Plantageddon: What to Do to Protect Your Spring Flowers From Frost
This has been the year without a winter for just about everybody in the country except the Pacific Northwest. Depending on where you live, February felt like April or May. When people walk around in short sleeves in February and turn on the AC to sleep at night, you know something ain't right.
Trees, shrubs, and bulbs that shouldn't be blooming for two to three more weeks are in full bloom now. Forsythias, azaleas, Japanese magnolia, flowering quince, camellias, spirea, fruit trees, daffodils, hyacinths, and more think it's spring. But spring doesn't officially begin until the vernal equinox on March 20 and your last spring frost may be a month or more after that. Should you panic that a Siberian Express may arrive before then and devastate your early bloomers?
Grumpy's advice—chill out (Great pun. Thank you). Plants blooming before we think they should happens practically every year. And our warming climate means that spring comes earlier and fall arrives latter than they did a few decades ago. You can't change it. You just have to accept it, pour yourself a glass of wine, and move on.
A hard freeze will adversely affect three classes of plants right now. Some you can protect. Some you can't. Let's discuss.
Class 1. Early blooming trees, shrubs, and bulbs. These plants are genetically temperature-sensitive. If they go through a winter and then experience 7-10 days of temps in the 70s, they're gonna bloom. You can't stop it. Unless they're low-growing and you can pile leaves and pine straw or lay shade cloth atop them, protection isn't practical. I've seen some folks cover their magnolias and camellias with blankets. To me, a yard full of blankets makes it look like you just got evicted. Before doing anything, check the expected low temperature for the next couple of nights. Most flowers can take a light frost with temps between 32-35 degrees. A hard freeze with temps of 28 or lower will kill the flowers (but not the plants). If you have beautiful spring flowers in your garden and you hear a hard freeze is in the offing, cut branches and stems with flowers, put them in vases with water, and enjoy spring inside.
Class 2. Summer vegetable plants and annuals. Mild, sunny days in late winter tempt us to get a head start on planting for summer color and harvest, but curb your impatience. Most such plants, such as tomatoes, peppers, squash, marigolds, coleus, and impatiens, have zero frost tolerance. Just a few hours of frost turn them to mush. Don't plant until after the average date of the last spring frost where you live. Don't know the date? It's easy to find. Just Google "last spring frost" and add your zip code. Voila! Now you know when it's safe to plant (or should be—the last spring frost date where I live is April Fool's Day.)
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Class 3. Tropical or houseplants. Plants like Chinese hibiscus, peace lily, mandevilla, croton, angelwing begonias, and bromeliads that you've cooped up in the dim light of the house or garage since October appreciate the sun and rain that unseasonably mild winter days can afford them outdoors. Just remember they won't take frost. Keep them close at hand so you can quickly retrieve them if real winter briefly returns.