Chrysanthemum in Zone 4A — Great Plains

Chrysanthemums bring a burst of color to your Plains garden just as the season starts to cool, providing a much-needed visual boost. They're great for cut flowers, adding a touch of beauty to your home as you prepare for winter. Plus, their late-season blooms offer nectar to pollinators when many other flowers are fading.

Our region's extreme weather can be a challenge, but with careful timing and a bit of planning, you can absolutely grow beautiful mums. Our growing season, though shorter at around 138 days, is still enough time for these beauties to thrive if you get them off to a good start.

Starting chrysanthemum seeds indoors in our climate gives you a head start, but it's not essential if you can find good starts in spring. If you want to try it, sow seeds indoors from early to late March, about eight weeks before you plan to transplant them.

Use seed trays with a good seed-starting mix. Keep them warm (around 70°F) and provide plenty of light, either from a sunny window or a grow light. Bottom watering is a great way to keep the soil moist without damping off the seedlings. Just set the tray in a shallow dish of water and let the soil soak it up. Be prepared for temperature swings in spring.

Transplant your chrysanthemum seedlings outdoors from early May through early June, after the last expected frost. Before planting, harden them off by gradually exposing them to outdoor conditions for about a week. This helps them adjust to our intense sunshine and variable temperatures.

Space plants 12-18 inches apart in a sunny spot with well-drained soil. Keep an eye on the weather forecast – we can still get late frosts or even hail in early May, so be ready to cover your plants if needed. Alternatively, buy potted mums in the fall, or starts in the spring.

Watering is crucial for chrysanthemums, especially in our Plains climate where we can swing from drought to periods of heavy rain. They need consistent moisture, but don't like to be waterlogged. During the hot summer months, aim to water deeply about once or twice a week, providing about an inch of water each time.

Stick your finger about two inches into the soil. If it feels dry, it's time to water. Water at the base of the plant to avoid wetting the foliage, which can encourage disease in our low-to-moderate humidity. Consistent moisture is especially important when buds are forming.

Watch for signs of underwatering, like wilting leaves, or overwatering, like yellowing leaves and soggy soil. A layer of mulch around the base of the plants can help retain moisture and regulate soil temperature, which is especially helpful during our extreme temperature swings.

Pruning chrysanthemums is key to getting those full, bushy plants loaded with flowers. Start pinching the growing tips every two to three weeks, beginning when the plants are about 6 inches tall. Pinch off the top set of leaves on each stem.

Continue this process through July 4th. This encourages side branching and more blooms. After July 4th, stop pinching to allow flower buds to develop for a beautiful fall display. You can remove any dead or damaged leaves throughout the season. As the first frost approaches in late September, you can cut back the plants to a few inches above the ground to prepare them for winter.

You can expect your first chrysanthemum blooms from mid-July through early September, depending on the variety and when you transplanted. Chrysanthemums are fall-blooming, so they'll really hit their stride as the weather cools down.

The flowers last for weeks in the garden, providing a long-lasting show of color. To harvest for bouquets, cut the stems when the flowers are fully open. Cut at an angle just above a leaf node. This encourages new growth.

Continue harvesting blooms throughout the fall to encourage more flowers. As the first frost approaches in late September, you can cut all the remaining flowers to enjoy indoors.

Chrysanthemums can encounter a few common problems, but with vigilance, you can keep your plants healthy. Here's what to watch out for:

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, winding trails within the leaves. *What causes it:* Larvae tunneling between leaf surfaces. *How to fix/prevent it:* Remove and destroy affected leaves. Use row covers to prevent adult flies from laying eggs. Insecticidal soap or neem oil can help.

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 summers, low-to-moderate humidity, and variable rainfall can create conditions favorable for spider mites and rust. Consistent monitoring and proactive measures are key to keeping your chrysanthemums healthy. Be especially diligent about watering during dry spells and providing good air circulation to prevent fungal diseases.

Chrysanthemums make great companions for several plants in your Plains garden. Plant them near tomatoes and peppers. Chrysanthemums can help repel aphids and other pests that commonly attack these vegetables.

Lettuce also benefits from being planted near chrysanthemums. The mums can provide some shade during the hottest part of the day, preventing the lettuce from bolting. Avoid planting chrysanthemums near because they can compete for nutrients and water.