Chrysanthemum in Zone 5A — Great Plains

Chrysanthemums, or mums, bring a vibrant burst of color to your Great Plains garden just as the days start to shorten. Their late-season blooms provide a welcome contrast to the fading landscape and make beautiful cut flowers to brighten up your home. Plus, their relatively compact growth habit means you can tuck them into existing beds or containers.

Growing mums here isn't without its challenges. We have to contend with extreme temperature swings and the risk of hail. But with a little planning and attention to timing within our roughly 168-day growing season, you can enjoy these beauties in your garden.

Starting Chrysanthemum seeds indoors isn't essential, especially since you can often find healthy starts at local nurseries in spring. However, if you're looking for specific varieties or want a head start, sow seeds indoors from late February through mid March, about 8 weeks before you plan to transplant them.

Use seed trays with a good seed-starting mix. Keep the soil consistently moist, and provide warmth with a heat mat. Bottom watering is a great trick – set the tray in a shallow dish of water and let the soil soak it up from the bottom. Our variable spring weather means you'll need to monitor them closely indoors until transplant time.

Transplant your Chrysanthemums outdoors from late April through late May, once the risk of hard frost has passed. Before planting, harden off your seedlings by gradually exposing them to outdoor conditions for about a week. This helps them adjust to the sun and wind.

Space plants 12-18 inches apart in well-draining soil and a spot that gets at least 6 hours of sun. Given our Plains winds, consider a location with some natural wind protection. You can also buy established potted mums in fall or starts in spring from local nurseries.

Chrysanthemums need consistent moisture, especially during our hot Plains summers. Aim for about 1 inch of water per week, either from rainfall or irrigation. Stick your finger about 2 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 fungal diseases in our low-to-moderate humidity. Overwatering can lead to root rot, indicated by yellowing leaves and wilting. Underwatering results in dry, crispy leaves and stunted growth.

A layer of mulch around the base of your plants can help retain moisture and regulate soil temperature, which is especially helpful during our extreme temperature swings.

To encourage bushier plants with more blooms, pinch off the growing tips of your Chrysanthemums every 2-3 weeks through July 4th. This forces the plant to branch out. Be sure to pinch off just the very tip of the stem, leaving the rest of the foliage intact.

After July 4th, stop pinching to allow flower buds to form. As the first frost approaches in early October, you can cut back the plants to a few inches above the ground.

You can expect your first Chrysanthemum blooms from early July through late August, depending on the variety and when you planted. The flowers last for weeks in the garden, providing a long season of color.

Harvest blooms for bouquets when the flowers are fully open and the colors are vibrant. Cut the stems at an angle, leaving several leaves on the plant to encourage further blooming.

As the first frost approaches in early October, you can cut the remaining flowers to enjoy indoors. While mums aren't hardy perennials in all parts of Zone 5A, they can sometimes overwinter with heavy mulching, especially if planted in a protected location.

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 in drought stress. Our hot, dry summers provide ideal conditions for spider mites.
• 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 inside the leaves. Leaves may look blotchy or distorted.
• What causes it: Larvae of small flies that burrow between the leaf surfaces to feed.
• How to fix/prevent it: Remove and destroy affected leaves. Cover plants with row covers to prevent flies from laying eggs. Insecticidal soap or neem oil can help control infestations.

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 combination of hot heat and variable rainfall in the Great Plains can stress Chrysanthemums, making them more susceptible to pests and diseases. Consistent watering and good air circulation are essential for healthy plants. Wind protection also minimizes leaf damage that can invite disease.

Chrysanthemums benefit from companions that offer shade or deter pests. Tomatoes and peppers make good neighbors, as their larger size can provide some afternoon shade during our intense summer heat. Lettuce planted nearby can act as a ground cover, helping to retain moisture.

Avoid planting Chrysanthemums near plants that are prone to fungal diseases, as this can increase the risk of rust.