Preen Garden Weed Preventer (Trifluralin) Review (2026)
By The DIYPicks Team · Updated July 2026
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- Flower beds
- Mulched beds
- Pre emergent control
- Low effort maintenance
A pre-emergent for keeping weed-free beds weed-free: trifluralin granules block weed seeds from germinating for up to 12 weeks, so an existing, cleaned bed stays clean with little hand-weeding. It's easy to shake around shrubs and ornamentals. Because it blocks all seeds, never use it where you're sowing seeds or seeding a lawn, weed the bed first, water it in, and follow the label around edibles.
Pros
- Stops weed seeds from sprouting for up to 12 weeks, so beds stay clean with far less hand-weeding
- Granular shaker is easy to apply around established ornamentals and shrubs
- One spring application dramatically cuts the season's weeding workload in mulched beds
Cons
- Purely preventive: it will not touch weeds that have already emerged, so weed first
- Also blocks desirable seeds, so never use it in beds where you're direct-sowing seeds or before seeding a lawn, and follow the label for edible gardens
- Must be watered in and reapplied every 9-12 weeks to keep the barrier intact
Specifications
| Type | Pre-emergent (stops weed seeds from germinating) |
|---|---|
| Active ingredient | Trifluralin 1.47% |
| Duration | Up to 12 weeks per application |
| Coverage | About 1 lb per 1,000 sq ft (31.3 lb covers ~5,000 sq ft) |
| Limitation | Does NOT kill weeds that are already growing |