Chrysanthemum in Zone 5B — Midwest

Chrysanthemums are a fantastic addition to any Midwest garden, bringing vibrant fall color when many other plants are fading. Their daisy-like blooms come in a huge range of colors and sizes, making them perfect for adding pops of color to your borders or cut flower arrangements. Plus, they're relatively easy to grow, offering great satisfaction for gardeners of all levels.

Our Midwest weather can be unpredictable, with temperature swings in spring and the occasional summer heat spell. Luckily, Chrysanthemums are pretty resilient, and by starting them indoors at the right time and providing the proper care, you can enjoy a beautiful display throughout our 168-day growing season.

Starting Chrysanthemums indoors is an option, especially if you want a head start on the season, though many Midwest gardeners find success buying established plants. If you choose to start from seed, aim to do so from late February through mid March, about 8 weeks before you plan to transplant them outdoors.

Use seed trays with a good seed-starting mix and keep them in a warm location, ideally around 70°F. A heat mat can be helpful, especially in our sometimes-cool Midwest springs. Provide plenty of light – a grow light is best, as our natural light can be limited this time of year. Water from the bottom by setting the tray in a shallow dish of water until the soil surface is moist; this helps prevent damping off.

Transplant your Chrysanthemums outdoors from late April through late May, once the danger of frost has passed. Our springs can be variable, so keep an eye on the forecast and be prepared to cover your plants if a late frost threatens. Before transplanting, harden off your seedlings by gradually exposing them to outdoor conditions for about a week.

Choose a sunny spot with well-draining soil and space the plants 12-18 inches apart. Amending our clay soil with compost before planting will help with drainage and provide essential nutrients. Alternatively, you can find potted mums in fall, or starts in spring, at local nurseries.

Chrysanthemums need consistent moisture, but they don't like to be waterlogged, so finding the right balance is key, especially with our wet-summer rainfall patterns here in the Midwest. During the active growing season, from spring through summer, aim to water deeply about once a week, providing roughly 1 inch of water.

Check the soil moisture before watering by sticking your finger about 2 inches deep – if it feels dry, it's time to water. Water at the base of the plant to avoid wetting the foliage, which can encourage fungal diseases in our moderate-to-humid climate. During summer heat spells, you may need to water more frequently.

Signs of underwatering include wilting leaves and dry, crispy edges. Overwatering can lead to yellowing leaves and root rot. A layer of mulch around the base of the plants will help retain moisture and suppress weeds, which is especially helpful in our Midwest gardens.

Pinching your Chrysanthemums is essential for creating bushy plants with abundant blooms. Starting when the plants are about 6 inches tall, pinch off the growing tips every 2-3 weeks. This encourages the plants to branch out and produce more flowering stems.

Make sure to stop pinching around July 4th. After this date, the plants need to start setting flower buds for their fall display. As the first frost approaches around early October, you can cut back the plants to about 6 inches above the ground.

Your Chrysanthemums will typically begin blooming from early July through late August, depending on the variety and when you transplanted them. These are fall-blooming plants, so expect most of the color later in the season. The flowers last for weeks in the garden, providing a beautiful display.

When cutting flowers for bouquets, choose blooms that are fully open. Use clean, sharp snips to avoid damaging the plant. Cutting the flowers encourages the plant to produce more blooms, so don't be afraid to harvest generously.

As the first frost approaches in early October, harvest any remaining blooms you want to enjoy indoors. While Chrysanthemums are hardy, the frost will damage the flowers.

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

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.
• What causes it: Larvae of small flies that burrow between the leaf surfaces to feed.
• How to fix/prevent it: Remove and destroy affected leaves. Cover plants with row covers to prevent flies from laying eggs. Insecticidal soap or neem oil can help with heavy infestations.

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.

Midwest Specific Challenges: Our moderate-to-hot heat and moderate-to-humid humidity, combined with wet-summer rainfall, create conditions that can favor fungal diseases like rust. Good air circulation and avoiding overhead watering are crucial preventative measures. Monitor your plants regularly and address any problems promptly to keep them healthy and thriving.

Chrysanthemums benefit from companion planting in the Midwest garden. Tomatoes and peppers make good companions because they deter pests like aphids that can bother Chrysanthemums. Lettuce can also be a good choice, as it provides ground cover that helps retain moisture and suppress weeds, especially helpful in our sometimes-clay soil.

Avoid planting Chrysanthemums near plants that are susceptible to similar pests or diseases.