Guide · Feeding

"Winterizer" fertilizer: what it really is

It isn't a special formula. It's the last feed of the year — and it only makes sense for some lawns.

Cool-season lawns: yes, do the late-fall feed

Tall fescue, Kentucky bluegrass and perennial rye keep growing roots long after they stop growing leaves in late fall. A feed timed for then gets stored in the roots, not spent on top growth — and pays off as an earlier, greener spring without a spring growth surge.

• When: around your last mow of the year — the grass has slowed up top but is still green — and before the ground freezes.
• How much: about 1 lb of nitrogen per 1,000 sq ft (the bag tells you how much product that is).
• What: any good lawn fertilizer works. The "winterizer" bag is fine, but so is your regular feed. Extra potassium helps winter hardiness if your soil test shows it's low.

It's the last step of the fall program: a feed around Labor Day, another 4–6 weeks later, and this one at the end.

Warm-season lawns: skip the nitrogen

Bermuda, zoysia, St. Augustine, centipede and bahia are heading into dormancy. Nitrogen now pushes growth the grass can't use, feeds winter weeds, and can raise the risk of winter injury and spring disease.

• Stop nitrogen about 6 weeks before your average first frost.
• If you want to feed in early fall, use a high-potassium, low- or no-nitrogen product — potassium builds cold and disease tolerance.
• Put your fall effort into a pre-emergent for winter weeds (Poa annua) instead.

Local rules: some states and counties restrict fertilizer at certain times of year (parts of Florida ban it June–September) or limit phosphorus on established lawns. Check yours.