Experts offer tips for perennials as summer turns to fall

By: Brian Louwers | Warren Weekly | Published September 21, 2016

 Perennial mums are hardy enough to withstand winter in the ground, provided that the roots stay protected. They feature a straighter look with medium to large flowers.

Perennial mums are hardy enough to withstand winter in the ground, provided that the roots stay protected. They feature a straighter look with medium to large flowers.

Photo by Brian Louwers

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METRO DETROIT — After the long, cold winter, maybe you gasped out loud when your perennials cracked through the soggy ground in the spring. You then probably enjoyed them all summer, as the brilliant colors changed on the landscape canvas of your yard.

With fall again in the air, experts say there are things gardeners can do to keep the show rolling a little longer, and to make sure it begins again with beauty when the snow and cold recede.

Let’s start with hardy mums, a surefire way to keep color in your yard until Thanksgiving and beyond.

“We’re mainly concentrating on mums for the fall. We grow two different types,” said Kim Normand, perennial manager at Eckert’s Greenhouse & Perennials in Sterling Heights. “We grow a perennial mum and a garden mum.”

Normand said garden mums are easily identified by their rounded shape and rainbow of available colors. They’re the most popular variety these days, and Eckert’s grows nearly 10,000 annually to meet the local demand. 

“Most of the varieties out there are garden mums. They’re not a true perennial mum,” Normand said. “If you’re going to do (planting in) pots, then the garden mums are fine. If you’re planting in the ground and you want it to come back, you may want to do perennial mums.”

Normand said garden mums placed in the ground can survive lighter Michigan winters, provided you give them a little extra protection. She recommended cutting off the spent flowers and leaving the foliage intact for the winter. Adding extra planting soil, a heavier mix than potting soil, or compost around the base of the plant will prevent heaving when the ground freezes and will help avoid potentially catastrophic root damage. 

Perennial mums, a straighter and more hardy variety, are also available and can survive in the ground over most winters if the roots stay protected. 

“The snow is actually good for them. It protects them from the bitter cold,” Normand said. “But we don’t always have it (the snow).”

Beyond mums, Normand said ornamental grasses, aster, coralbells, turtleheads and ornamental vegetables still thrive into late summer. 

Roses, she said, will even bloom well into November and require only minimum maintenance afterward. 

“Let them be,” Normand said. “Once we get into September, no more pruning, no more fertilizer. We want them to naturally slow down. Winter protection doesn’t start until after we’ve had two good frosts — usually after Thanksgiving.”

There are two options for protecting roses over the winter. Cones can be used to protect shorter varieties. For taller roses, she recommended covering the base with a good 8-10 inches of compost or planting soil. Normand said some dieback could be expected and is normal on the exposed tops of roses. 

Late summer or earlier fall also is the time to consider planting new bulbs or established perennials, provided the temperature is cooperating with seasonal norms.

“Typically, perennials should be planted by Oct. 1,” said Carol Lenchek, environmental programs coordinator at Oakland County’s Michigan State University Extension office. “By planting before Oct. 1, the plants will be able to establish themselves a little bit better. They’re  more likely to withstand winter and less likely to frost heave.”

Beyond giving transplanted plants time to take root before cold weather sets in, fall is also suitable because the cooler temperatures are less stressful for the plants and those planting them.

“If you do it early enough, fall is really a good time to plant perennials because it’s cooling off,” Lenchek said. “Typically, in the fall we get more rain. It’s also a great time to plant trees and shrubs.”

Lenchek said even late-blooming perennials can be moved in the fall if desired.

“We always say don’t move them around or divide them when they’re blooming. The reality is, you do it when you have the time,” Lenchek said. “You’re not going to kill a plant by moving it when it’s flowering.”

Lenchek said thinning established perennials is easier to do in the spring, when foliage is greatly reduced.

New perennial bulbs can be planted until the ground is frozen. However, it’s important to wait until the overnight temperature of the air and the temperature of the soil drop from summer highs to discourage growth. New bulbs planted in the fall are intended to bloom later.   

Lenchek said gardeners who do their research about specific perennial plants are more likely to achieve success. Some perennials, for example, benefit greatly from mulch placed around the base once the ground is frozen.

Resources available through the MSU Extension include a statewide garden hotline manned by master gardener volunteers from 9 a.m. to noon and from 1 to 4 p.m. Mondays through Fridays through late September, and from 9 a.m. to noon Mondays through Fridays after Oct. 1. The hotline number is (888) 678-3464. Additional information is available through the MSU Extension’s website at www.msue.anr.msu.edu.

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