Calendula in Zone 7B — Texas

Calendula is a fantastic addition to any Texas garden. The bright, cheerful flowers are edible, medicinal, and add a pop of color that lasts through much of our long growing season. Plus, they attract beneficial insects to help with pest control, which is always a win!

Our unpredictable weather and extreme heat can be tough, but calendula is surprisingly resilient. With a little planning, you can enjoy blooms from spring all the way into fall, taking full advantage of our 255-day growing season.

Starting calendula indoors in Texas isn't always necessary, but it can give you a head start. If you're itching to get going, sow seeds indoors from early to late January, about six weeks before you plan to transplant.

Use seed trays with a good seed-starting mix, and keep them in a warm, well-lit spot. Bottom watering helps prevent damping off – just set the tray in a shallow dish of water until the soil surface is moist. With our early spring character, this can give you a jump on the season.

Transplant your calendula seedlings outdoors from late February through early April, once the danger of a hard freeze has passed. Before planting, harden them off by gradually exposing them to outdoor conditions for about a week.

Space the plants 8-12 inches apart in well-draining soil. Keep an eye on the forecast – those late-season cold snaps can still happen! Be ready to cover your young plants if temperatures dip unexpectedly.

Direct sowing calendula is easy and often the preferred method for many Texas gardeners. Sow seeds directly into the garden from late February through late September. This wide window takes advantage of our long growing season.

Prepare the soil by loosening it and removing any weeds. Sow seeds about ¼ inch deep and keep the soil consistently moist until they germinate. Thin seedlings to 8-12 inches apart. Direct sowing avoids transplant shock and allows the plants to establish strong root systems right away.

Calendula needs moderate watering, especially during our hot Texas summers. While it can tolerate some drought, consistent moisture encourages more blooms.

During the spring and fall, when temperatures are milder, water deeply once or twice a week, providing about an inch of water each time. In the heat of summer, you might need to water every other day, or even daily, depending on rainfall and soil drainage. The "finger test" is your friend: stick your finger about two inches deep into the soil. 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, especially with our variable humidity.

Signs of underwatering include wilting leaves and stunted growth. Overwatering can lead to root rot, indicated by yellowing leaves and a mushy stem base. A layer of mulch around your plants helps retain moisture and keeps the soil cooler, which is especially beneficial during our brutal summer heat.

Deadheading is key to keeping your calendula plants blooming throughout the season. Regularly remove spent flowers to encourage the plant to produce more.

Simply pinch or cut off the flower heads just below the bloom. Leaving some flowers to mature will allow the plant to self-seed, giving you volunteers next year. As the first frost approaches in mid- November, you can let the remaining flowers go to seed, or pull the plants if you prefer.

You can expect your first calendula harvest about 45 days after planting, typically from early April through late November in Texas. Harvest the flowers when they are fully open and the petals are at their peak color.

Gently pinch or cut the flower heads from the stem, being careful not to damage the plant. Regular harvesting encourages continuous production. The petals can be used fresh or dried for various culinary and medicinal purposes. As the first frost approaches in mid- November, harvest any remaining blooms to preserve before the cold weather sets in.

Here are some common problems you might encounter with calendula in Texas:

Powdery Mildew

• What it looks like: White or grayish powdery coating on leaves, stems, and sometimes flower buds. Leaves may curl, yellow, and eventually die, reducing the plant's overall vigor.
• What causes it: Various fungi that thrive in warm days, cool nights, and moderate humidity. Surprisingly, dry leaf surfaces actually favor powdery mildew.
• How to fix/prevent it: Improve air circulation by spacing plants adequately and pruning dense foliage. Remove and discard affected leaves promptly. Neem oil or potassium bicarbonate sprays can help control the spread. A milk spray (1 part milk to 9 parts water) is also surprisingly effective.

Aphids

• What it looks like: Clusters of tiny, soft-bodied insects (green, black, or white) on stems and the undersides of leaves. Sticky honeydew residue on foliage. Curled or distorted new growth.
• What causes it: Rapidly reproducing sap-sucking insects. Populations tend to explode during warm weather. Ant colonies may farm them for the honeydew they produce.
• How to fix/prevent it: A strong spray of water from your hose can knock aphids off the plants. Encourage natural predators like ladybugs and lacewings. Insecticidal soap is effective for heavy infestations. Neem oil works systemically to disrupt their life cycle.

Whiteflies

• What it looks like: Tiny, white, moth-like insects that fly up in a cloud when disturbed. Yellowing or silvering of leaves. Sticky honeydew residue.
• What causes it: Sap-sucking insects that thrive in warm, humid conditions. They weaken plants by feeding on their sap.
• How to fix/prevent it: Hang yellow sticky traps to catch adult whiteflies. Spray plants with insecticidal soap or neem oil, paying close attention to the undersides of leaves where they congregate. Vacuuming the plants can also help reduce their numbers.

Texas Specific Challenges: Our hot-to-extreme heat can stress calendula, making them more susceptible to pests and diseases. Variable humidity and unpredictable rainfall can exacerbate fungal issues like powdery mildew. Proper watering and good air circulation are crucial for keeping your plants healthy.

Calendula makes a great companion plant in the Texas garden. Plant them near tomatoes and peppers to attract beneficial insects that prey on common pests like aphids and tomato hornworms.

They also do well planted near green beans, as they attract pollinators that can increase bean production. Avoid planting calendula near cabbage family plants, as they can attract cabbage moths, which can then damage your brassicas.