Chrysanthemum in Zone 9B — Gulf Coast

Chrysanthemums, or mums, are a fantastic way to add late-season color to your Gulf Coast garden. The vibrant blooms bring cheerfulness as other flowers fade, and they make beautiful cut flowers to brighten your home. Plus, they're relatively easy to grow, rewarding you with a burst of color just when you need it.

Our long growing season here on the Gulf Coast means you can enjoy mums for an extended period. While the high humidity and occasional hurricane can present challenges, careful planning and attention to watering can ensure a successful and beautiful display. You've got a 319-day window to work with, so let's make the most of it.

Starting chrysanthemum seeds indoors in our climate isn't always necessary, given our mild winters and long growing season. However, if you're after specific varieties or want a head start, it's certainly doable.

If you choose to start indoors, aim for late November through mid December. Use seed trays with a good seed-starting mix and provide warmth and light – a simple grow light works wonders. Remember to water from the bottom to avoid damping off, which can be a problem with our high humidity. This also helps develop strong roots.

Transplanting is the most common and reliable way to grow mums in the Gulf Coast. You can find potted mums at local nurseries in the fall, or start with seedlings in the spring.

If you're using seedlings, transplant them outdoors in late January through late February. Before transplanting, harden them off by gradually exposing them to outdoor conditions for about a week. Space them 12-18 inches apart in a sunny spot. Keep an eye on the weather; we can still get some cool snaps during this time, so protect them if needed.

Watering is absolutely critical for healthy mums in our humid Gulf Coast climate. While they need consistent moisture, especially during bud formation, overwatering can lead to fungal problems.

During the warmer months, especially when we aren't getting our usual afternoon storms, check the soil moisture by sticking your finger about 2 inches deep. If it feels dry, it's time to water. Aim for about 1 inch of water per week, delivered at the base of the plant to avoid wetting the foliage. Overhead watering can encourage fungal diseases due to our high humidity.

Signs of underwatering include wilting leaves and dry soil. Overwatering can manifest as yellowing leaves and potentially root rot. Mulching around your mums with pine straw or shredded leaves helps retain moisture and suppress weeds, but avoid piling mulch directly against the stems.

Pruning is essential to encourage bushy growth and abundant blooms on your chrysanthemums. The key is to pinch the growing tips regularly.

Pinch off the top inch or so of the stems every 2-3 weeks, starting when the plants are about 6 inches tall and continuing through July 4th. This encourages side shoots and more flowers. Be sure to actually pinch or cut the tips off with clean pruners. After July 4th, stop pinching to allow the flower buds to form. As the first frost approaches in mid- December, you can cut back the plants to a few inches above the ground.

Your chrysanthemum harvest will typically begin in early April and continue through late May, depending on the variety and when you transplanted. These are fall-blooming so the listed time isn't accurate.

The best time to harvest is when the flowers are fully open and the colors are vibrant. Use sharp, clean scissors or pruners to cut the stems, leaving a few inches of stem on the plant to encourage further blooming. They don't ripen off the vine, so be sure they are perfect before cutting them!

Deadheading spent flowers regularly will encourage continuous blooming throughout the season. As the first frost approaches in mid- December, you can cut the remaining flowers for indoor enjoyment.

Chrysanthemums can face a few common problems in our Gulf Coast gardens, but with a little vigilance, you can keep them healthy.

• 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, squiggly lines or blotches inside the leaves. Leaves may appear distorted or have brown spots.
• What causes it: Larvae of small flies that tunnel between the leaf surfaces, feeding on the leaf tissue.
• How to fix/prevent it: Remove and destroy infested leaves. Encourage beneficial insects like parasitic wasps. Cover plants with row covers to prevent adult flies from laying eggs. Use neem oil preventatively.
• 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.

Gulf Coast Specific Challenges: The hot heat, very-high humidity, and wet-year-round rainfall in our region create the perfect environment for fungal diseases like rust. Good air circulation, avoiding overhead watering, and promptly removing affected foliage are crucial for keeping your mums healthy.

Chrysanthemums benefit from companions that deter pests or improve soil conditions. Tomatoes and peppers make good companions because they help deter aphids and other pests that can affect mums.

Lettuce can also be a beneficial companion, as it provides ground cover that helps retain moisture and suppress weeds. Avoid planting mums near plants that are susceptible to the same diseases, such as other members of the Aster family.