I am in the process of converting a tiny "lawn" area a la Paul's
lawn article. My wife REALLY wants a little bit of lawn, which is fine, she puts up with all sorts of my shenanigans out there.
The only downside with crabgrass is that it is quite allelopathic. I have areas that are bare as can be all winter, and I planted several varieties of
perennial grasses last fall. They all came up sickly and never really thrived. In one area I took great pains to remove the
root balls of the crabgrass, and they perennial grass is doing well. Probably with Paul's lawncare plan the perennial grasses would gradually work into the bare areas, but it may take a long, long time. I think the best thing for a really crabgrass-infested area might be to amend/till, plant clover and perennial grass in the fall (depending on your climate maybe early spring) and hit the reset button. The soil where the crabgrass is dominant is dirt, it is exposed for probably 7-8 months a year at least. Alternatively some
straw mulch in the summer to inhibit the warming of the soil may be super, crabgrass needs pretty warm soil to germinate and grow avidly, since it is a C4 grass.
This is not an area I am spending much time but I get more questions from my friends about lawns than any other topic, by far! I consider lawns a gateway drug to
permaculture...