Gainan's Flowers & Garden Center

Gainan's Flowers & Garden Center

Posted by gainans on September 20, 2016 | Last Updated: October 6, 2020 Gardening

Planning for Fall Frost

This time of year I am literally counting the days until the first frost hits, hoping it will be later so I have time to get my yard ready for fall.  According to the Yellowstone County Extension Office, our average first frost date is September 22, but keep an eye on the weather forecast – a frost that will kill tender plants occurs at 26-30 degrees.

If you have vegetables that are still ripening or annuals that you are still enjoying, be prepared to cover them at night. Be sure to remove the covers by mid-morning, or else your plants may get too hot as the temperature rises during the day.

If Jack Frost sneaks up on you and leaves frost on your garden, spray with water before the sun hits the plants. If the frost was light, this may save your plants by thawing them slowly. If your vegetables froze, don’t rush to pick them – let the soil and plants warm before harvesting them. If we have a hard freeze, allow the ground to thaw before harvesting root crops.


Frost isn’t necessarily a bad thing. Several fruits, such as apples, chokecherries, plums, and gooseberries will continue to ripen and become sweeter after a frost; and potatoes and onions will store better after a frost kills the tops. Pumpkins and winter squash should be harvested after a light frost, but before a heavy freeze.

Keep watering, mowing and raking your lawn until winter arrives. Long, matted grass and leaves left over the winter may cause problems next spring. Stop watering your established trees and shrubs when they start to go dormant (leaves turn color and drop). Watering, fertilizing with high nitrogen fertilizers and pruning live wood can encourage a new flush of growth, which will make your trees and shrubs vulnerable during winter. However, if we have a warm and dry fall, we may need to apply more water. Continue to water newly planted trees and shrubs as usual. To protect tender, dark barked trees from sun scorch, wrap the trunks with tree wrap. If you had problems with insects or disease on deciduous trees or shrubs, fall is also a good time to apply dormant oil/lime sulphur spray. Wait until the plant is completely dormant to apply. Watch your night temperatures – dormant oil can’t be applied if we are expected to freeze.

Remember to think about spring, while you’re out there working in your yard this fall. This is the time to plant spring blooming bulbs – tulips, daffodils, crocus, hyacinth, etc.  Fall is also a great time to plant perennials, trees and shrubs. Many garden centers have inventory sales in the fall.