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Fall Planting: Things to Know Before You Grow

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Fall is a great time to prepare for next year’s gardens. Learn from the local experts on what to plant and how to plant it, for beautiful results next year.

Beech Tree

We think of spring as planting season, but autumn is an ideal time to plant nearly anything. Most trees, shrubs and perennials thrive as well as or better when planted in fall than in spring. For one thing, they don’t have to battle the heat and dryness of summer, while they establish roots. In fact, most trees can be planted right up until the ground freezes.

There are other benefits, too, such as lower prices and less-harried greenhouse workers.

“From a nursery’s standpoint, we have more time to spend with customers in fall, because we’re not so busy doing everything we have to do in springtime,” says Jon Carlson, owner of J. Carlson Growers, 8938 Newburg Road, Rockford. “And the roots of plants, shrubs and trees are very active in autumn, right about the time their tops start to look dormant.”

“From a price standpoint, it’s a great time to plant, because most places have half-price sales,” says Michelle Branstiter, store manager at Village Green’s 2640 N. Main St. location in Rockford. “The selection may not be as wide, because we sell out of some things, but fall is a reliable time of year to plant perennials. While you’re at it, if you’re out planting mums or perennials, why not make a larger hole and throw in some spring bulbs? Fall is the only time you can plant most spring-blooming bulbs, like daffodils and tulips. They need the cold winter to force their blooms in springtime.”

Naturally, most annuals should be planted in spring, because they’ll likely die at the first major frost. But most spring-blooming perennials do better when planted in fall.

“There’s a general rule of thumb that if a perennial blooms in the spring, it’s best to plant it in the fall, and visa versa,” says Dee Speaker, greenhouse perennial manager at K&W Greenery, 1328 Hwy. 14 East, Janesville, Wis. “But plenty of people are successful at dividing fall-blooming plants in fall, too. You just have to be more careful.”

Fall is also a great time to divide your existing perennials.

“It’s best to finish dividing or transplanting your perennials about six weeks before frost, so aim to be done by the end of September,” advises Speaker. “Cooler weather is better for dividing, because the heat is hard on plants, even when you’re not disturbing their roots. After you dig a hole in the new location, add some mushroom compost or other nutrients. After you plant, be sure to water well.”

Watering sounds so simple, but a lot of folks get it wrong.

“The best way to water is gently, with a constant trickle from a regular hose,” says Carlson. “I just lay it down by the dripline of the tree and let water soak in. I’ve seen people plant new trees, then blast them with a powerful nozzle, which just disperses the water where you don’t need it. Slow down a little.”

Branstiter recommends using a root stimulator product while planting. “It’s made specifically to get the roots going faster, so they can get established before the ground freezes,” she explains. “If you plant in fall, plants only have to get through a few more weeks before they can go dormant for the winter. Then they’re ready to wake up and grow in springtime. Fall is an easy time of year to plant.”

One disadvantage to dividing perennials in fall is that they’re larger and heavier to handle after a season’s growth.

“You can cut things back in the fall, before dividing,” says Speaker. “That won’t hurt them.”

Don’t forget to move your container perennials into the ground, too, so they can survive the winter. “Very few things can survive unless they’re in the ground,” says Speaker.

The life of annual plants can be extended by covering them with a lightweight sheet in the evening, when you hear frost is expected. “Covering them up is best, but another trick we use, for hard-to-reach containers or very large areas, is to go out before daybreak and spray them with the hose,” says Branstiter. “Washing away the frost before sunlight hits it is less shocking to the plant.”

Although J. Carlson Growers plants some trees right up until the ground freezes, a few varieties are best planted in springtime, such as larch, bald cypress and eastern redbud. When in doubt, ask.

Fall Favorites

The following are among reliable plants that add interest to your fall garden.

Aster – “Who can resist these, especially the purple aster?” says Branstiter. These perennials are much easier to grow than mums, and offer both gorgeous color and much-needed food to pollinators and other wildlife, during autumn. In the past, many varieties were vulnerable to powdery mildew. Sandra Mason, a horticulture educator with the University of Illinois extension service, recommends the following cultivars, selected for disease resistance: ‘Alma Potschke’ (3 feet tall, brilliant pink); ‘Honeysong Pink’ (3 feet tall, pink); ‘Purple Dome’ (2-2.5 feet tall mound, deep purple); ‘Red Star’ (1-1.5 feet tall, deep rosy red); ‘September Beauty’ (3.5 feet tall, deep red); and ‘September Ruby’ (3-4 feet tall, deep rosy-red blooms).

Coral Bells (Heuchara) – The variety available in this plant has exploded in recent years. Good choices for fall interest include Buttered Rum, Crimson Curls and Beaujolais.

Hardy Hibiscus – These happy showstoppers, some with plate-sized blooms, couldn’t be more cheerful. There are many reliable varieties. Their cousin, the Rose of Sharon, is even hardier and can be grown in a tree form, a less weedy-looking structure.

Grasses – Both hardy and annual grasses can play a starring role in fall landscapes. Speaker is a fan of purple fountain grass ‘Vertigo,’ and its brighter pink cousin, ‘Fireworks.’ “Even though they aren’t hardy, they grow large in one season and look attractive right up until it snows.”

Proven Winners is touting two switch grasses, called ‘Cheyenne Sky’ and ‘Dust Devil,’ for their compact forms and hardiness in zones 4-9. Three-foot-tall Cheyenne Sky starts out green, turns wine-red by fall, and provides good cover for birds in winter. Dust Devil is a foot taller and has bluish-green leaves tipped with burgundy in fall. Branstiter recommends planting a base of hardy grasses, and throwing in a few clumps of the more showy and colorful annual grasses. “‘Karl Foerster’ is a really nice, hardy clumping green grass that sends up reddish-bronze wheat-like seed heads in fall,” she says. “Most commercial properties incorporate it into their landscapes because it’s attractive but requires almost no maintenance.”

Sedum – Sturdy sedums pop up reliably each spring and come into full glory in fall, when their green heads transition to shades of pink and burgundy. There are white and lavender varieties, too. Popular varieties include ‘Pure Joy,’ ‘Autumn Joy,’ ‘Garnet Brocade,’ ‘Maestro,’ and ‘Neon.’ Sedums are succulents, so don’t overwater.

Hydrangeas – These no-fuss shrubs add big flowers to your garden through summer and fall. “Some varieties are white all summer, then turn pink or bronze in fall,” says Branstiter. “‘Blushing Bride,’ ‘Limelight’ and ‘Little Limelight’ are all good picks.”

Daylillies – There are hundreds of varieties of daylilies, and scores of them are late-blooming, some right up to frost. They span the color wheel from white and yellow to purple, red and orange. Three beauties are the scarlet Chewonki, orange-red Dune Dumpling, which has a double bloom, and dramatic mulberry ‘Water Dragon.”

Euonymous (Burning Bush) – Perhaps no plant says “fall” quite like a burning bush shrub. Two newer ones are ‘Fire Ball’ and ‘Unforgettable Fire,’ bred for smaller spaces. Plant in full sun and fertilize each spring.

Cold-Resistant Annuals

These plants won’t survive winter, but will put up with cooler temps longer than most.

Pansies: New flats of these sweet-faced flowers appear in greenhouses in September and will return in very early spring.

Calibrachoa (Proven Winners Million Bells): They look like mini-petunias, and “Many varieties can handle a light frost,” says Branstiter. Keep that in mind when selecting plants next spring.

Ornamental Cabbage and Kale: Lovely, but don’t eat it. “Remember that ornamental plants may be grown with fungicides, pesticides and other non-food standard chemicals,” says Branstiter.

Thoughts on Trees

Jon Carlson strongly believes that homeowners should think carefully about their planting space before choosing a tree or shrub. “Remember, they grow,” he says. Don’t ask a large tree to thrive in a cramped space or a shrub to fight the wrong light and moisture conditions. If you’re confused, ask questions. “Part of our job is to educate,” says Carlson. “We try to help people make a good selection for their particular conditions.”

Here are just a few conifers and trees that Carlson finds interesting.

Wintergreen Arborvitae
Ever notice how snow-laden arborvitae often split into pieces? This kind has a main dominant trunk, which prevents winter damage, and the same lovely dark-green foliage we love to see year-round.

Weeping Blue Alaskan Cedar
This narrow, pendulous tree has bluish foliage and can grow 50 feet tall. Lovely alone or planted in small groupings, if you have ample space.

Dawn Redwood
Once thought to be extinct, this interesting tree was re-discovered in 1945 in China, and offers light-green spring foliage that turns peachy bronze in fall.

Weeping White Spruce
A wonderful narrow specimen tree with gray/green needles, an upright leader (trunk) and pendulous side branches.

A few years ago, ComEd asked Carlson to recommend lower-growing trees that are more compatible with power lines than their giant counterparts. He named the following “utilitrees:”

Serviceberry: Attractive year-round, with white spring flowers, orange-yellow fall leaves and berries that nourish wildlife.
Eastern Redbud: Usually has multiple trunks, ascending branches and reddish-purple spring flowers, with yellow fall foliage.
Japanese Tree Lilac: Highly tolerant of urban streets and salt; large, creamy-white spring flowers.
Amur Maple: Glossy, deep-green leaves, and great fall foliage.
Susan Magnolia: Early blooming large spring blossoms, and tops out at 20 feet.
Japanese Red Maple: Beautiful color, spring through fall.
Hawthorn: Attractive flowers, fruit and shape. “Crimson Cloud” and “Thornless Cockspur” are smaller varieties.
Pagoda Dogwood: Attrative year-round, with creamy spring flowers and blue fruit on red stems.

Mum’s the Word

Yes, a hardy variety of “garden” chrysanthemums (mums) can survive our winters, and many do. Their track record is so spotty, though, that local greenhouses consider all mums to be annuals. Never expect “florist” mums to live through the winter; they’re grown to produce large flowers, not the underground stolons (like a root) that they need to survive cold weather.

A relatively new form is the profuse Belgian Mum, labeled for USDA hardiness zones 4 through 9; we’re on the borderline of zone 4/5 in northern Illinois/southern Wisconsin.

“We only carry the Belgian mums,” says Michelle Branstiter of Village Green. “Some people have very good luck holding mums over from year to year, and some people don’t. To increase your odds, plant them near the house, mulch them, and plant them with some root stimulator, to help them get established before it’s cold. But don’t count on them making it.”

Dee Speaker of K & W concurs. “If you get them in the ground now, in full sun, and they have good drainage, and you keep them watered through October – but not too much, they don’t like wet feet – they might make it. Putting mulch around them, after the ground freezes, won’t hurt, but it doesn’t guarantee their survival.”

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