Chrysanthemum in Zone 5B — Mid-Atlantic

Chrysanthemums aren't just a pretty face; they bring a burst of late-season color to our Mid-Atlantic gardens when many other flowers are fading. Their vibrant blooms are perfect for fall bouquets, adding a cheerful touch as the days get shorter. Plus, they're surprisingly easy to grow here, offering a rewarding gardening experience.

While we face our share of challenges – think humid summers and the occasional deer browsing – with a bit of planning and attention to timing, you can successfully grow beautiful mums. Our 178-day growing season gives you plenty of time to nurture these beauties from spring to fall.

Starting chrysanthemums from seed indoors isn't the most common approach, but it gives you a head start, especially if you're after a specific variety that's hard to find as a transplant. Begin in mid February through early March, about eight weeks before you plan to move them outside.

Use seed trays with a good seed-starting mix and keep them in a warm spot (around 70°F) with plenty of light – a sunny windowsill or grow lights work well. Water from the bottom to keep the seedlings consistently moist without soaking the leaves. Remember, our spring weather in the Mid-Atlantic can be variable, so starting indoors offers protection from any unexpected late frosts.

The easiest way to grow chrysanthemums here in the Mid-Atlantic is by buying potted mums in the fall or starts in the spring. If you started seeds indoors, transplant them outdoors mid April through mid May, after the danger of frost has passed.

Before planting, harden off your seedlings by gradually exposing them to outdoor conditions for about a week. Choose a sunny spot with well-drained soil, spacing plants 12-18 inches apart. Keep an eye on the weather forecast; unexpected cold snaps can still happen this time of year.

Chrysanthemums need consistent moisture, especially during our moderate-to-hot, humid summers. Aim to water deeply at the base of the plant, providing about an inch of water per week, either from rainfall or your hose. Stick your finger about two inches into the soil – if it feels dry, it's time to water.

Avoid overhead watering as much as possible, especially in our humid climate, to prevent fungal diseases. Signs of underwatering include wilting leaves, while yellowing leaves could indicate overwatering. A layer of mulch around the base of the plants helps retain moisture and keeps the soil cool.

In the Mid-Atlantic, we often get even rainfall, but there will be stretches where you'll need to supplement. Pay attention to the forecast and adjust your watering schedule accordingly.

To encourage bushy plants with lots of flowers, pinch the growing tips of your chrysanthemums every 2-3 weeks until around July 4th. This simple step directs the plant's energy into producing more side shoots, which means more blooms later on.

Pinch off the tips of the stems, leaving the foliage below intact. After July 4th, stop pinching to allow the flower buds to form. As the first frost approaches around mid- October, you can cut back the plants to ground level.

Chrysanthemums grown in the Mid-Atlantic typically start blooming in late June through mid August, depending on the variety and when you transplanted them. You'll know they're ready to harvest when the flowers are fully open and the petals are firm.

Cut the stems at an angle, just above a leaf node, to encourage new growth. Harvesting flowers regularly will encourage the plant to produce more blooms throughout the season. As the first frost approaches, cut any remaining blooms to enjoy indoors.

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

Aphids

• What it looks like: Clusters of tiny green, black, or white insects on stems and undersides of leaves. You might also see a sticky honeydew residue and curled or distorted new growth.
• What causes it: These sap-sucking insects reproduce quickly, especially in warm weather. Ants often protect them to harvest the honeydew.
• How to fix/prevent it: A strong spray of water can knock them off. Encourage natural predators like ladybugs. Insecticidal soap or neem oil are effective for heavy infestations. Avoid over-fertilizing with nitrogen.

Spider Mites

• What it looks like: Fine stippling (tiny white dots) on leaves, fine webbing on leaf undersides and between stems. Leaves may turn bronze or yellow.
• What causes it: These tiny arachnids thrive in hot, dry conditions. Drought stress can worsen infestations.
• How to fix/prevent it: A strong spray of water daily for a week can help. Increase humidity around the plants. Use neem oil or insecticidal soap. Consider releasing predatory mites. Avoid broad-spectrum pesticides.

Leaf Miners

• What it looks like: Noticeable tan or white winding trails or blotches in the leaves.
• What causes it: These are the larvae of small flies, moths, sawflies, or beetles that burrow between the upper and lower leaf surfaces as they feed, leaving unsightly tunnels.
• How to fix/prevent it: Remove and destroy infested leaves as soon as you spot the damage. Floating row covers can prevent the adult insects from laying eggs on the plants. Insecticidal soap or neem oil can be effective against young larvae.

Rust

• What it looks like: Rusty orange, yellow, or brown pustules on leaves and stems, mostly on undersides. Leaves may 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 promptly. Avoid overhead watering. Improve air circulation around the plants. Apply sulfur or copper fungicide if needed. Don't work among wet plants. Rotate crops to prevent buildup in the soil.

Mid-Atlantic Specific Challenges: Our humid summers create the perfect environment for fungal diseases like rust, so good air circulation and avoiding overhead watering are crucial. Deer can also be a problem, so consider fencing or using deer repellent. Japanese beetles can be a nuisance, but hand-picking them off the plants or using traps can help manage the population.

Chrysanthemums benefit from companion planting. Tomatoes and peppers make good companions because they deter certain pests that might bother your mums. Lettuce is a good ground cover that will help retain moisture.

Avoid planting chrysanthemums near anything that might compete for nutrients or attract unwanted pests.