Perennial Flowers: Most perennial plants do not suffer frost damage and do not need to be covered. Frost sensitive perennials include Hostas and Bleeding Hearts. They should be covered to protect their foliage and flowers. Cover any blooming or budded up perennials.
Perennials. The newly emerged growth of most perennials can tolerate temperatures in the low 30s and upper 20s °F. This includes many early emerging perennials such as bleeding heart, daylily, catmint, and columbine. In most cases, early leaf growth on these plants will be just fine with cold temperatures.
That means that perennials typically emerge each year when the time is right. In an early spring, that time might be sooner. In a long, cold, snow-covered winter, it's typically later. At the worst, a surprise late frost might brown out some of the perennial foliage, but it won't kill the plant.
1. In order to overwinter a perennial or shrub in a container outside, it needs to be two zones hardier than the zone you live in. 2. Perennials and shrubs that are in your zone or one colder can be overwintered in an unheated garage, buried in the ground, or transplanted.
Some Hardy Perennials Need Winter Protection in the North and Midwest, and Tender Perennials Require Special Protection Methods. Many perennials hardy for your zone make it through winter just fine with no special attention.
It's common to think that everything should be chopped down to the ground in the fall, but some perennials actually need their foliage to protect new shoots through the winter. Other varieties offer up important habitat for local wildlife and some perennials provide height and interest through the winter months.
Overwintering Techniques
The general consensus seems to be that the best way to overwinter containerized perennials is to take the entire pot and bury it in the ground. This way, the roots are protected like they would be if the plants were actually planted in the garden.
Cover Plants – Protect plants from all but the hardest freeze (28°F for five hours) by covering them with sheets, towels, blankets, cardboard or a tarp. You can also invert baskets, coolers or any container with a solid bottom over plants. Cover plants before dark to trap warmer air.
Perennials NOT to Cut Back
Also, do not cut back hardy perennials like garden mums (Chrysanthemum spp.), anise hyssop (Agastache foeniculum), red-hot poker (Kniphofia uvaria), and Montauk daisy (Nipponanthemum nipponicum). Leave the foliage. It's important to protect the root crowns over winter.
If it stays cold for more than one night, can I keep my plants covered, or should I remove the coverings at some point? A. Our recommendation would be to remove the cold protection covering once temperatures are above 32 degrees.
A covered porch usually provides protection from light frost, but the garage or sun room is better for freezing temperatures. A couple days in darkness won't hurt the plant. Or move them out during the day and back in at night, if cold temperatures persist.
To know when to cover your plants, you need to know when the plants you have are susceptible to frost damage. Some frost-tender plants need to be covered as soon as the temperature hits 32°F, while others can handle lower temperatures and/or longer freezing periods.
A freeze happens when air temperature dips below 32 degrees F. The colder it gets, the more damage you'll see to annual and perennial plants. A hard freeze is usually between 28-25 degrees F, and a killing freeze is 24 degrees F and below.
Light freeze - 29° to 32° Fahrenheit will kill tender plants. Moderate freeze - 25° to 28° Fahrenheit is widely destructive to most vegetation. Severe or hard freeze - 25° Fahrenheit and colder causes heavy damage to most plants.
I did some research and found out that houseplants need to be taken indoors before overnight temperatures dip below 45 degrees. Most tropical plants suffer harm from temperatures below 40 degrees. Well, we have temperatures forecast to dip into the 40s again on Thursday and lower 40s on Friday.
When Should You Cover Plants? Cover your plants at night and remove them during the day when the temperatures rise above 32 degrees F, so that the soil can warm up again. Some outdoor plants won't survive the harsh conditions of winter, bring them inside and use these tips for caring for them through winter.
The easiest way to protect from a freeze is simply by covering plants with a sheet or a blanket. This acts like insulation, keeping warm air from the ground around the plant.
Cutting back of dead or dying top growth is the only maintenance that is needed for winter preparation. Cut the stems down to the ground, or to the basal growth if you are gardening in the warmer hardiness zones. Alternatively, the flower stems can be left to cut back in the spring.
Heated Greenhouses with Roll-up Sides
This method requires minimal fuel and results in very few plant losses. To use this method, perennial houses are heated to 50°F until all of the plants are well rooted, then the temperature is slowly decreased to 35°F so the plants will vernalize and flower in the spring.
Bury the pots or bring them inside.
Alternatively, bring the pot into an unheated, not-too-bright interior space, such as a garage or cold cellar. (It needn't be completely dark.) Lightly water the plant occasionally over the winter, just enough to make sure that the soil doesn't completely dry out.
Mulching perennial plants offers many benefits. A well-decomposed compost applied as a mulch will provide much-needed plant nutrients, possibly eliminating the need to feed the plants. Mulch is used to moderate soil temperatures, help retain soil moisture, and suppress weeds.
The rule of thumb is to add one inch of water per week for established plants. Less frequent but deep watering encourages perennials to root deeply. Perennials that are said to tolerate drought are drought tolerant only after they have become established.