory you mentioned... whomever is giving you this advice is terribly misinformed.

Answer 3

>> I am told that short lawn grass grows faster
than long, is this true, why? <<

Not true.

But not for the reason you posted... sorry.

Longer grass provides more shade to the tender root / "new growth" part of the plant, thus it's healthier and stronger and the wind won't evaporate as much of the ground moisture and... oh yeah, it requires significantly LESS water.

Shorter grass... ugh... get two days of sunshine and you'll have the sprinklers on 24/7 to keep it from yellowing.

Hope this helps,
      TX Griff

Answer 4

I believe you are right, the experts say, mow high, and often. Don't forget to water at least twice a week, preferably more.

Answer 5

Do you believe in the Tooth Fairy too?