Chrysanthemum in Zone 8A — Desert Southwest

Chrysanthemums bring a burst of color to your Desert Southwest garden, especially during the late summer and fall when other blooms are fading. Their vibrant flowers add a touch of beauty to your landscape and make excellent cut flowers for indoor enjoyment. Plus, their late bloom time provides nectar for pollinators when many other sources have dried up in our extreme heat.

Desert gardening can be tough, and Chrysanthemums do need some attention to thrive here. But with careful timing, proper watering, and a little shade during the hottest part of the year, you can enjoy these beauties. Our long 265-day growing season gives you plenty of time to get them established for a stunning fall display.

Starting Chrysanthemum seeds indoors is an option, but honestly, most of us in the Desert Southwest find it easier to buy starts or established plants. If you're determined to start from seed, aim for early to late January – about 8 weeks before you plan to transplant outdoors.

Use seed trays with a good seed-starting mix. Keep the soil consistently moist by bottom watering – set the tray in a shallow dish of water until the surface of the soil is damp. You'll need supplemental light since our natural light is still weak at that time of year. Remember, spring comes very-early here, so keep an eye on the weather!

Transplant your Chrysanthemum seedlings outdoors from early March through early April. Before planting, harden them off by gradually exposing them to outdoor conditions for about a week. This prevents shock from our intense Desert Southwest sun.

Space plants 12-18 inches apart in well-draining soil. Even though it’s early spring, watch out for late cold snaps. Buying established plants from a local nursery in the spring or even potted mums in the fall is often the easiest route for Desert Southwest gardeners.

Consistent watering is key for Chrysanthemums, especially in our arid Desert Southwest climate. While they aren't drought-tolerant, avoid overwatering, which can lead to root rot. The goal is consistent moisture, not soggy soil.

During the spring and fall growing seasons, aim to water deeply about 2-3 times per week, providing about 1 inch of water each time. Stick your finger about 2 inches into the soil – if it feels dry, it's time to water. During the monsoon season, adjust your watering schedule based on rainfall, but don't rely on monsoon moisture alone. In the extreme heat of summer, you may need to water daily, especially for plants in pots.

Always water at the base of the plant to avoid wetting the foliage, which can encourage fungal diseases in our climate. Signs of underwatering include wilting leaves and dry, brittle stems. Overwatering can lead to yellowing leaves and mushy stems. A layer of organic mulch, like composted leaves, helps retain moisture and regulate soil temperature.

Pruning Chrysanthemums is essential for encouraging bushier growth and more blooms. The key is pinching – removing the growing tips of the stems.

Start pinching when the plants are about 6 inches tall and continue every 2-3 weeks until July 4th. This encourages side shoots to develop, resulting in a fuller plant with more flowering stems. Stop pinching after July 4th to allow flower buds to form for fall blooming. As the first frost approaches in late November, you can cut back the plants to a few inches above the ground.

You can expect your first Chrysanthemum blooms from mid-May through early July, depending on the variety and when you planted them. Chrysanthemums are fall-blooming. Their flowers last for weeks in the garden, providing long-lasting color.

Harvest the flowers when they are fully open, cutting the stems at an angle. This encourages the plant to produce more blooms. Remove any leaves below the water line to prevent bacterial growth in your vase. To encourage continued blooming, deadhead spent flowers regularly. As the first frost approaches in late November, you can cut the remaining flowers to enjoy indoors.

Here are some common problems you might encounter with Chrysanthemums in the Desert Southwest:

Aphids *What it looks like:* Clusters of tiny green, black, or white insects on stems and leaf undersides. Sticky honeydew and curled or distorted new growth. *What causes it:* These sap-sucking insects thrive in warm weather and can rapidly reproduce. Ants often protect them. *How to fix/prevent it:* Strong water spray to knock them off. Encourage ladybugs and lacewings. Use insecticidal soap or neem oil. Avoid excessive nitrogen fertilizer.

Spider Mites *What it looks like:* Fine stippling on leaves (tiny white dots), webbing on leaf undersides, and leaves turning bronze or yellow. *What causes it:* These tiny arachnids thrive in hot, dry conditions, which we have plenty of in the Desert Southwest. Drought stress exacerbates the problem. *How to fix/prevent it:* Strong water spray daily for a week. Increase humidity around plants. Use neem oil or insecticidal soap. Release predatory mites.

Leaf Miners *What it looks like:* *What causes it:* *How to fix/prevent it:*

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:* Rust fungi spread by wind-borne spores and thrive in warm, humid conditions. Even though our humidity is low, monsoon moisture can create localized humid pockets. *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.

Desert Southwest Specific Challenges: The extreme heat and low humidity of our region can stress Chrysanthemums, making them more susceptible to pests and diseases. Sunscald can also be an issue, especially for plants in full afternoon sun. While monsoon rainfall can provide some relief, it can also create conditions favorable for fungal diseases. Consistent monitoring and proactive measures are key to success.

Good companions for Chrysanthemums in the Desert Southwest include tomatoes and peppers. Tomatoes offer some shade during the hottest part of the day, helping to prevent sunscald. Peppers benefit from the pest-repelling properties of Chrysanthemums. Lettuce planted nearby can also benefit from the partial shade offered by Chrysanthemums, extending its growing season.

Avoid planting Chrysanthemums near plants that require very different watering schedules, as this can lead to over or underwatering issues. Also, avoid planting them near aggressive spreaders that might compete for resources in our often-poor Desert Southwest soils.