Does This Blanket Make My Blooms Look Big?
Protecting your plants from cold weather
by John Toborg, Field Services Manager
As we approach that time of year many of us look forward to after toiling outside during the oppressive heat and humidity of summer, we can’t forget about those that don’t necessarily look forward to this cooler season – those tender perennials, those colorful tropical dotting our landscape, those delicate annual flowers that line our patios and those flowering shrubs outlining our backyards.
While most native plants, and even some non-native plants, can withstand freezing temperatures, even into the 20s, many plants in our landscapes can suffer damage with temperatures in the low 40s. When freezing temperatures or frosts are forecasted, you should cover those plants.
But what is the best way to cover plants, and how do you choose which one to cover? Let’s not jump too far ahead.
First, it is essential to keep your landscape as healthy as possible throughout the year; so it is better prepared for these challenging days ahead. Meeting watering needs, as well as nutritional ones, is vital to ensure fully thriving plants. Healthy plants can withstand cold temperatures and recover from injury better than unhealthy or stressed plants. Typical landscape ornamentals should be fertilized 3-4 times per year. However, be cautious when fertilizing late in the year as this will encourage a new flush of growth which will be more susceptible to freeze damage. Just as late fertilization causes a flush of growth so does late-year pruning. Therefore, you should avoid late summer or fall pruning. Also, it is vital to water thoroughly during dry spells to keep your landscape healthy.
One should also consider site selection when planning your landscape. Yes, even your yard will have microclimates. You probably have a low-lying area somewhere in your yard – cold air will settle here, so it’s not a good idea to place cold-sensitive plants in this area. You may also have a high and dry spot where you would not want to create a wind barrier to protect these exposed plants. Although a tree canopy will trap radiating heat at night and keep the area beneath warmer than surrounding areas, growing plants that prefer full sun under the shade of a tree will only result in sparsely foliated, stressed, unhealthy plants.
Now that your landscape is flourishing and is as healthy, well-planned, and thoughtful as you could possibly make it, Mother Nature is getting down into the 20’ – 30s!!!
It is a good idea to be sure your landscape is well-watered the day before a freeze is in the forecast. Wet soil absorbs more heat during the day and will radiate that heat at night. A 2”-3” layer of mulch also reduces radiant heat loss and protects plant roots. After you’ve thoroughly watered your landscape and as late in the day as possible to allow the soil to absorb the sun’s heat, it’s time to get out the blankets, painter’s drop cloths, thick sheets, or newspapers, or burlap - Anything that allows air and sun to flow through. Most landscape supply stores also sell frost cloth in varying thicknesses. Just stay away from plastic tablecloths, shower curtains, etc., which do not breathe and can damage leaves if they touch them. Double-check the clothes are laid over the plants and extend to the ground. It will trap the heat as it radiates. Coverings protect more from frost than from extreme cold, but creating this sealed air pocket will help hold heat around the plants. On windier nights, it is a good idea to anchor these clothes to the ground with pins, bricks, rocks, etc. Some people even include an incandescent light bulb to generate even more heat under the covering. Just be careful not to allow it to burn foliage.
For those cold-sensitive palms in your landscape, it is vital to wrap the entire head of the palm including the bud and fronds. The bud is the heart of the palm and must be completely protected. Secure the cloth around the head of the palm with twine, clothes pins, or clips. Also, work down the trunk of the palm to the ground. The ground will project heat to the palm.
The morning after …
Once temperatures rise and frost dissipates, coverings can come off. However, there is little danger of leaving the cloth on if there is a chance it could freeze again.
Unfortunately, you come to realize, despite your best efforts, Mother Nature left you with some pretty ugly plants here and there. Your first thought is to get out the pruning shears and hack away. STOP! Put them back in the shed!
Remember, pruning will promote new growth, and this new growth will be even more susceptible to freeze damage. Have patience and wait until the first full moon in March, when spring should be well underway. Apply your spring fertilizer, prune off dead tips, and wait for your landscape to push out a new coat of lush, green leaves.
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