Zinnia in Zone 8A — Texas

Zinnias are a Texas gardener's dream. They explode with color all season, attracting pollinators to your garden and providing armfuls of cut flowers for your home. Plus, they thrive in our long growing season, giving you blooms from spring until the first threat of a freeze.

Our unpredictable weather can be a challenge, but zinnias are relatively easy to grow if you time things right. With our 260-day growing season, you can get two or even three flushes of blooms if you succession plant.

Starting zinnia seeds indoors gives you a head start, especially if you're aiming for that early spring bloom. Sow seeds indoors from mid February through early March, about four weeks before you plan to transplant them outside. Use seed trays with a good seed-starting mix, keep them warm, and provide plenty of light, either with a grow light or a sunny window.

Bottom watering is your friend here – set the seed trays in a shallow tray of water and let them soak it up from the bottom. This prevents damping off and keeps the seedlings happy. Since our springs can warm up quickly, starting indoors is helpful to get the jump on that early warmth.

Transplant your zinnia seedlings outdoors from mid March through mid April, after the danger of the last frost has passed. Before transplanting, harden them off by gradually exposing them to outdoor conditions for about a week. This prevents transplant shock.

Space them 6-12 inches apart in a sunny spot with well-draining soil. Keep an eye on the weather forecast; a late cold snap can happen, so be ready to cover them if necessary.

Direct sowing is a simple and effective way to grow zinnias, especially if you're not in a rush for early blooms. Sow seeds directly into the garden from mid March through early September. You have a long window here, so succession planting is easy.

Prepare the soil by loosening it and removing any weeds. Zinnias like warm soil, so wait until the soil temperature is consistently above 60°F. Plant seeds about ¼ inch deep and space them 6-12 inches apart. Keep the soil moist until they germinate.

Zinnias need moderate watering, especially during our hot Texas summers. Once established, they are somewhat drought-tolerant, but they'll bloom best with consistent moisture. Newly transplanted or direct-sown seedlings need regular watering to get established.

During the hottest part of the summer, you'll likely need to water deeply a couple of times a week, providing about an inch of water each time. Use the finger test – stick your finger about two inches into the soil. If it feels dry, it's time to water. Water at the base of the plants to avoid wetting the leaves, which can lead to powdery mildew, especially with our variable humidity.

Signs of underwatering include wilting leaves and dry soil. Overwatering can cause yellowing leaves and root rot. A layer of mulch around your plants will help retain moisture and suppress weeds, but keep it away from the stems to prevent rot.

Deadheading is key to keeping your zinnias blooming all season long. Pinch or cut off spent flowers just below the flower head, at the next set of leaves. This encourages the plant to produce more blooms. Don't be afraid to cut long stems for bouquets; the more you cut, the more the plant produces.

As the first frost approaches around mid- November, you can let the last blooms fade and save the seeds for next year.

You can expect your first zinnia harvest around mid May, about 60 days after planting. Cut flowers when they are fully open and the stems are strong. The more you cut, the more they bloom, so don't be shy!

To harvest, use sharp scissors or pruners to cut the stem at an angle. Zinnias make excellent cut flowers and have a long vase life. Just keep them watered. As the end of the season approaches and the first frost threatens, harvest any remaining blooms to enjoy indoors.

Here are three common problems you might encounter with zinnias in Texas:

• Powdery Mildew
• What it looks like: White or grayish powdery coating on leaves, stems, and sometimes buds. Leaves curl, yellow, and die.
• What causes it: Various fungi that thrive in warm days, cool nights, and moderate humidity. Dry leaf surfaces actually favor it.
• How to fix/prevent it: Improve air circulation through spacing and pruning. Remove affected leaves. Neem oil or potassium bicarbonate sprays help. Milk spray (1 part milk to 9 parts water) is surprisingly effective. Plant resistant varieties.
• Bacterial Leaf Spot
• What it looks like: Small, water-soaked spots on leaves that enlarge and turn brown or black. Spots may have a yellow halo.
• What causes it: Bacteria spread by splashing water, especially during our unpredictable rainfall and flash floods.
• How to fix/prevent it: Avoid overhead watering. Improve air circulation. Remove and destroy affected leaves. Copper-based fungicides can help prevent spread.
• Alternaria Blight
• What it looks like: Dark brown spots on leaves, often with concentric rings. Spots enlarge and can cause leaves to drop.
• What causes it: A fungus that thrives in warm, humid conditions.
• How to fix/prevent it: Improve air circulation. Remove and destroy affected leaves. Fungicides containing chlorothalonil or mancozeb can help.

Texas Specific Challenges: Our hot-to-extreme heat can stress zinnias, making them more susceptible to diseases. Variable humidity can exacerbate fungal problems. Unpredictable rainfall and flash floods can spread diseases and damage plants. Make sure to space plants adequately for good air circulation and water at the base to minimize leaf wetness.

Zinnias make great companions for many vegetables in the Texas garden. Plant them near tomatoes and peppers to attract pollinators, increasing fruit set. They also work well alongside squash and cucumbers, providing a splash of color and attracting beneficial insects that prey on pests.

Avoid planting zinnias near plants that are susceptible to powdery mildew, as they can spread the disease.