Chrysanthemum in Zone 3B — Great Plains

Chrysanthemums bring a burst of color to your Great Plains garden as summer winds down. The vibrant blooms are perfect for late-season bouquets and add a cheerful touch when other plants are fading. Plus, they're relatively easy to grow here, offering a satisfying reward for your efforts.

Our region's extreme weather can be a challenge, but with a bit of planning, you can definitely enjoy chrysanthemums. Our 118-day growing season means starting seeds indoors or buying starts is essential to get those beautiful blooms before our first frost arrives around mid- September.

Starting chrysanthemum seeds indoors in our region can be a good way to get a jump on the season, especially in Zone 3B where our growing season is shorter. It's not essential, as you can always purchase starts in the spring, but if you want more variety, starting from seed is the way to go.

Start your seeds indoors from mid March through early April, giving them about 8 weeks to grow before transplanting. Use seed trays with a good seed-starting mix and keep them in a warm spot with plenty of light. Bottom watering is great to avoid damping off – just set the tray in a shallow dish of water and let the soil soak it up. Keep in mind that spring in the Plains can be unpredictable, so be prepared to adjust your plans if we get a late cold snap.

Transplant your chrysanthemum seedlings outdoors from mid May through mid June, after the risk of frost has passed. Before transplanting, harden off your seedlings by gradually exposing them to outdoor conditions for about a week. This helps them adjust to the sun and wind, which can be particularly intense in the Plains.

Space your plants 12-18 inches apart in a sunny spot with well-drained soil. Keep an eye on the weather forecast, as we sometimes get hail this time of year. If hail is predicted, cover your young plants with buckets or tarps to protect them. Buying potted mums in fall or starts in spring is always an option if you don't want to start from seed.

Chrysanthemums need consistent moisture, especially during bud formation, but they don't like to sit in soggy soil. In the Great Plains, where we often experience hot temperatures and variable rainfall, watering correctly is key. Aim to water deeply at the base of the plant, avoiding wetting the foliage, which can encourage fungal diseases in our low-to-moderate humidity.

During hot summer weeks, when temperatures reach into the 90s, you'll likely need to water your chrysanthemums about 1 inch of water per week. Use the "finger test" – stick your finger about 2 inches deep into the soil. If it feels dry, it's time to water. In periods of heavy rainfall, you may not need to water at all.

Signs of underwatering include wilting leaves and dry soil. Overwatering can cause yellowing leaves and root rot. Mulching around your plants with straw or wood chips can help retain moisture and regulate soil temperature, which is especially helpful in our extreme climate.

Pruning chrysanthemums is crucial for encouraging bushy growth and abundant blooms. The trick is to pinch off the growing tips every 2-3 weeks through July 4th. This encourages the plant to branch out and produce more flowers.

Pinch off just the top inch or so of the stem, leaving the rest of the plant intact. Stop pinching after July 4th, as this allows the plant to focus on developing flower buds for fall blooming. As the first frost approaches around mid- September, you can cut back the dead foliage to tidy up the plant.

You can expect your first chrysanthemum blooms from late July through mid September, depending on the variety and when you planted them. Chrysanthemums are fall-blooming plants, so they'll provide a beautiful display as your summer flowers fade. The flowers last for weeks in the garden.

Harvest the flowers for bouquets when they are fully open and the petals are firm. Cut the stems at an angle, just above a leaf node. This encourages new growth and continued production. Deadhead spent flowers regularly to keep the plant looking tidy and to encourage more blooms.

As the first frost approaches around mid- September, you can cut the remaining flowers to enjoy indoors. You can also try to overwinter your chrysanthemums by cutting them back and covering them with a thick layer of mulch, but success is not guaranteed in our harsh Plains climate.

Chrysanthemums, like all plants, can have their share of problems. Here are a few common issues you might encounter 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 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 or blotches within the leaves. Leaves may appear distorted or have a papery texture. *What causes it:* Larvae of small flies that burrow between the leaf surfaces to feed. More prevalent during warm, dry periods. *How to fix/prevent it:* Remove and destroy infested leaves. Insecticidal soap or neem oil can help control infestations. Floating row covers can 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: The hot heat and variable rainfall in the Great Plains can stress chrysanthemums, making them more susceptible to pests and diseases. Drought stress can lead to spider mite infestations, while periods of high humidity can encourage rust. Monitor your plants regularly and take action quickly to address any problems.

Chrysanthemums benefit from companion planting, and some plants work particularly well in the Great Plains. Tomatoes and peppers make good companions because they provide some shade during the hottest part of the day, protecting the chrysanthemums from scorching in our intense summer sun. Lettuce also works well, as it helps to keep the soil cool and moist.

Avoid planting chrysanthemums near plants that are susceptible to the same pests and diseases, such as asters. These plants can attract aphids and other problems that can spread to your chrysanthemums.