Perennial Ryegrass

Ryegrass carrying a live fungus inside its leaves that makes them toxic to leaf-feeding insects — pest resistance with no insecticide.

Best For: A lawn with a history of chinch bugs, sod webworms, billbugs, or cutworms, or any yard where you would rather not spray for them. It also runs on slightly less nitrogen than plain ryegrass.

Tradeoff: The protection is a living organism, so it expires — seed stored warm past about nine months buys you nothing — and even fresh, it does nothing against root-feeding grubs.

Ryegrass bred against the one disease that can take a healthy stand to bare ground in a matter of days.

Best For: Any ryegrass going into ground where July is hot and muggy — roughly south of Interstate 80, through the Mid-Atlantic and the transition zone — and any winter overseeding of a dormant southern lawn.

Tradeoff: Resistance is not immunity, and it does nothing about ryegrass's other summer problem — heat with no dormancy to fall back on.

The plain improved ryegrass that fills most bags — the fastest cover of any cool-season grass, at the lowest price.

Best For: A sunny northern lawn that needs grass on the ground fast and takes real foot traffic — a new yard, a worn play area, or a bluegrass lawn that needs a quick-starting partner. Best where summers stay mild and you can water through them.

Tradeoff: Nothing is bred into it against gray leaf spot or leaf-feeding insects, so in a humid summer your mowing and watering habits are the only defense the lawn has.