My neighbor leaned over the fence and nodded at the purple asters in my back border. He told me they would never make it through the cold, not after the first hard freeze. The next fall the same clump came back fuller than before, and he just shook his head and walked off.
Whether fall plants come back every year depends on one thing. The plant has to be a hardy perennial, which means its roots survive winter and push out fresh growth each spring. True perennial fall flowers like asters return on their own, while other fall bloomers die for good once the cold sets in.
So you really have two camps of fall flowers, and you want to know which one you are buying. Hardy perennials store energy in their roots and crowns through winter. The top growth dies back, but the living roots wait under the soil and send up new shoots when your weather warms. A plant rated for your winter low will do this for you for years.
The other camp can't handle a freeze. These plants have no cold-hardy root system to fall back on. When your ground freezes solid, the roots die with the leaves and the plant is gone. You start over with a new one each spring, the same way you would with a tomato in your vegetable bed.
A few fall favorites come back like clockwork in cold zones. Asters, goldenrod, sedum, and Russian sage are reliable perennials that return from their roots year after year. Plant them once and they settle in, spread a little, and bloom every fall with almost no help from you. If you want a garden that fills in on its own, these four are your backbone, and they will save you the cost of replanting each spring.
Plenty of showy fall plants do not. Dahlias die in the ground once it freezes, so cold-zone gardeners dig the tubers and store them indoors over winter. Strawflower is a true annual that finishes its whole life in one season. And most florist mums, the cheap potted ones sold by the door each fall, are bred for one big show and rarely survive a real winter outside.
Those last three are tender fall plants, and the label matters when you stand at the garden center. A plant tag tells you the lowest temperature it can take, given as a hardiness zone. If your winter drops below that number, the plant will not come back for you, no matter how healthy it looks the day you buy it. You can still grow tender plants on purpose, as long as you know going in that you are buying them for one season.
Read the plant tag before you buy and match its hardiness zone to your own. A plant rated colder than your winter low will come back.
Get perennials in the ground at least six weeks before the first hard freeze so the roots settle in while the soil is still warm.
Soak new plants well through fall, since strong roots going into winter are what bring the plant back the next year.
Spread two to three inches of mulch over the crown after the ground cools to guard the roots from hard freeze and thaw cycles.
Do these few things and your hardy fall flowers will return on their own. Asters, goldenrod, sedum, and Russian sage ask for little once they take hold. Check the tag, plant early, and skip the tender ones if you want a garden that comes back. My asters have returned six falls running, and my neighbor stopped doubting them years ago.
Read the full article: Fall Blooming Plants: A Complete Guide
