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Frost Threatens Gardens

Jack Frost is threatening our gardens. Learn which plants need protection and how to protect them.

Frost damage on tomatoes
Frosted tomatoes may burst open.

Jack Frost is threatening our gardens. It's time to protect our tender plants. 

Frost kills plants by exploding their cells. When cells freeze, they expand and the cell walls burst open. It’s like putting a can of soda in the freezer; the liquid expands and the aluminum can bursts! Frost-damaged plants look water-soaked and mushy.

Garden plants differ in their abilities to tolerate frost. The most sensitive vegetables include tomato, pepper, cucumber and squash. These plants require protection. Cabbage, kale and root crops (carrots and radish) tolerate light frosts.

The most sensitive flowers include geranium, impatiens, begonia, zinnia, portulaca and coleus. Hardier flowers include aster, cosmos, morning glory, marigold and petunia.

Frosted tomatoes
Tomatoes damaged by frost will look water-soaked and mushy.
How do you protect your plants? That’s easy. Pretend YOU are outside in the garden. What would you wrap around yourself to stay warm?

I would want a blanket and so would your plants. Cloth or burlap blankets can provide a few degrees of protection. Newspapers and plastic sheets provide less protection. 

Consider using layers of protection. Just like we use layers of clothes to keep warm, garden plants benefit from layers of protection. Two blankets are better than one.

This protection may give you an extra week of gardening. But when a hard frost (28°F or below) is expected, nothing will save your sensitive plants. Run outside and harvest whatever you can!

Written by , Extension Horticulturist, North Dakota State University. Photos were made available under Creative Commons licenses specified by the photographers: Anonymous and Emily.

Filed under: tomato, Tom Kalb, Frost, Gardening
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