How long can frost protection covers remain on plants?
Written by
Benjamin Miller
Reviewed by
Prof. Samuel Fitzgerald, Ph.D.Daily removal of frost protection covers is necessary for the plants' sake. Remove covers as soon as the ambient temperature reaches above freezing (this is usually around 9 AM). If covers are left on the plants, they create perilous heat buildup and block critical sunlight. This ultimately stresses the plants and renders the purpose of protection moot.
Heat accumulation occurs quickly in covers. By mid-morning, temperatures can rise to 20°F higher than ambient air. This results in damage to plant tissues, leading to wilting. I have witnessed tomato seedlings kill themselves under forgotten plastic covers in just two hours due to sun exposure.
Morning Removal
- Check temperature at plant level before removing
- Remove when consistently above 35°F (2°C)
- Fold covers inward to contain debris
Daytime Storage
- Shake off moisture before storing
- Hang or spread flat to dry completely
- Keep in shaded, rodent-free location
Multi-Day Frost Events
- Reapply covers only after temperatures drop below 40°F
- Allow 4-hour sunlight exposure between applications
- Inspect plants daily for stress signs
Sunshine reduction inhibits growth when covers are left too long. All plants need 6-8 hours of light for photosynthesis each day. If the covers stay on, the plants will develop yellowing leaves, and the stems will become weak. If there is a stretch of cold weather, switch the covers around to give the plants some sunlight.
Adjust cover time based on weather. Extend cover for 1-2 hours in cold, cloudy weather when temperatures are below 50°F. For sunny days, uncover right at sunrise. I set phone alarms based on the local sunrise time in the frost season.
Rehabilitation from excessive stress should commence immediately. Provide deep watering without wetting foliage. If the foliage is sun scorched, provide it with partial shade to allow it to recover for 48 hours. Prune only the obviously dead material! Most plants respond and recover beautifully after cover mishaps, with a little aftercare.
Read the full article: How to Protect Plants from Frost Effectively
