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.
Wind down the water as temperatures begin to drop below 40 degrees. Most summer annual plants will freeze and die with the first or second hard frost. As always, irrigate your perennials and annuals in the morning when you can! That way, the soil has time to soak it all in before temperatures drop in the evening.
Keep the base of plants free of dead leaves and debris particularly before frost. Keep watering until the ground freezes. This is the most important factor for how plants weather the winter. Apply a layer of mulch or mulched leaves in late fall.
Throughout the winter your plant is still going to need some water. If the soil gets completely dry, the plant can die of desiccation. While regular watering isn't necessary, monitor the moisture level and water if the soil is dry.
Some perennials, like hostas, peonies and daylilies, need to be pruned in fall to avoid winter damage. Plants like these should be pruned after the first few frosts in late fall or early winter. Other perennials like mums and coneflowers are better off being pruned in spring just before new growth comes in.
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.
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.
If the soil is dry and the cold front is not preceded by rainfall, water the landscape before the freeze. Watering 24 to 48 hours before the freeze will elevate the night temperatures by 2 degrees. Don't overdo it. A soggy soil is not healthy for plant roots and will create root disease problems down the line.
Cold weather prep for plants in winter
Drought-stressed plants are more susceptible to cold damage, so watering plants a few days in advance of a cold snap is beneficial. Watering just before the freeze can help too by creating warmth, and the water loses its heat slowly over the hours into the colder temperatures.
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.
Most perennial plants go into a state of dormancy, or winter rest, as a result of the cold temperatures and shorter daylight hours of winter. These sleeping plants lose their stems and leaves and are dormant, not dead! They will re-grow from their roots with the arrival of spring.
Creating Watering Schedules for Winter Gardening
Try watering at mid-day — when temperatures are higher—so it can soak in before it freezes at night. Water your landscape once or twice per month from November to April. New roots form in the months of March and April. It is most critical to water during these months.
Avoid watering when temperatures are below 40°F or when sustained freezing temperatures are expected within 24 hours as this water will freeze and not be available to the plants.
Watering. Soak the plants immediately after planting and check regularly to prevent drying out. 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.
When To Stop Watering Plants in Fall. When the air and soil temperatures consistently fall below 40 F, it's time to stop watering. The ground can't absorb water once the top few inches freeze. Continue to water your plants up until this point so they're as well-hydrated as possible going into winter.
Farmers spray water before an overnight freeze because water produces latent heat when it freezes. The sprayed water on the surface of the plant will be converted to ice, and the heat trapped in it will insulate the plant from the cold environment.
Young or newly planted trees are much more susceptible to drought injury during the winter months. Make sure they are well watered through the summer and fall up until the ground freezes, and water every couple of weeks during the winter when there is no snow cover.
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.
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.
Cutting back perennials in the fall is not only a great way to keep flowerbeds looking neat and tidy through winter, but it also aids greatly in keeping plants vibrant and blooming the following year. Removing spent foliage and blooms helps a plant focus on recharging it's roots and resources.