Chrysanthemum in Zone 9B — Desert Southwest

Chrysanthemums bring a burst of color to your Desert Southwest garden, especially when other blooms are fading. Their vibrant flowers make excellent cut arrangements, adding beauty indoors and out, plus they are relatively easy to grow here given our two growing seasons.

Desert gardening has its challenges, no doubt, but Chrysanthemums are manageable if you time things right. By starting early, you can enjoy these beauties during our long fall season, taking advantage of our 313-day growing season before the first frost arrives.

Starting Chrysanthemums indoors gives you a head start, especially since our spring warmth can arrive quickly. Sow seeds indoors from early to late December, about eight weeks before you plan to transplant.

Use seed trays with a good seed-starting mix, keep them warm (around 70°F), and provide plenty of light. Bottom watering is a great trick: set the tray in a shallow dish of water until the soil surface looks moist. Because spring comes early here, this method allows you to get a jump on the season.

Transplant your Chrysanthemum seedlings outdoors from early February through early March. Before transplanting, harden them off. Give them gradual outdoor exposure for about a week.

Space plants 12-18 inches apart in well-draining soil. You can also buy potted mums in the fall for immediate color, or starts in spring from local nurseries to make things easier.

Chrysanthemums need consistent moisture, especially here in the Desert Southwest. Water deeply at the base of the plant, aiming for about 1 inch of water per week, depending on rainfall. During our extreme heat, you might need to increase watering frequency.

Stick your finger about 2 inches into the soil to check moisture levels. If it feels dry, it's time to water. Avoid overhead watering to prevent fungal diseases, a good idea in our arid climate.

Overwatering signs include yellowing leaves and root rot, while underwatering shows up as wilting and crispy edges. Mulching around your plants with compost or shredded bark helps retain moisture and keeps the soil cooler during the hot months.

Pinching is key for bushy, floriferous Chrysanthemums. From the time your plant is a few inches tall until July 4th, pinch off the growing tips every 2-3 weeks. This encourages side shoots and more flower buds.

After July 4th, stop pinching to allow the flower buds to develop. In late fall, after the first frost around mid- December, cut back the dead foliage to the ground.

You can expect your first Chrysanthemum blooms from mid April through early June. The flowers last for weeks in the garden and make excellent cut flowers.

Harvest when the flowers are fully open. Cut the stems at an angle, leaving a few inches of stem on the plant. Regular harvesting encourages more blooms. As the first frost approaches in mid- December, cut any remaining flowers to enjoy indoors.

Chrysanthemums in the Desert Southwest can face a few common problems:

Aphids

• What it looks like: Clusters of tiny green, black, or white insects on stems and leaf undersides. Sticky honeydew residue and curled or distorted new growth.
• What causes it: Rapid-reproducing sap-sucking insects thrive in our warm climate. Ant colonies often farm them for honeydew.
• How to fix/prevent it: A strong spray of water knocks them off. Encourage ladybugs and lacewings. Use insecticidal soap for heavy infestations or neem oil. Avoid excess nitrogen fertilizer.

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: These tiny arachnids thrive in hot, dry conditions. Populations explode during periods of drought stress, common in our arid climate.
• How to fix/prevent it: A strong water spray (daily for a week) is the best treatment. Increase humidity around plants. Neem oil or insecticidal soap can help.

Leaf Miners

• What it looks like: White or tan squiggly lines or blotches on leaves. The larvae tunnel between leaf surfaces.
• What causes it: Tiny fly larvae that feed inside the leaves. They are more active in warmer months.
• How to fix/prevent it: Remove and destroy affected leaves. Use floating row covers to prevent adult flies from laying eggs. Spinosad sprays can be effective.

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, especially during monsoon season.
• 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.

Desert Southwest Specific Challenges: Our extreme heat and low humidity can stress Chrysanthemums, making them more susceptible to pests and diseases. The monsoon season can bring periods of high humidity that favor fungal diseases like rust. Consistent monitoring and proactive measures are key to healthy plants.

Good companions for Chrysanthemums in the Desert Southwest include tomatoes and peppers. They benefit from the pest-repelling properties of Chrysanthemums. Lettuce also works well, as it can provide ground cover and help retain moisture in our dry climate, offering a cooler root zone.

Avoid planting Chrysanthemums near because