Zinnia in Zone 5B — Great Plains

Zinnias are a must-have for any Great Plains garden. Their vibrant colors bring joy, they're fantastic for cutting, and they attract pollinators like butterflies and hummingbirds. Plus, they thrive in our intense sunshine and add a burst of color from summer through fall.

Our region definitely throws some curveballs with its extreme temperature swings, occasional hail, and variable rainfall. But don't worry, with careful timing, you can absolutely grow beautiful zinnias. Our growing season, roughly 178 days, is just right for these beauties.

Starting zinnias indoors in the Great Plains isn't always necessary, but it can give you a head start, especially if we have a late spring. Starting seeds indoors from late March through mid April gives you about a 4-week jump on the season.

Use seed trays with a good seed-starting mix. Keep them warm (around 70-75°F) and provide plenty of light – a grow light works wonders. Water from the bottom to avoid damping off. Remember, our spring weather can be unpredictable, so having transplants ready can be a lifesaver if we get a late cold snap.

Transplant your zinnia seedlings outdoors from early May through early June, after the risk of frost has passed. Before transplanting, harden them off by gradually exposing them to outdoor conditions for about a week. This helps them adjust to the wind and temperature swings that are common in the Plains.

Space them 6-12 inches apart, depending on the variety. Keep an eye on the weather forecast – a late-season hailstorm can be devastating to young plants. Provide some wind protection if possible, especially for taller varieties.

Direct sowing zinnias is a simple and effective method in the Great Plains. Sow seeds from late April through early August, once the soil has warmed up to at least 60°F.

Prepare the soil by loosening it and removing any weeds. Sow seeds about ¼ inch deep and 6-12 inches apart. Keep the soil consistently moist until the seedlings emerge. Direct sowing avoids transplant shock, but you'll need to be vigilant about protecting the young plants from pests and those unpredictable spring weather events.

Watering zinnias correctly is crucial in the Great Plains, especially with our variable rainfall and hot summers. While zinnias are somewhat drought-tolerant once established, consistent watering is important, especially when they are young.

During the hottest parts of summer, you may need to water deeply 2-3 times a week, providing about 1 inch of water each time. Always check the soil moisture before watering – stick your finger about 2 inches deep; if it's dry, it's time to water. Water at the base of the plants to avoid getting the leaves wet, as wet leaves can lead to powdery mildew in our moderate humidity.

In spring and fall, when temperatures are cooler and rainfall is more frequent, you can reduce watering accordingly. Overwatering can be just as harmful as underwatering, so pay attention to the signs – yellowing leaves often indicate overwatering, while wilting leaves indicate underwatering. Mulching around the base of the plants with straw or wood chips can help retain moisture and regulate soil temperature.

Pruning zinnias is simple and rewarding. The main goal is to deadhead spent flowers to encourage more blooms.

Throughout the growing season, from late June through mid October, regularly snip off any flowers that are starting to fade. Cut the stem just above a leaf node. Don't be afraid to cut long stems for bouquets – this actually encourages the plant to produce even more flowers. As the first frost approaches in mid- October, you can cut all the remaining flowers to enjoy indoors.

You can expect your first zinnia harvest in the Great Plains starting in late June, about 60 days after planting. Zinnias are ready to harvest when the flowers are fully open and the stems are strong.

Cut the stems at an angle, as long as possible. The more you cut, the more the plant will bloom, providing you with a continuous supply of beautiful flowers throughout the summer and into the fall. As the first frost approaches in mid- October, harvest all the remaining flowers to enjoy indoors. They make excellent cut flowers with a long vase life.

Zinnias, while generally easy to grow, can sometimes be susceptible to a few problems in the Great Plains. Here are three common ones:

Powdery Mildew

• What it looks like: White or grayish powdery coating on leaves, stems, and sometimes fruit. Leaves curl, yellow, and die. Reduces plant vigor.
• What causes it: Various fungi that thrive in warm days, cool nights, and moderate humidity. Dry leaf surfaces actually favor it (unlike most fungi).
• 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, dark, water-soaked spots on the leaves, which may enlarge and merge. The spots often have a yellow halo around them.
• What causes it: Bacteria that thrive in warm, humid conditions. Splashing water from rain or irrigation can spread the bacteria.
• How to fix/prevent it: Avoid overhead watering. Improve air circulation. Remove and destroy affected leaves. Copper-based fungicides can help prevent further spread.

Alternaria Blight

• What it looks like: Circular, brown spots on the leaves, often with concentric rings. The spots may enlarge and merge, causing the leaves to yellow and die.
• What causes it: A fungus that thrives in warm, humid conditions. Spores can be spread by wind, rain, or insects.
• How to fix/prevent it: Remove and destroy affected leaves. Improve air circulation. Fungicides can help prevent further spread.

Great Plains Specific Challenges: The hot heat and variable rainfall in the Great Plains can exacerbate these problems. Be vigilant about watering at the base of the plants and providing good air circulation to minimize the risk of fungal diseases. Wind protection is also essential to prevent damage and stress, which can make plants more susceptible to disease.

Zinnias are great companions for many plants in your Great Plains garden. They attract pollinators, which benefit fruiting vegetables like tomatoes, peppers, squash, and cucumbers.

Tomatoes and peppers benefit from the increased pollination, leading to better fruit set. Squash and cucumbers also benefit from the pollinators, and the zinnias can help deter some pests. Avoid planting zinnias near plants that are susceptible to powdery mildew, as they can potentially spread the disease.