Gardening Sweet Spots
By Donna Hessel
Every year in late September, I purchase half a dozen pots of mums to use in fall arrangements in containers. When there’s no doubt winter is settling in, I replant them in the garden, mulch them after a frost kills the flowers and hope to see new sprouts in the spring. But come spring, there are only piles of mush. No new growth to be seen. So what’s the secret to getting mums to rebloom every year?
The secret is to plant hardy, perennial mums in the garden (or containers) in mid-May or in the fall at least six weeks before the first frost. The best shops in which to find perennial mums in the spring or late summer are independent nurseries. Or, you can order seeds or seedlings from a garden catalog. The big box store garden departments tend to focus on the button mum varieties that provide a wide range of color but are grown as annuals and will not overwinter.
Varieties of Hardy Chrysanthemums
When you plant perennial mums, you’ll have lots of flower shapes and colors from which to choose. Horticulturalists generally categorize garden mums by flower shape. So look for these to provide variety in your gardens and containers:
- Anemone: One or more rows of petals with a cushion-like center
- Pompom: Familiar globular shape
- Regular incurve: Petals curve up and in, forming a sphere
- Single or daisy: Looks like its cousin, the daisy
- Spider: Long, curled petals droop down and give a spider-like look
- Cushion: Shorter, mounding varieties
If you are ordering from a catalog, look for some of these names:
- ‘Clara Curtis’ – a long-lasting variety that blooms relatively early in the season with single or semi-double pink flowers
- ‘Mary Stoker’ – an early-season mum with apricot yellow, single-flower heads
- ‘Apricot Moneymaker’ – a midseason, anemone-style mum with bronze petals
- ‘Ruby Mound’ – an early-season bloom with large, maroon-red flowers
- ‘Patriot’ – a mid- to late-season bloomer with pure white pompom-shape flowers
- ‘Tripoli’ – a very late-season bloomer with daisy-like flowers of vibrant pink with yellow centers
Hardy Chrysanthemum Care
Perennial mums can be planted as soon as the soil warms in the spring. Pinch approximately one inch from the branch tips two to three times during the growing season to encourage branching and a sturdier plant. Early bloomers that bloom in mid-September should be pinched no later than mid-June. October bloomers can be pinched up until mid-July, with the rule of thumb being not to pinch any closer than three months to bloom time.
The plants should be fertilized regularly throughout the growing season. After the blooms fade in the fall, the plants can be cut down to about six inches and covered with dry mulch, such as straw. Plants can be lifted and divided every two to three years.
Mums planted in mixed borders provide late season color, especially when planted with other late-season bloomers such as sedum, Russian sage, asters and gaillardia. Mum foliage can also fill in and hide unattractive fading spring bloomers. Deer and rabbits tend to avoid plants with fragrant leaves and fuzzy texture, both of which are attributes of mums, making them fairly resistant.
Mums thrive in full sun but can handle a bit of shade. They can handle several soil types but do best in rich soil that has sharp drainage. Poor soil drainage will cause the plants to rot. They like a soil pH slightly on the acidic side. Mums require a lot of water. Give them one inch per week during the early growing season; and then increase watering to two or three times a week as the flower buds mature and the flowers begin to open.
Here are some tips to assure hardy mums will survive our cold winters: Give the roots and crown of the plant extra protection. Leave the foliage on the plants until spring. Do not prune them back after frost has turned them brown. After a frost, either mulch the plants heavily with at least 4 to 6 inches of mulch or pot them up and move the pots to a more protected spot in the garden for the winter. If you choose to move the plants, do so before the first hard freeze.
When you plant the mums in mid-May, after all danger of frost is past, include a time-released fertilizer (12-6-6). This will feed the plants for about three months and you may only have to fertilize them once. Mums need nitrogen and potassium before flower buds form to promote healthy roots, bud development, and a vigorous plant. Established plants should not be fed after July, so new growth is not injured by frost.
Propagating Hardy Chrysanthemums
You can propagate mums several ways: division, seeds and cuttings. The most straightforward and fastest method is through division. Divide plants that have grown in the garden for at least two years. Do this in the spring. Pick plants that are at least 6 inches tall. Be careful not to damage the roots. Replant at least 18 inches apart. Mums can grow from seeds, but since most are hybrids, the new plants may not be true to the parent. If you want to give it a try, start seeds indoors six to eight weeks before the last frost date and harden them off before transplanting outdoors.
Taking stem cuttings is an excellent way to assure your new plants will match the parent. Cut a stem at least four inches long, dip the cut end into a rooting hormone and plant it in a container. Wait about four weeks or so for a root to grow and for the plant to grow another two inches, then transplant it outside.
Planting in Containers
Be sure to plant your mums in a pot with drainage holes. Water the soil surface using a sprinkling can until water begins to drain from the bottom of the pot. Water should drain freely through the soil and out the bottom of the pot when watering. Soil should remain moist but not soggy. Soggy soil can cause root rot and other diseases.
If you purchase hardy mums in the fall already flowering in containers (and plan to leave them in containers), water them daily and fertilize them weekly with a diluted water-soluble fertilizer to prolong blooming. These mums have been coddled in nurseries and coaxed to set buds for September blooms. That means they are putting energy into blooming, not into growing roots. So transplanting these mums into the garden in late summer or early fall does not guarantee sufficient time for the plants to become established. In our sub-zero winters, perennial plants need strong roots to anchor them into the ground. Repeated freezing and thawing of the soil can heave the plant out of the ground and kill the roots. Your best bet to have them survive the winter would be to bury the pot in the soil in a protected area, mulch heavily and hope for new sprouts in the spring when they can be transplanted into the garden.
Plan to include some perennial mums in your gardens next spring. You may still want to purchase annual mums for fall color to complement pumpkins and flowering cabbages in your containers. But you can buy fewer and discard them at the end of the season, knowing that your perennial plants will provide late-blooming color in your gardens, year after year.
Article source: Garden Design Newsletter – August 20, 2021
Thespruce.com – How to Grow Hardy Chrysanthemum (Garden Mum) By Marie Iannotti – Updated on 02/23/21 https://www.thespruce.com/growing-hardy-mums-1402850
Photo credit: The Spruce/Gyscha Rendy
