how can weed and crabgrass killer target said specific plants without damaging common types of grass?
In: Chemistry
One method is used on broadleaf weeds and another method on crabgrass.
Lawn grass has a narrow leaf. Lawn weeds such as dandelions are broad leaf. (Crabgrass is not a broadleaf.)
Broadleaf weeds absorb water through their leaves. Grass doesn’t. So, the herbicide used to combat broadleaf weeds is effective only on plants which absorb water though crabgrass. Broadleaf herbicides are actually growth hormones, which cause the plant to grow very quickly.
Crabgrass is a significant problem. Herbicides that kill crabgrass also kills lawns.
So, the usual plan to deal with crabgrass is to dig out the plants. Then, a pre-emergent herbicide is applied. The pre-emergent coats seeds and stops them from germinating. Most lawns have a perennial grass, and thus don’t rely on seeds for spreading.
The key to effective crabgrass control is to apply the pre-emergent at the correct time of the year.
I don’t actually think they’re that specific. But they tend to work better on fast growing plants.
Plants have certain processes that keep them alive and help them grow, and different types of plants can have different processes. Weed killers and herbicides can be made to target processes that happen in weeds and not in common grass.
Edit: not all weed killers are like this. They can also be non specific and kind of just kill everything. If you’re buying just be careful on what brand you buy and do some research before you destroy your lawn
In the large commercial crop business, companies like Monsanto genetically modify its plants to be resistant to their own weed killers.
Organic produce don’t do this (or on a much less impact full way).
Some of it is clever marketing. Clover used to be a common part of lawns. Clover is killed by most broadleaf herbicide. Herbicide companies convinced people that it shouldn’t be part of ‘good’ lawns. 70 years later broadleaf herbicides are harmless to good lawns.
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