"My perennial plant didn't survive the winter. What happened?" I hear this every spring from both long-time and beginner gardeners alike who visit our nursery and garden center. So, I want to address some issues that can help improve the survival rate of your perennial plants. Keep in mind that it's important to know the winterization needs of each specific variety of plant in your garden.
If you live in a region that experiences freezing temperatures during the winter, chances are you're here because many if not all of the perennial plants in your garden or in the landscape have gone dormant and are looking pretty ugly. So, what to do? Should the ugly dead foliage be cut back? If so, when? Do the plants still need water? If and when should plants be fertilized? Read on to find some helpful tips for winterizing your perennials.
Don't Forget To Water!
Water is very important. Once temperatures cool off in the fall it is natural to assume that your perennials don't need water. This may or may not be the case and depends on the type of plant, rainfall amounts, and whether or not the a plant has gone completely dormant. True, cooler temps mean the plants do not transpire as heavily as they did during the heat of the summer, but they continue to need water until a hard freeze kills off the top foliage of the plant.
Non-Dormant Perennials - During the fall, if perennials still have some gree/live foliage, they'll still require some water in the absence of rainfall. Give the plants a good deep soaking every week or so during dry weather. The best way to check whether or not your plants need water is to touch the soil around the root zone at the soil surface and a few inches down. If it feels moist, do not water. If it feels dry, water enough to soak the entire root mass. Like a good rain, a good soaking will usually last a week or two in fall, depending on the temperatures.
Dormant Perennials - Perennials that have gone totally dormant (lost all their leaves or have died back) won't require much if any supplemental water during the winter. That being said, if the soil becomes very dry during periods of prolonged dry weather, it's good idea to deep soak the soil around the roots every two weeks or so, and especially if a hard freeze is forecast. Dry roots are highly susceptible to freeze damage. On the other hand, if there's moisture in the soil it will form an ice sheath around the roots protecting them at 32 degrees F.
Pruning & Deadheading
Though not necessary, to clean up the garden, most perennials can be cut back after having gone dormant (lost all their leaves) during the fall or early winter. That being said, I usually wait until late winter, when I'm also pruning roses, crape myrtles and many othe plants, to cut most of my dormant perennials back. But I'm one of those who doesn't mind the look of dormant perennials during winter.
Dormant Perennials - If you are allowing some perennials to reseed themselves, it's a good idea to wait to cut these dormant plants back until you've collected the seed or the seeds have dropped naturally. Otherwise, most perennials that have gone completely dormant (foliage has gone completely brown) can be cut back to the ground or just above the ground. That being said, DO NOT prune perennial Lantana back until new growth begins to emerge in spring. Fall pruning of lantana almost always causes death of the plant. Instead, wait until new growth begins to emerge in spring before removing dead branches from Lantana.
Non-Dormant Perennials - Perennials that still have some green growth and/or are producing flowers should not be cut back until they've gone completely dormant. You can keep these deadheaded until they go dormant. "deadheading" is simply the removal of spent flowers. A good general rule of thumb for deadheading: if it looks dead, cut it off. Make your cuts just beyond/below the dead part of the flower or stem. The best reason to do this is that the plants (and your gardens) look so much better with all the dead flowers, stems and foliage removed. It also adds to plant health because the plants will put more energy into making seed at the expense of vigorous leaves and roots if they are not deadheaded. This being said, if there are perennials that you want to go to seed, wait to prune until after you've collected the seed.
NOTE: If you are unsure as to how and wehn to prune a specific variety of perennial plant always consult with your local nursery and garden center professional or just ask about it in Ask Experts here in Gardenality.
The benefits of mulching your perennial plants with a shredded bark or compost during summer are fairly obvious. It helps to hold in moisture and keeps the soil cooler. But mulching around perennial plants during the winter is important as well because it provides extra protection from freezing temperatures that could be damaging to roots. Additionally, as shredded bark decomposes it adds beneficial organic matter to the soil. Your plants will appreciate this nutrient-rich meal and reward you with better performance during the next growing season.
Apply mulch or compost at a depth of 1 to 2 inches for most perennials. Tender perennials, such as elephant ears, can be protected with a heavier layer of mulch (4-6 inches) that can be removed in early spring to allow new growth to emerge.
During the dormant season no feeding of perennial plants is necessary. In fact, in cold-winter areas you want to discontinue fertilization of perennial plants at least two months prior to the average first-frost date in your area. That being said, you can mulch perennials in fall with an organic compost, or your own home made compost. Doing so will feed the soil in your garden and in turn feed your plants come next spring!
Moving & Dividing Plants
Where I garden in the South, it's a general rule of thumb to divide spring and summer blooming perennials in the fall, and fall bloomers in spring. Keep in mind that the best time to move an established perennial is the same as the recommended time for division. If you are unsure as to when to divide a specific type of perennial consult with your local nursery and garden center professional or just ask about it in Ask Experts here in Gardenality.
Storing Tender Bulbs
Some of us grow some tender perennials among the more hardy perennials in our gardens. Many of these tender perennials can be dug and stored for the winter and replanted in spring. After the first frost has struck, and foliage begins to yellow and die, cut back the foliage, dig, and store tender perennial bulbs such as dahlias and gladiolus. Store bulbs in a paper bag in a cool, dark space. When digging, be careful not to damage the underground bulb or tuber.