Nasturtium in Zone 7B — Southeast

Nasturtiums are worth growing here in the Southeast for their peppery flavor, versatility in the kitchen, and downright cheerful blooms. They're especially satisfying because they thrive in conditions where other plants might struggle – poor soil and even a bit of drought. Plus, they act as a trap crop for aphids, which helps protect your prized tomatoes and other veggies during our long, hot summer.

Now, we all know the Southeast can throw some curveballs with its humidity and occasional pest explosion. But with our long growing season, usually around 235 days, and reliable summer rains, you've got plenty of time to get a great crop of Nasturtiums. Careful timing and smart watering will be your best friends.

While Nasturtiums do best when direct sown, you *can* start them indoors if you're itching to get a head start. Start seeds indoors from mid February through mid March, about four weeks before you plan to transplant them outside. Use seed trays filled with a well-draining seed starting mix.

Keep the trays warm and provide plenty of light – a sunny windowsill or grow lights work well. Bottom watering is a great way to keep the soil consistently moist without overwatering, which can lead to damping off. With our moderate spring temperatures, starting indoors isn't essential, but it can give you a jump on the season.

Transplant your Nasturtium seedlings outdoors from late March through late April, after the danger of frost has passed. Before transplanting, harden off your seedlings by gradually exposing them to outdoor conditions for about a week. This helps them adjust to the sun and wind, preventing transplant shock.

Space the plants 10-12 inches apart in well-draining soil. Keep an eye on the weather forecast – those late-season cold snaps can still happen! If a freeze is predicted, cover your young plants with a frost blanket.

Direct sowing is the preferred method for Nasturtiums, as they don't always love being transplanted. Sow seeds directly into the garden from late March through early September. This gives you plenty of time to get several crops going during our long growing season.

Choose a spot with full sun to partial shade and prepare the soil by loosening it and removing any weeds. Nasturtiums aren't picky about soil, but good drainage is key, especially with our heavy clay soil. Sow seeds about ½ inch deep and 10-12 inches apart. Keep the soil consistently moist until the seedlings emerge.

Nasturtiums are drought-tolerant and actually prefer drier conditions, which is a blessing during our long, hot summers. Overwatering is a common mistake, leading to lush foliage but fewer flowers. Remember, we often get plenty of rainfall during the summer, so be mindful.

During the spring and fall, when rainfall is less frequent, check the soil moisture before watering. Stick your finger about 2 inches deep into the soil – if it feels dry, it's time to water. Aim for about 1 inch of water per week, including rainfall. In the heat of summer, you might need to water more often, but always let the soil dry out between waterings.

Water at the base of the plants to avoid wetting the foliage, which can encourage fungal diseases in our humid climate. Signs of underwatering include wilting leaves and dry, brittle stems. Overwatering can cause yellowing leaves and root rot. A layer of pine straw mulch can help retain moisture and suppress weeds, but avoid heavy mulching that keeps the soil too wet.

You can expect your first Nasturtium harvest from late May through early November, about 55 days after planting. Both the flowers and leaves are edible, so harvest as needed. The flowers are at their peak flavor when fully open.

Harvest the leaves by snipping them off at the base of the stem. For the flowers, simply pluck them off the plant. To encourage continued production, harvest regularly – this signals the plant to keep blooming. Even the seed pods can be harvested while still green and pickled like capers!

As the first frost approaches in early November, harvest any remaining flowers and leaves. The plants will likely succumb to the cold, but you can collect the mature seeds to plant again next spring.

Here are a few common problems you might encounter with Nasturtiums in the Southeast:

Aphids

• What it looks like: Clusters of small, soft-bodied insects on stems and leaves, often accompanied by sticky honeydew.
• What causes it: Aphids are attracted to lush growth, and our warm, humid climate provides ideal conditions for them to multiply.
• How to fix/prevent it: Nasturtiums are often used as a trap crop for aphids, drawing them away from your more valuable plants like tomatoes. Inspect plants regularly and blast aphids off with a strong stream of water from the hose. Insecticidal soap can also be effective.

Cabbage Caterpillars

• What it looks like: Chewed leaves, holes in foliage, and green caterpillars (like cabbage worms or cabbage loopers) on the plants.
• What causes it: These caterpillars are the larvae of cabbage white butterflies, which are common in the Southeast. They can quickly decimate your Nasturtiums.
• How to fix/prevent it: Handpick caterpillars off the plants regularly. Floating row covers can prevent the butterflies from laying eggs on your plants. *Bacillus thuringiensis* (Bt) is an effective organic treatment.

Black Fly

• What it looks like: Similar to aphids, these small black flies will gather on the stems and under leaves, sucking the sap.
• What causes it: Like aphids, they are attracted to new growth and can multiply quickly in warm, humid conditions.
• How to fix/prevent it: Blast them off with water or use insecticidal soap. Encourage beneficial insects like ladybugs, which prey on black flies.

Southeast Specific Challenges: Our hot, humid summers mean that fungal diseases can be a problem for Nasturtiums. Ensure good air circulation around your plants by spacing them properly and avoiding overhead watering. Japanese beetles can also be a nuisance, but they rarely cause significant damage to Nasturtiums. Deer, thankfully, tend to leave Nasturtiums alone.

Nasturtiums are great companions for many plants in the Southeast garden. They help deter pests and can even improve the flavor of some vegetables.

Good companions include:

• Tomatoes: Nasturtiums repel tomato hornworms and whiteflies.
• Cucumbers and Squash: They help deter squash bugs and cucumber beetles.
• Broccoli and Cabbage: They attract beneficial insects that prey on cabbage worms and other pests.

Avoid planting Nasturtiums near fennel, as it can inhibit their growth. Otherwise, they're pretty easy-going and get along well with most garden veggies.