Chrysanthemum in Zone 5B — Great Plains

Chrysanthemums are a classic choice for adding late-season color to your Great Plains garden. Their bright, cheerful blooms provide a welcome burst of beauty as other flowers fade, and they make excellent cut flowers to bring inside and brighten up your home. Plus, they're surprisingly hardy and can handle the temperature swings we often see in our neck of the woods.

Growing Chrysanthemums in our Zone 5B climate definitely has its challenges, with the risk of hail and those extreme temperature swings. But with a little planning and attention to timing, you can enjoy a stunning display of blooms before our 178-day growing season comes to an end.

Starting Chrysanthemums indoors isn't strictly necessary, but it can give you a head start, especially if you're aiming for an earlier bloom. If you want to go this route, aim to start your seeds indoors from mid February through early March, about 8 weeks before you plan to transplant them outside.

Use seed trays with a good seed-starting mix, and keep them in a warm location with plenty of light. Bottom watering is your friend here – it helps prevent damping off and encourages strong root growth. Keep in mind that our spring weather can be so variable, so be prepared to adjust your transplant schedule if we get a late cold snap.

Transplanting Chrysanthemums outdoors should happen from mid April through mid May, once the risk of a hard frost has passed. Before planting, harden off your seedlings by gradually exposing them to outdoor conditions for about a week.

Space the plants 12-18 inches apart in a sunny spot with well-draining soil. Keep an eye on the forecast – those late spring temperature swings can be brutal, so protect your transplants if a cold snap is coming. Many gardeners here in the Plains opt to buy potted mums in the fall or starts in the spring to skip the seed-starting process altogether.

Chrysanthemums need consistent moisture, but they don't like to be waterlogged. During the heat of summer, especially when temperatures hit those typical highs around 93°F, you'll likely need to water them deeply every few days. The finger test is a good way to check: if the top 2 inches of soil are dry, it's time to water.

Aim for about 1 inch of water per week, either through rainfall or irrigation. Water at the base of the plant to avoid wetting the foliage, which can lead to fungal diseases, especially with our low-to-moderate humidity.

Keep an eye out for signs of underwatering, like wilting leaves, or overwatering, like yellowing leaves. A layer of mulch around the base of the plants can help retain moisture and regulate soil temperature, which is especially helpful given our variable rainfall.

Pinching your Chrysanthemums is key to getting a full, bushy plant with lots of flowers. Start pinching the growing tips every 2-3 weeks, beginning when the plants are about 6 inches tall. You'll want to continue pinching until around July 4th.

Pinch off the top set of leaves on each stem, which encourages the plant to branch out. After July 4th, stop pinching – this allows the flower buds to develop for fall blooming. As the first frost approaches around mid- October, you can cut back the plants to a few inches above the ground.

You can expect your first Chrysanthemum harvest from late June through mid August, depending on when you planted and the specific variety. Fall-blooming mums will naturally be ready much later. The flowers last for weeks in the garden, so you'll have plenty of time to enjoy them.

Cut the flowers for bouquets when they are fully open, using a clean, sharp knife or scissors. Cut the stems at an angle, and remove any leaves that will be below the waterline in your vase. To encourage continued production, deadhead spent flowers regularly. As the first frost approaches in mid- October, you can harvest any remaining blooms to enjoy indoors.

Here are some common problems you might encounter with Chrysanthemums in the Great Plains:

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 during periods of 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 squiggly lines or blotches in leaves. Larvae visible inside the mines if you hold the leaf up to the light.
• What causes it: Larvae of small flies, moths, sawflies, or beetles that tunnel inside the leaf tissue.
• How to fix/prevent it: Remove and destroy affected leaves. Cover plants with row covers to prevent adult insects from laying eggs. Beneficial nematodes can help control soil-dwelling larvae. Insecticidal soap or neem oil can be effective against young larvae.

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: The hot, dry summers and variable rainfall in the Great Plains can stress Chrysanthemums, making them more susceptible to spider mites and other pests. Wind protection is also essential to prevent damage to the plants and flowers. Regular watering and monitoring for pests and diseases are crucial for success.

Chrysanthemums make good companions for several plants in your Great Plains garden. Tomatoes and peppers benefit from having Chrysanthemums nearby because the mums act as a natural insect repellent, deterring pests like aphids that can attack these vegetables. Lettuce also appreciates the shade that Chrysanthemums can provide during the hottest part of the summer, preventing bolting.

Avoid planting Chrysanthemums near members of the cabbage family, like broccoli and cauliflower. These plants can attract similar pests, like cabbage worms, which can then spread to your Chrysanthemums.