Log entry, June 9, 2014: Disappointment and incredulity at chilling temperatures so late in spring just made us realize that, once again, Colorado is a tough (but beautiful) place to grow anything. Why is it that one pepper plant stands tall and the next is decimated to the ground? A whole row of newly planted, grown-from-seed heirloom tomatoes lay bent over in my garden, wilted by the cold. Their leaves were shriveled and dead. On the evening of June 9, the temperature dropped to 36 degrees in parts of Fort Collins. Other areas outside city limits dropped to freezing. Regardless, the cold temperatures did a number on warm season vegetable plants.
By Susan Roseveare
Colorado State University Extension Master Gardener in Larimer County
The chilly air that hit the Front Range three weeks after the last supposed frost date shocked most avid gardeners. “No!” said one. “It can’t be!” said another. “If only I’d put a cover over the plants!” was my thought.
The cold temperatures were so unexpected, and since my garden is 1/3 of an acre, what would I choose to cover? Had we only known “it” was coming (that chilling frost), we could have employed a myriad of techniques to protect our fledgling plants.
Let’s talk about some of those techniques. Row covers can be a Colorado gardener’s best friend. With our daily fluctuating temperatures, row covers can help protect tender plants. My grandma used to throw an old sheet on top of the garden if there was a chance of a freeze or frost. When I was little, I remember my mother and me tying a blanket around the lilac bush hoping to preserve the buds from being frozen in anticipation of the celebration of spring.
Manufactured row covers can be anything from a light gauzy material to a plastic sheet or tarp. The light gauzy row cover can serve multiple purposes. It can protect from frost, shade from the sun and protect from chewing, crunching insects that find your garden plants too delectable to resist. Another type of row cover, commonly referred to as “seasonal extensions” usually come as a type of clear plastic sheets, formed around screens or hoops that protect the garden and can raise the ambient temperature 3 to 6 degrees F, as well as maintain soil temperature and extend the season both in the spring and in the fall.
Walls of water have been around for years. By placing one of these around a plant and filling the tubes with water, it not only provides insulation from the wind and chilling frosts, but if the water cools and freezes, it can release heat as it thaws and protect the plant.
My personal experience involves throwing just about anything over a plant that I can, including mulch. I’ve used tarps, blankets, trash bags and anything in a sheet form. I currently have black fabric on the ground for my peppers and tomatoes with tires around a select few. Some of my plants were damaged, but by cutting them back (I saw a sprig of green near the base), I hope they will recover.
Another interesting “row cover” that nature provided this year was an early spring rain that turned to snow. The rain froze over the lilac buds before it began to snow. This encapsulated the buds, preventing freezing, and the subsequent snow insulated them and kept them from freezing. As the snow and ice melted, the thermal heat released by the melting ice kept the buds from freezing. Growers in the southern states employ this method to keep the citrus crops from freezing. Nursery growers do this as well.
If we had only known the killing frost was coming, a simple toss of the blanket, a wall of water, and/or a little mulch might have saved some plants. For more information on row covers and seasonal extensions, as well as recommended planting dates, check out the CSU Master Gardener website for Garden Notes #722 (season extensions), Garden Notes #740 (frost dates), Garden Notes #720 (vegetable planting guide) from www.cmg.colostate.edu and PlantTalk #2018 (spring frosts) and #2013 (frost free dates) from www.planttalk.org.