COLUMBIA, Mo. – Autumn flowers are nature’s last brazen splash of the paintbrush before the sullen grays of winter come.
As summer’s annual flower gardens fade, Missouri gardeners need not dismay, says David Trinklein, associate professor of plant sciences at the University of Missouri and MU Extension horticulture specialist.
Bushel-basket sized mums, neon-bright asters and delicately fragranced pansies complement emerging fall foliage, undaunted by disappointing gardens from this summer’s drought, Trinklein says.
Mums are the anchors of fall gardens
Chrysanthemums are the hallmark of fall’s arrival and this season’s mums are big and beautiful. Trinklein recommends that mum lovers buy plants with healthy green leaves, good roots and partially opened buds rather than flowers in full bloom.
While most mums will be left in their original containers and used for fall decorations, gardeners can enjoy their beauty again next year by following a few simple guidelines. First, remove the plant carefully from its container and plant the mum in loose, well-drained soil. Water immediately and regularly to help the mum develop its root structure for next year.
After the first hard freeze, cut the plant back and mulch the plant to protect the crown. The mum will begin growth next year from the crown of the plant. In the spring, “pinch back” the growing points of the plant on about a bimonthly schedule from late May to no later than July 4. “You’re pinching away plant material you have worked hard to produce,” Trinklein says, but mums must be pinched early in the season to maximize fullness and the trademark dome appearance.
Trinklein also warns gardeners not to fertilize mums in the fall. “Feeding them now is the worst thing you can do, since it makes the plant more vulnerable to cold-weather damage,” he says. “Wait until spring.”
Brilliant asters complement mums
Asters with their petite daisylike blooms are one of fall’s most underappreciated plants, but they make a perfect accompaniment to the mum, which shares many of the same characteristics.
Unmatched in fall brilliance, asters are slightly more difficult to grow in this area, but they are worth the extra effort, Trinklein says. Asters enjoy a full-sun exposure in a well-drained soil of average fertility. Adding well-decomposed organic matter can help loosen tight soils. Garden asters purchased in bloom growing in containers need only be watered. Those established in a perennial garden should be given only modest amounts of fertilizer during the growing season since excess fertility leads to tall, “floppy” plants.
This summer’s drought helped discourage the development of powdery mildew, a troublesome disease for asters. Several new cultivars have been developed that are more tolerant of mildew than some of the older, more familiar ones.
Unlike chrysanthemums, asters have a fairly upright growth habit and range in height from 3 to 5 feet in nature. Although plant breeders have succeeded in developing shorter cultivars, most aster cultivars that have been overwintered as established plants in the garden need to be pinched back as they grow in order to keep them compact and attractive. After emerging in the spring and achieving a height of about 6 to 8 inches, plants should be pinched every two to three weeks until about July 25, the date on which flowering is triggered in most cultivars. Pinching results in a fuller plant with a more attractive floral display.
Pansies provide beauty, fragrance in fall
One of the most overlooked beauties of fall is the ornate pansy that provides both fall and early spring color. Older varieties of the plant are not as heat-tolerant as newer varieties, so newer versions will provide a longer, more glorious display of color. Most gardeners choose pansies that have been started by commercial greenhouses and are sold in bedding plant “packs.” Choose plants that are “stocky” with healthy leaves and free from pests. Plants with several unopened buds are preferable and likely will result in a spectacular display of color sooner.
Pansies enjoy cool temperatures and abundant sunshine. Unfortunately for pansy lovers, this combination of conditions is available only in the spring and fall in the Midwest. To extend the useful life of pansy in the spring or to get an earlier start on fall color, an exposure of morning sun followed by afternoon shade can be chosen. Although pansies should be considered an annual in Missouri, fall-planted pansies frequently survive winter and produce color in the late winter or very early spring after temperatures begin to warm.
Given the very fine and delicate nature of the root system of pansies, the soil in which they are planted should be porous and highly enriched with organic matter. The latter promotes good soil aeration, along with adequate water retention. Incorporating 3-4 inches of well-decomposed organic matter is a “best management practice” for preparing most soils for the production of annual flowers, including pansies, Trinklein says. Additional preplant fertilizer may or may not be required, depending upon the inherent fertility of the soil.
When planting, space pansies about 6 to 10 inches apart and water well, directing the water to the base of the plant. Pansies should never be allowed to dry and, in most settings, need 1-2 inches of water weekly. Additional fertilizer can be supplied in water-soluble form, if required.
Do fall cleanup and plant bulbs now
Trinklein said fall is the time for gardeners to plan for beautiful spring gardens. Gardeners should do cleanup now as the first defense against diseases next growing season and to improve aesthetics. He warns gardeners not to put garden waste in compost piles, to avoid the spread of diseases.
Now is also the time to plant spring-flowering bulbs. Dutch bulbs perform best when planted by mid-October. This gives them time to establish a good root system and also allows for the approximately 12 weeks of chilling they require, he said. Narcissus, which includes daffodil, is the only bulb that naturalizes well in Missouri, and Trinklein recommends them for hardiness and dependable spring beauty. Narcissus contains a toxic compound, especially in the bulb, that makes it unattractive as a food source to animals, unlike other traditional spring favorites.
For greatest effect in the landscape, plant bulbs in groups, not lined out in a row. Groupings of 10 or 12 are quite common, but for the best display of color, a scattering of 50 or more bulbs is needed. The latter sometimes is referred to as planting in “drifts.” The bulbs should be planted fairly densely in these groupings and spaced about 3 inches apart. Depth of planting varies with species but, as a rule, minor bulbs should be planted about three times their height in depth.
Like most plants that produce a bulb or bulblike storage structure, the minor bulbs require a loose, well-drained soil for good growth and performance. Incorporating organic matter into the area to be planted will help improve poorly drained soils. Alternatively, if soil is heavy, bulbs may be planted in a rock garden or on raised mounds to facilitate drainage.
A little fall work in the next few weeks will result in many hours of spring enjoyment, Trinklein said.