Cheating the Season: Tips for Expanding Your Garden After the First Frost

By Deborah J. Benoit, Extension Master Gardener, University of Vermont

Everyone is probably running into the garden on an autumn evening when the temperature drops and a frost warning is issued. We place a sheet over our fruit-covered tomato plants to give the rapidly evaporating season a little more growing time. Aside from the ghostly visions of tomato plants covered in leaves, there are other ways to extend the harvest.

Knowing the average date of the first fall frost in your location can help you decide when to plant your garden or make preparations to extend the growing season. To find the average first frost date for your location, visit garden.org/apps/frost-dates.

Once you determine the average first frost date, look around your garden. Which plants are still productive? Plants growing in pots can be moved to a greenhouse or enclosed porch to protect them from the cold.

For ground plants, there are several alternatives to extend the growing season. Of course, there’s also the tried-and-tested covering of plants like tomatoes with old sheets or blankets when frost is forecast. Make sure you cover the plant completely to avoid damage to leaves and fruits. In the morning, remove the cover to gain access to the warmth and light of the sun.

If you have one on hand, a convenient alternative is to overturn a cardboard box over smaller plants and cover them completely, with the open end of the box resting on the ground. This process creates an easily removable protective structure around the plant in the morning.

Enclose tomato cages with clear plastic. Drive stakes into the ground just outside the plant’s perimeter and wrap plastic wrap around the stakes and over the top to enclose the plant without touching the foliage. During the day, provide an openable space where excess heat can be released.

If you’d rather not build a tomato cover, you can purchase pop-up plastic plant covers online or at garden supply stores.

To protect multiple low-growing plants, try floating row covers. Place a piece of garden fabric over the plants to protect them from the cold. Hold the edges with garden staples or weights. Remove the cover on warm days.

Garden fabric is made of spun polyester. It allows light and water to penetrate and is available in different weights. Choose a heavier weight to insulate against the cold. If temperatures continue to drop, a plastic sheet can be placed over the garden fabric to provide additional insulation.

For larger plants, consider using low tunnels. They function like floating row covers, but feature a series of inverted U-shaped supports that raise the fabric above the plants. At the end of the row, the fabric falls to the floor and closes the tunnel. To prevent overheating on warm days, the ends can be opened and closed again when temperatures drop.

If you are growing hardy lettuces (kale, chard, spinach) or root crops (carrots, beets) in a raised bed, you can add a cold frame to extend the harvest season further into the fall.

A cold frame is a box with a transparent lid that hinges so it can be opened when needed to release excess heat. At night the closed cover protects the plants. For best results, it should be in a south-facing location with direct sunlight.

Even cold-resistant varieties stop growing when temperatures drop. Eventually they will go dormant, but you can still harvest leaves and roots for a while.

These techniques can be used again in the spring to jump-start your gardening year.

Deborah J. Benoit is a UVM Extension Master Gardener from North Adams, Massachusetts, part of the Bennington County Chapter.

For more information about extending the growing season, visit: go.uvm.edu/season.