Grass in forests, parks, public spaces, etc.

[luckystrike]

Why do grassed areas in forests, parks and other public spaces not quickly become over-run with weeds and thistles?

[woofgang]

well in the new forest, it is cropped by cows, donkeys and horses. In manicured parks it is mowed regularly

[woofgang]

hit enter too soon. If you look closely on the grass, you will find loads of small non grass plants in most un manicured public open space

[TonyV]

normally lack of light to germinate seed

[hammerman]

I work for Brighton parks and the only reason i can think of is that the open spaces are regularly mown fairly low and the larger weeds tend to just give up.

Must admit that i'd never given it a thought until now although im pretty sure there will be plenty of smaller, lawn weeds in the grass.