French Marigold in Zone 9A — Desert Southwest

French Marigolds are a fantastic addition to any Desert Southwest garden. Their bright, cheerful blooms add a pop of color and their scent can help deter pests from your more prized veggies. Plus, they're relatively low-maintenance, making them perfect for our busy spring and fall growing seasons.

Sure, desert gardening comes with its own set of challenges like extreme heat and alkaline soil. But with a long growing season of around 298 days and some strategic timing, you can easily enjoy these beauties in your garden.

Starting French Marigold seeds indoors isn't essential in our climate, but it can give you a head start, especially for a very early spring bloom. If you want to get a jump on the season, sow seeds indoors from mid January through early February, about six weeks before you plan to transplant them.

Use seed trays with a good seed-starting mix and keep them in a warm, well-lit area. Bottom watering is key to prevent damping off – set the tray in a shallow dish of water until the surface of the soil is moist. Given our very-early spring character, this can help you get blooms before the extreme heat hits.

Transplant your French Marigold seedlings outdoors from early March through mid April, after the last expected frost. Before planting, harden them off by gradually exposing them to outdoor conditions for about a week. This helps them adjust to the intense Desert Southwest sun and fluctuating temperatures.

Space them 8-10 inches apart in well-draining soil. Keep a close eye on the weather forecast for any late cold snaps, and be ready to cover them if needed, especially if a temperature swing is headed our way.

Direct sowing French Marigold seeds is a simple and effective method in our region, and it lets you take full advantage of both of our growing seasons. You can direct sow from mid February through early October, giving you plenty of flexibility. Keep in mind that summer survival is the goal for plants started in late spring.

Prepare your soil by loosening it and removing any rocks or debris. Sow seeds about ¼ inch deep and keep the soil consistently moist until they germinate. Thin seedlings to 8-10 inches apart once they emerge.

French Marigolds are surprisingly drought-tolerant once established, making them a great choice for water-wise desert gardening. During the cooler spring and fall months, water deeply about once a week, or whenever the top two inches of soil feel dry to the touch. This is where the "finger test" comes in handy.

During the extreme heat of summer, you might need to increase watering to two or three times a week, especially for plants in full sun. Aim for about an inch of water per week, delivered at the base of the plant to avoid wetting the foliage. Our arid climate helps to minimize fungal issues, but it's still best to avoid overhead watering.

Look for signs of underwatering, such as wilting leaves and dry soil, or overwatering, which can lead to yellowing leaves and root rot. A layer of mulch around your plants will help retain moisture and keep the soil cool, but be sure to use a mulch that doesn't raise the soil's pH.

Deadheading is the key to keeping your French Marigolds blooming throughout our long growing season. Regularly remove spent flowers by snipping them off just below the flower head. This encourages the plant to produce more blooms instead of putting energy into seed production.

You can deadhead anytime during the growing season, whenever you see faded or dried-up flowers. As the first frost approaches in early December, stop deadheading and allow the last flowers to mature and produce seeds. You can then collect these seeds to plant next year.

You can expect your first harvest of French Marigold blooms about 50 days after planting, which means from early April through early December, depending on when you sowed your seeds. Harvest the flowers when they are fully open and the petals are vibrant.

To harvest, simply snip the stem just below the flower head. Regular harvesting encourages the plant to produce even more flowers. As the end of the season approaches and temperatures drop, you can still harvest flowers until the first hard frost.

If you want to save seeds for next year, allow some of the flower heads to dry completely on the plant. Once they are dry and brown, you can collect the seeds from the center of the flower head. Store the seeds in a cool, dry place until planting time.

Spider Mites:

• What it looks like: Fine webbing on the plant, tiny yellow or brown spots on the leaves, and overall leaf discoloration.
• What causes it: Hot, dry conditions create the perfect environment for spider mites to thrive. Our low humidity stress makes them especially problematic.
• How to fix/prevent it: Increase humidity around the plants by misting them regularly. You can also use insecticidal soap or neem oil to control infestations. A strong blast of water from the hose can also dislodge them.

Powdery Mildew:

• What it looks like: White or grayish powdery coating on leaves, stems. 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 (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.

Slugs:

• What it looks like: Holes in the leaves of young plants, slimy trails on the soil.
• What causes it: Slugs are attracted to moist environments and can be a problem, especially during our monsoon moisture season.
• How to fix/prevent it: Handpick slugs from your plants, especially at night. You can also use slug bait or create barriers around your plants with copper tape or diatomaceous earth.

Desert Southwest Specific Challenges: The extreme heat and intense sun can stress French Marigolds, making them more susceptible to pests and diseases. Providing afternoon shade during the hottest months can help. While our arid humidity usually keeps fungal diseases at bay, occasional monsoon rainfall can create favorable conditions for powdery mildew.

French Marigolds are great companions for many plants in your Desert Southwest garden. Plant them near tomatoes and peppers to help deter nematodes and other soil pests. They also attract beneficial insects like ladybugs and hoverflies, which can help control aphids and other garden pests.

Basil also benefits from being planted near marigolds, as the marigolds help to repel basil-loving pests. Cucumber can also benefit as marigolds deter squash bugs. However, avoid planting French Marigolds near beans-green, as they can inhibit their growth.