Chrysanthemum in Zone 6B — Great Plains

Chrysanthemums, or mums, aren't just the colorful showstoppers you see lining porches in the fall. They bring vibrant color to your garden, offer long-lasting cut flowers, and are surprisingly hardy for our Great Plains climate. Plus, their late-season blooms provide a welcome pop of color when other flowers are fading.

Sure, we deal with extreme temperature swings and the occasional bout of drought here on the Plains. But with a little planning and attention to timing, you can absolutely grow beautiful mums. Our 198-day growing season in Zone 6B gives you ample time to enjoy their blooms.

Starting mums indoors gives you a head start, but it's not always essential unless you're chasing a specific variety. If you want to try it, start seeds indoors from early to late February, about eight weeks before you plan to transplant them outside.

Use seed trays with a good seed-starting mix, and keep them warm (around 70°F) and under grow lights. Bottom watering helps prevent damping-off, a common problem with seedlings. Keep in mind our variable spring weather; even a head start indoors won't guarantee a smooth transition if we get a late freeze.

Transplant your mum seedlings outdoors from early April through early May, once the danger of hard frost has passed. Before planting, harden them off by gradually exposing them to outdoor conditions for about a week. This helps them adjust to the Plains wind and temperature swings.

Space your plants 12-18 inches apart in a sunny spot with well-drained soil. Keep an eye on the weather forecast; a late cold snap can still happen. Many gardeners in our region opt to buy established mums in the fall for instant color, or purchase starts in the spring to avoid the hassle of seed starting altogether.

Mums need consistent moisture, especially during bud formation. Aim to water deeply at the base of the plant, rather than overhead, to avoid fungal issues in our low-to-moderate humidity.

During the heat of the summer, you'll likely need to water two to three times a week, providing about an inch of water each time. The "finger test" is your friend: stick your finger about two inches into the soil. If it feels dry, it's time to water. In periods of variable rainfall, keep an eye on your plants and supplement as needed.

Signs of underwatering include wilting leaves and dry, crispy edges. Overwatering can lead to yellowing leaves and root rot. A layer of mulch around the base of the plants helps retain moisture and regulate soil temperature, which is especially helpful during our extreme temperature swings.

Pinching your mums is the key to getting a bushier plant with more blooms. Start pinching the growing tips every two to three weeks, beginning when the plants are about 6 inches tall.

Continue this process through July 4th. After that date, stop pinching to allow the flower buds to develop. As the season winds down and we approach our first frost around late October, you can leave the spent flowers on the plant or cut them back for a tidier appearance.

Expect your first mum blooms from mid-June through early August, depending on the variety and when you transplanted. Mums are known for their long-lasting flowers, both in the garden and in bouquets.

Harvest flowers for cutting when they are fully open. Use sharp, clean scissors or pruners to cut the stems at an angle. Removing spent flowers encourages the plant to produce more blooms. As late October approaches and the first frost threatens, cut any remaining blooms to enjoy indoors. The rest of the plant can be left in the garden and cut back after it dies down.

Here are some common problems to watch out for with mums in our region:

Aphids

• What it looks like: Clusters of tiny, soft-bodied insects (green, black, or white) on stems and leaf undersides. Sticky honeydew residue. Curled or distorted new growth.
• What causes it: Rapid-reproducing sap-sucking insects. Populations explode in warm weather. Ant colonies may farm them for honeydew.
• How to fix/prevent it: Strong water spray knocks them off. Encourage ladybugs and lacewings (natural predators). Insecticidal soap for heavy infestations. Neem oil works systemically. Avoid excess nitrogen fertilizer (it attracts them).

Spider Mites

• What it looks like: Fine stippling on leaves (tiny white dots). Fine webbing on leaf undersides and between stems. Leaves turn bronze or yellow.
• What causes it: Tiny arachnids that thrive in hot, dry conditions. Populations explode in drought stress.
• How to fix/prevent it: Strong water spray (daily for a week) is the best treatment. Increase humidity around plants. Neem oil or insecticidal soap. Release predatory mites (Phytoseiulus persimilis). Avoid broad-spectrum pesticides that kill predators.

Leaf Miners

• What it looks like: Tan or white winding trails inside the leaves. Leaves may appear blotchy or distorted.
• What causes it: Larvae of small flies that tunnel between the leaf surfaces to feed.
• How to fix/prevent it: Remove and destroy affected leaves. Insecticidal soap or neem oil can help control infestations. Use row covers to prevent adult flies from laying eggs on the plants.

Rust

• What it looks like: Rusty orange, yellow, or brown pustules on leaves and stems, mostly on undersides. Leaves yellow and drop prematurely.
• What causes it: Various rust fungi that spread via wind-borne spores. Favored by warm, humid conditions with moisture on leaves.
• How to fix/prevent it: Remove affected leaves. Avoid overhead watering. Improve air circulation. Apply sulfur or copper fungicide. Don't work among wet plants. Rotate crops.

Great Plains Specific Challenges: Our hot summer heat, combined with variable rainfall, can stress mums and make them more susceptible to pests and diseases. The wind can also damage plants, so providing some wind protection is essential. Regular watering and monitoring for problems will help keep your mums healthy and blooming.

Good companions for mums include tomatoes and peppers. Mums can help repel some pests that bother tomatoes and peppers, and in turn, these taller plants can provide some wind protection for the mums. Lettuce is another good companion; its low growth habit won't compete with the mums, and the mums can provide some shade during the hottest part of the day. Avoid planting mums near any plant that requires consistently wet soil. The drier conditions that mums prefer will cause problems for those other plants.