How long should plants stay covered?
Written by
Paul Reynolds
Reviewed by
Prof. Martin Thorne, Ph.D.Proper timing of frost cover removal inhibits overprotection injury. However, covers left on too long can trap humidity and block sunlight. I once lost an entire row of tomato seedlings for leaving them wrapped for 72 hours. Their leaves yellowed from lack of light, even though temperatures were above freezing.
Removal Guidelines
- Peek under covers at sunrise if above 32°F
- Remove layers gradually over 30 minutes
- Secure covers for reuse if frost returns at night
- Sterilize reusable fabrics weekly with vinegar spray
Risk Management
- Rotate covers side-to-side for partial light access
- Insert bamboo stakes to create 4-inch air gaps
- Monitor soil moisture under wraps with probe tools
- Prune touching foliage to prevent fungal transfer
Microclimates can certainly dictate removal schedules. For example, my tomatoes in the greenhouse must be uncovered midday during the winter, even if it is only 35°F outside. In the desert, I often can remove them earlier than my coastal friends. Check on local dewpoints. High humidity tends to necessitate more urgency in their schedule. I also have used wireless thermometers with alerts to help me time when I can remove the cover.
Consideration of regional differences is imperative. Gardeners in Minnesota may leave their covers on for 5 days while enduring polar vortices, whereas growers in Florida take off the covering by 9 AM after a light frost. So, when plans are made, you will naturally adapt them according to your last frost date. My zone 7 garden favors an 18-hour maximum amount of time covered when overwintering most perennials.
Read the full article: 12 Ways to Protect Plants from Frost: Expert Tips
