Bulbs and perennials emerging from the ground do not need to be protected from sub-freezing temperatures. They are growing according to nature's schedule. You don't need to protect plants until after we've had an extended warm period.
Most newly planted young perennials will need winter protection as they will not be mature enough to handle frost.
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.
Although each plant's needs may vary and some will be more winter-hardy than others, in general about a month before the last fall frost is sufficient in giving the plant enough time to establish itself and take root.
The newly emerged growth of most perennials can tolerate temperatures in the low 30s and upper 20s Fahrenheit. Freeze damage may occur if temperatures drop into the lower 20s or teens. Most well-established perennials that have been damaged by freezing temperatures should survive.
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.
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.
You can transplant perennials anytime until the ground freezes in the fall, or wait to transplant them in the spring. Fall is an excellent time to transplant herbaceous perennials because your plants will then have three seasons to establish a good root system before hot summer weather sets in next year.
Planting. Most perennials should be planted in the fall or early spring. Fall planting gives the plant more time to become established before the start of active growth in the spring. Fall-planted perennials are usually well-established before hot weather.
Spring-blooming perennials, especially in the bare root form, are best planted early in the fall. Planting in the fall while the soil is still warm will give the roots enough time establish properly. This allows the plants to emerge from well established roots, with a stronger start, the following spring.
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 protect plants from frost, you will need to cover them to keep the moisture from freezing. While an unexpected frost can leave many gardeners scrambling to find anything to cover their tender plants; it is important to use the right materials.
Early spring blooming flowers like crocus, snowdrop, and primrose can all survive the winter, and pansies are especially resilient. Violas, hostas, heuchera, irises, lily of the valley, cyclamen, and phlox also tolerate frost and provide some visual interest, as do catmint, baptista, sedum, and peonies.
Thoroughly Water plants if it's not going to rain before the freezing temperatures arrive. It may sound illogical. However, a moist ground stays warmer than dry soil. Watering the night before the freeze comes will insulate the root structure of the grass and plants and decreases the potential for cold injury.
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.
Frost zaps many perennials back to the ground. Plants are busy storing sugars and other nutrients in their roots to sustain them through winter. To support plants through this season of transition, make sure they get adequate water until the ground freezes.
Water and Feed Your Perennials
Young perennial plants may be hardy, but they still need plenty of water and nutrients to get established in the soil. You can easily water and feed at the same time with Miracle-Gro® Liquafeed®.
Spring Perennial Plantings:
Week 1: Every day to every other day. Weeks 2-3: Water 2-3 times per week, depending on environmental conditions. Weeks 4+: Water 2-3 times per week, more in hot/dry conditions.
Morning watering is actually preferable to evening watering as the plant has time to dry before the sun goes down. At night, water tends to rest in the soil, around the roots, and on the foliage, which encourages rot, fungal growth, and insects.
Once planted, perennials come back each year. Depending on the type of plant you've planted, they can live anywhere from 3 to 15 years! While you can always dig them up and re-plant, it's usually best to pick a plant type that you can see yourself living with for a few seasons in your garden.
Many gardeners are hesitant to try starting perennials by seed because of the notion that you will not get to enjoy the flowers the first year. This is true for some perennials, but if you sow seeds for the perennials on this list early in the season, they will reward you by flowering within the same year.
In most cases, plants appreciate being fed in early spring, before the growth spurt begins. In general, fertilization of in ground plants with a slow release product after mid-July isn't recommended. After midsummer, plants need time to completely harden off before fall and winter.
Once temperatures drop below 40°F, you may want to start covering your plants with a frost blanket depending on what you're growing, which we'll get into in just a bit. Freeze – A freeze is when the air temperature is 32°F or below.
If you're wondering at what temperature threshold you should be bringing your plants, there's a short answer: when nighttime temperatures reach 45 degrees (F), it's time to bring your plants indoors.