"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 winter 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. For example, here in Georgia we wait to prune hardy lantana until new growth begins to emerge in spring as fall pruning almost always causes death of the plant. While some perennial plants are super cold hardy others might be a little on the tender side. Too, you never know how severe any given winter will be, so it's best to be safe than sorry when it comes to winterizing your perennial garden.
So you're here reading this article because many if not all of the perennial plants in your garden or in the landscape have or are starting to go dormant in your gardens 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 totally kills off the top foliage of the plant.
Non-Dormant Perennials - During the fall, if perennials still have some green, living foliage, they might still require some water. In the absence of rainfall, give the plants a good deep soaking every week or so. 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 (leaves have truned brown) during the fall or early winter. That being said, I and many other gardeners usually wait until late winter, when we're pruning our roses, crape myrtles and many other plants, to cut dormant perennials back. That being said, I'm one of those who doesn't mind the look of dormant perennials during winter. If you'd rather cut plants back right after they've gone dormant it's okay to do so.
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 when and how 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 insulates and protects the roots of plants if and when some seriously cold temperatures come. Compost or shredded bark (when it decomposes) will also add 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 straw or shredded wood 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. Where I'm at in central Georgia the average first frost date is November 9th, so I discontinue feeding perennials in mid-September. That being said, as mentioned above, a layer of compost that plants will feed off of as needed is okay.
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.