"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.
Here in the Southeast, by late October we can have our first frost any night. A light frost will kill off many annual plants but won't harm most hardy perennial plants. But, when the first light frost comes, we know the hard frosts and freezes will follow sooner or later.
Winterizing Tips
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 and rainfall amounts. 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 soil moisture until a hard freeze kills off the top foliage of the plant. If it's not raining 1 to 2 inches of water perennials that still have live foliage will require some supplemental irrigation. 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.
Pruning & Deadheading
If you haven't been deadheading your annuals and perennials as needed throughout the growing season, it is time to start. Deadheading is the practice of trimming off the dead flowers of a plant, but leaving the foliage to continue to grow and feed the roots. In the South, by November some perennials have gone completely dormant while others still have green foliage and might even be producing flowers, such as Anemones.
Dormant Perennials - Regarding dormant perennials (foliage has gone completely brown), you can cut MOST of these back to the ground when they have gone completely dormant in fall. That being said, and because most southern gardeners have perennial varieties of lantana planted in the gardens, DO NOT prune your perennial lantana plants back until new growth begins to emerge in spring. Fall pruning of lantana almost insures death of the plant.
Non-dormant Perennials - Regarding those perennials that still have some green growth and might still be in flower, you can keep these deadheaded until they go dormant. 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. Consult with your local nurseryman, Master Gardener, or other perennial expert for the best times to deadhead individual types perennials.
Mulching
Durng summer, the benefits of mulching your perennial plants with a shredded bark product are fairly obvious. It shades the area of soil above the roots of the plant, allowing the ground beneath to remain cool and moist for a longer period of time. In the heat of the summer this is especially good for perennials, but at other times of the year mulch is very important as well. In the winter it gives extra protection from freezing temperatures that can harm the roots of plants either by simply being too cold for them, or the process called frost heave, where constant freezing and thawing can actually pry some root masses right up out of the ground. Finally, as shredded bark decomposes, it adds organic matter to the soil. Your plants will appreciate this nutrient-rich meal and reward you with better performance during the next growing season!
Moving & Dividing Perennials
While many container-grown perennial plants can be planted most any time of year in the Southeast, many established perennials growing in your garden are generally best moved and divided in spring or summer, depending on the variety. A couple of exceptions are iris (divide in mid- to late summer) and spring flowering bulbs such as daffodils, etc.. Do some research or consult with your local nurserymen, Master Gardener, or other perennial experts to determine when to transplant a particular type of perennial plant. Keep in mind that the best time to move an established perennial is the same as the recommended time for division.
