Chrysanthemum in Zone 7B — Mid-Atlantic

Chrysanthemums bring a burst of color to your Mid-Atlantic garden as other blooms start to fade, making them a welcome sight in our four-season climate. They're great for cut flowers, adding beauty to your home, and their late-season blooms perfectly complement the changing foliage. Plus, they're relatively easy to grow here.

Our humid summers and occasional deer pressure can present challenges, but with proper timing and care, you can enjoy a vibrant display of Chrysanthemums. Our 214-day growing season gives you plenty of time to get them established and blooming before the first frost.

Starting Chrysanthemums indoors is an option, especially if you want a head start on the season or specific varieties. Begin in late January through mid February, about eight weeks before you plan to transplant. Use seed trays with a good seed-starting mix, ensuring they have drainage.

Keep the trays warm and provide plenty of light, either with a grow light or a sunny window. Bottom watering helps prevent damping-off, a common issue with seedlings. Given our moderate spring, you can also buy starts from a local nursery when the weather warms up.

Transplant your Chrysanthemum seedlings outdoors in early to late April, once the danger of frost has passed. Before planting, harden them off by gradually exposing them to outdoor conditions for about a week. This acclimates them to the sun and wind, preventing shock.

Space the plants 12-18 inches apart in a sunny spot with well-draining soil. Keep an eye on the weather forecast during this time – we sometimes get unexpected cold snaps in April, so be prepared to cover your new transplants if necessary. You can also buy potted mums in the fall, or starts in spring, from local nurseries.

Chrysanthemums need consistent moisture, especially during our humid summers, but they don't like to sit in soggy soil. Aim for moderate watering, keeping the soil consistently moist but not waterlogged. Stick your finger about two inches deep into the soil; if it feels dry, it's time to water.

Typically, an inch of water per week is sufficient, but adjust based on rainfall. Water at the base of the plant to avoid wetting the foliage, which can encourage fungal diseases in our humid climate. Overwatering can lead to root rot, while underwatering will cause the leaves to wilt and the plant to stress.

Mulching around the base of the plants with straw or wood chips can help retain moisture and regulate soil temperature, especially during the hotter months. Keep an eye on the leaves, as yellowing can indicate overwatering, while crispy edges suggest underwatering.

Pinching your Chrysanthemums throughout the growing season encourages bushier growth and more abundant blooms. Begin pinching the growing tips every 2-3 weeks, starting when the plants are about 6 inches tall. This directs the plant's energy into producing more stems and, ultimately, more flowers.

Stop pinching around July 4th. This gives the plants enough time to set their flower buds for fall blooming. As the growing season winds down and the first frost approaches in early November, you can cut back the plants to a few inches above the ground to prepare them for winter dormancy.

Your Chrysanthemums will start blooming in early June through late July, depending on the variety and when you transplanted them. The flowers last for weeks in the garden, providing a long-lasting display of color. Cut the flowers for bouquets when they are fully open, choosing stems with strong, straight growth.

To harvest, use sharp, clean scissors or pruners to cut the stem at an angle, just above a leaf node. Removing spent flowers, or deadheading, encourages the plant to produce more blooms throughout the season. As the first frost approaches in early November, you can harvest any remaining blooms to enjoy indoors.

If you want to try to overwinter your mums, leave a few inches of stem on the plant after cutting the last flowers. Mulch heavily around the base to protect the roots from the cold.

Here are some common issues you might encounter with Chrysanthemums in the Mid-Atlantic:

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 leaves.
• What causes it: Larvae of small flies that tunnel between leaf surfaces.
• How to fix/prevent it: Remove and destroy affected leaves. Floating row covers prevent adult flies from laying eggs. Neem oil suffocates larvae inside mines. Spinosad insecticide targets larvae.

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.

Mid-Atlantic Specific Challenges: The combination of moderate-to-hot heat and humid humidity in the Mid-Atlantic creates an ideal environment for fungal diseases like rust and increases the likelihood of pest infestations. Monitor your plants regularly, provide good air circulation, and water at the base to minimize these issues.

Good companion plants for Chrysanthemums include tomatoes and peppers. Tomatoes help deter pests like aphids that can bother your mums. Peppers also offer some pest protection and don't compete heavily for resources. Lettuce is another good choice as it provides ground cover, helping to retain moisture in the soil, which benefits Chrysanthemums, especially during our humid summers.

Avoid planting Chrysanthemums near plants that are highly susceptible to fungal diseases, as this can increase the risk of spreading these problems to your mums. Also, avoid planting near aggressive spreaders that will compete for resources.