When to Apply Pre-Emergent in Florida
Soil across Florida rarely drops below the 50°F application floor, so spring pre-emergent is timed by the calendar rather than a soil crossing: get it down in late winter, ahead of the first warm spell. The fall poa annua barrier goes down around November 23.
Typical Spring Pre-Emergent Window in Florida
Soils in Florida rarely drop below the 50°F application floor, so there is no spring soil crossing to wait for: time the barrier by calendar, in late winter, ahead of the first warm spell, and water it in.
Spring pre-emergent and spring seeding are an either/or on the same turf: a standard pre-emergent blocks grass seed for the length of its reseeding restriction, which covers the spring seeding window. Mesotrione is the one cool-season exception. For a lawn being seeded this spring, see when to plant grass seed in Florida and the spring overseeding guide.
| Region | Typical spring window opens | Typical fall window opens | Stations |
|---|---|---|---|
| Northern Florida | — | October 30 | 2 |
| Central Florida | — | November 28 | 2 |
| Southern Florida | — | December 12 | 2 |
The 55°F Rule
Crabgrass seed germinates once 2-inch soil holds 55°F for several consecutive days. A pre-emergent works by forming a barrier the seedling cannot grow through, so it must be down and watered in before that crossing; applied after it, the product does nothing for seed that has already sprouted. The spring pre-emergent guide covers the research behind the threshold and the growing-degree-day cross-check.
Fall Pre-Emergent Timing for Poa Annua in Florida
Annual bluegrass (poa annua) germinates as soil cools in late summer and fall. The ideal application band opens as 2-inch soil falls back through 70°F, typically around November 23 in Florida, and ends as it passes 65°F, typically around November 29. Applications stay worthwhile until soil drops to about 55°F, after which most of the season's poa annua has already germinated.
Fall pre-emergent and fall seeding are an either/or on the same turf: the barrier that stops poa annua also stops grass seed. A lawn being overseeded this fall skips the fall pre-emergent; see when to plant grass seed in Florida and the fall pre-emergent timing guide.
Product Selection and Application Tips
Look for products containing prodiamine, dithiopyr, or pendimethalin. Dithiopyr has mild post-emergent properties and can suppress very young crabgrass even if applied slightly late. Weed-and-feed products that pair fertilizer with a pre-emergent follow the same soil-temperature window: the preventer half only works if it is down before the 55°F crossing. Water lightly within 24 hours of applying to move the product into the top layer of soil where weed seeds germinate, and keep to the label's annual maximum.
Common products
- Liquid, needs a pump sprayer: Prodiamine (Barricade)
- Granules, for a spreader: Scotts Halts (pendimethalin)
Check Your City
Timing varies within Florida: each city page tracks the live 2-inch reading from its nearest station against both windows. See when to apply pre-emergent in Miami, when to apply pre-emergent in Orlando or when to apply pre-emergent in Tampa, or find your city on the Florida soil temperature page.
Typical dates are computed from historical 2-inch soil temperature averages at 6 monitoring stations in Florida; your own window depends on your nearest station's readings.