Lizzi Brosseau placing straw on her family garden plot, to provide cover before a storm.
Follow along with Modern Gardener’s Lizzi Brosseau as she gardens for her first time!
Just when we thought spring had passed, another stretch of cold rain and thunderstorms are back in the forecast. Even though it’s June, it’s still a good time to learn how to cover plants!
In my last post, I talked about whether or not to transplant your seedlings when temperatures are dipping into the 40s after the last frost date. Our resident expert, Jess Kemper from the University of Utah’s Edible Campus Gardens, said that it is better to transplant and cover, then to wait to transplant.
With that in mind, and our seedlings now planted into our garden plot, we’d like to cover them to protect from the cool weather ahead. Jess has given us some excellent and simple solutions for covering our plants, which I’ll “cover” in this post ;) But first, let’s talk about why your plants might need to be covered in the first place!
Clouds gathering this weekend over the Salt Lake valley. TIme to cover plants!
Why cover plants?
Many parts of the country have predictable seasons, but in Utah, it can swing from summer to winter in a matter of hours.
I asked Jess why this would be and she replied “it’s partly because of our elevation and climate change.” This makes it very important for Utah gardeners to keep the Farmer’s Almanac handy, watch the forecast, and know how to cover and protect your plants!
When cold fronts move in it’s important to cover plants from turbulent winds and heavy rain and hail that can easily damage leaves and stems. Cold temperatures in the low 50s and 40s can stunt your plants, but if temps get into the low 30s, frost will actually damage them on a cellular level. It’s similar to the effects of frostbite—the water in your plants will freeze and burst the cells of the plant. If you have tender warm-weather crops, like tomatoes or melons, covering those plants is especially important.
How will you know your plants have been frostbitten? “You’ll notice right away,” Jess says. “The leaves will turn black and fall to the ground within hours.” Yikes!
We definitely want to avoid stunted or frostbitten crops, so we’ll need to cover our plants!
Frost cloth used to cover bok choy at Top Crops in Salt Lake City.
One of the easiest ways to cover plants is frost cloth, which is a gauzy cloth that can be purchased at garden centers and hardware stores. You simply drape it over your plants at night, which keeps them insulated and protected from hail and temperatures low enough to bring on frost. Most plants don’t like the frost cloth touching them so you can use sticks and twigs to prop it up or your tomato cages.
Frost cloth is relatively inexpensive and can be reused. Once the cold weather has passed you can easily roll or fold the drop cloth and store it for next year. You’ll just want to make sure it’s completely dry before storing it.
Straw used as mulch and to cover plants in a community garden plot.
Another easy option is gently packing a thick layer of straw or mulch around your plant like you would wrapping a fluffy blanket around a napping kitten. This insulates your plants and helps with moisture control.
In Fred Montague’s book, Gardening, An Ecological Approach, (see our video on garden planning with Fred here), he recommends raking straw cover off your plant’s soil during warm, sunny hours, so that the dark soil can absorb sunlight and heat. Then, before nighttime, you can rake the straw back to cover the soil and trap the heat that the soil absorbed during the day. This is an extra step, but I thought it was a good idea and Jess loved it too!
Gallon Milk Containers
Jess also mentioned using gallon milk containers to create a mini-greenhouse for your seedlings. I’ve seen these covering plants often in many gardens. You simply cut one end off and fit the removed end over your plants. This option works especially well for small seedlings that have just been added to the garden. It insulates, diffuses harsh sunlight, protects tender leaves from hail, and it's a good way to reuse your containers!
If you don’t have a supply of gallon milk containers, hit up your favorite coffee shop, they’ll have plenty. But you’ll want to wash and sanitize them first, even if they’ve been rinsed out at the coffee shop.
Before I talk about this method of plant cover, I want to share an interesting bit of gardening regionalism…
I’m very familiar with Walls O Water because my father used them in his garden, and I remember seeing them everywhere in my neighborhood as a kid. So when my husband, who’s from the midwest, saw them in our community garden and asked me what they are, I was really surprised that he didn’t know! Jess also said she’d never seen these before moving to Utah. I never knew they weren’t used in other places! Gardening is so fun because we often learn how to garden from how our friends and neighbors garden. It’s a real community builder!
Anyway, back to Walls O Water. These look something like otter pops stapled together lengthwise into a wide band of blue or green semi-transparent plastic. The band is connected in a circle to surround the plant, and each otter-pop is filled with water which causes it to stand upright if completely filled. This creates a mini-greenhouse, like the gallon milk container method, but is sturdier and provides more insulation. They are very simple to use and relatively inexpensive. These are most often used for covering heat-loving tomato and pepper plants, because they retain so much warmth.
Low tunnels used to cover fall lettuces at SLC Top Crops.
If you’re looking for something a little more sturdy and you have the means to do it, low-tunnels with frost cloth will definitely keep your young plants warm and protected from cold snaps. This is a more involved cover option, but also a very sturdy, lasting investment. This method is especially helpful if you have a large garden or farm with many rows of crops to protect. I interviewed local farmers Elliott and Manda from Top Crops about their low tunnel method, you can see that here.
Low tunnels are a more involved cover option, but also a very sturdy, lasting investment. You can extend your growing and harvesting season well into the colder autumn months if you go this route.
Soaking straw with water will help weigh it down and provide insulation.
A Few Tips for Covering Plants on Cool Summer Nights
Here are some extra tips from Jess about preparing your plants for those exasperating swings in temperature:
Make sure your plants are adequately watered, even saturated with water, before night comes. It might seem counterintuitive, because water freezes, but frozen water will actually insulate your plant!
Secure your cover well enough to withstand windy weather, so that your hard work doesn’t blow away. You can do this with deeply set poles, stakes, wraps, and twine or even some big rocks. If you use straw or mulch to cover, saturating the mulch with water will help weigh it down and *bonus* provide extra insulation.
If your plants are portable because they are in a planter, moving them to an area of your property, like a south-facing wall, that has absorbed heat throughout the day will be helpful. The heat absorption will radiate warmth to the plants throughout the night, creating a warm microclimate for your plants!
How will the Brosseau family cover plants in their garden this year? Straw! It is available at our community garden for free, it will discourage weed growth, create more warmth for our heat-loving melons, tomatoes, and peppers, and we can leave it on for the full season to maintain these benefits. That’s a win-win situation!
Jess suggested laying the straw over our drip lines by grabbing big handfuls and placing them around our plant stems, over our full plot. After we’ve laid down the straw, we’ll give the plot a big drink, and our plants should be protected this weekend. We’ll visit them after the storms have passed next week, and let you know what happened!
Don’t forget to follow Modern Gardener on Instagram and Facebook to see my Stories about gardening, and make sure to chime in with your own! We love to learn from other gardeners, and look forward to seeing what you’re learning in the garden too!
Modern Gardener Host and Author
Lizzi works for PBS Utah as a digital producer and host of Modern Gardener. Read more