Protect Your Plants and Trees Today: Six Top Tips Against Sudden Frosts
by John Campanini, Technical Director, RITree
The National Weather Service recently issued a freeze advisory for Rhode Island, indicating that temperatures drop as low as 29°F. Sudden, unseasonal frosts like this endanger plants and trees because they hit them before they have had time to prepare for cold weather. Cold acclimation or hardening is the key to plants and trees surviving the winter. The process is a fundamental, multi-step survival mechanism triggered by environmental signals and critical to a plant’s survival.
The primary danger for plants from a sudden frost is cellular destruction. When temperatures drop rapidly below freezing (32°F or 0∘°C), the water inside and surrounding plant cells freezes, causing them to expand and creating cell membrane rupture and dehydration. Trees, on the other hand, experience structural and systemic damage from rapid temperature decreases. That can cause frost cracking, bark splitting, root damage, and sap flow disruption, which create openings for pests and diseases.

Danger for Urban Trees
Sudden frosts tend to be more damaging to urban trees than those in natural or rural environments. A sudden frost can devastate new or tender growth in urban areas. Below, we break down two reasons why urban trees are more at risk from a sudden drop in temperatures than forest trees:
• Urban Heat Island (UHI) Effect and De-Acclimation
Cities are significantly warmer than surrounding rural areas due to pavement, buildings, and a lack of vegetation absorbing and radiating heat. This increase in temperatures is known as the urban heat island effect. This effect causes critical tree problems, like sunscalding and bark splitting, making city trees more susceptible to dehydration and worsening the damage caused by ice formation during a freeze. The effect is magnified for urban trees because they’re less hardy and prepared due to the artificial warmth and constant environmental stress.
• Compounding Urban Stresses
City trees already live under a perpetual state of stress, which severely limits their ability to recover from freeze damage. Urban trees often deal with compacted soil, a lack of nutrients, limited root space, and poor drainage, which weaken their overall health and resilience. Meanwhile, pavement and concrete limit water absorption, deicing salts used on sidewalks and roads damage tree roots and foliage, and cracked bark or dead branches open entry points for opportunistic pests and diseases.
Tips on Protecting Plants and Trees
The main goals of this process are to conserve energy and prevent lethal ice formation inside the plant’s cells. Here are seven tips on how to protect plants and trees:
- Cover plants with fabric: Drape old bed sheets, blankets, burlap, or commercial frost cloth loosely over plants and small trees. Use stakes or a frame to prevent the cover from crushing the foliage. Ensure the cover extends to the ground to trap the earth’s stored heat.
- Bring potted plants indoors: Move all container plants, especially tender annuals and tropicals, into a sheltered location like a garage, shed, covered porch, or indoors.

- Wrap young tree trunks: Young, thin-barked trees can be susceptible to frost damage. Wrap the trunks with a commercial tree wrap, burlap, or even cardboard to provide insulation.
- Water deeply before the freeze: Moist soil holds and re-radiates heat better than dry soil. Watering your plants thoroughly during the day before a frost is expected will help keep the root zone warmer overnight.
- Apply a thick layer of mulch: For in-ground plants and trees, apply a thick layer (about 3-6 inches) of straw, shredded leaves, or wood chips around the base. The mulch acts as an insulating blanket, helping to keep the soil and roots warm.
- Add a heat source (carefully): For very valuable or vulnerable plants, you can place a low-wattage heat source, like a strand of non-LED incandescent Christmas lights, under the cover to generate extra warmth. Always ensure the heat source is not touching the cover or foliage and does not pose a fire hazard.
A sudden, unseasonal frost endangers plants and trees because it hits before they have had time to “harden off” for cold weather. The primary danger to plants and trees when this happens is cellular destruction due to the freezing and expansion of water.
Urban trees are more susceptible to a sudden frost than forest trees thanks to the UHI effect and a combination of city stresses, like deicing salts, limited root space, and compacted soil. Implementing some or all of the six tips boosts your plants and trees’ chances of surviving a sudden frost.
For more information on protecting your plants and trees from sudden frosts, contact the experts at RI Tree.









