Nasturtium in Zone 6A — Mid-Atlantic

Nasturtiums are a fantastic addition to any Mid-Atlantic garden. Their peppery leaves and bright flowers add a unique flavor to salads, and they're incredibly versatile in the kitchen. Plus, they're just plain cheerful to look at, thriving beautifully in our humid summers and adding a splash of color right up until frost.

Our four seasons can be a bit unpredictable, but Nasturtiums are surprisingly resilient. With our long 188-day growing season, you'll have plenty of time to enjoy these beauties, even with the occasional late frost or early heat wave we sometimes experience.

Starting Nasturtiums indoors isn't essential, given how well they direct sow, but it can give you a head start. If you want to get a jump on the season, aim to start your seeds indoors from mid-March through early April, about four weeks before you plan to transplant them outdoors.

Use seed trays with a good seed-starting mix, and keep them warm and well-lit – a simple grow light works wonders. One trick I've found helpful is to bottom water the trays to encourage strong root growth and prevent damping off, which can be a problem in our moderate spring.

Transplanting Nasturtiums should happen from late April through mid-May, once the danger of frost has passed. Before you move them outdoors permanently, be sure to harden them off. Give them a week of gradual exposure to the elements, starting with just a few hours a day in a sheltered spot.

When transplanting, space them about 10-12 inches apart. Keep an eye on the weather forecast, as we sometimes get unexpected cold snaps in late spring, so be ready to cover them if needed.

Direct sowing is the way to go with Nasturtiums. They really don't like being transplanted, so popping the seeds directly into the garden is your best bet. You can direct sow from late April through mid-August, giving you a long window to get them in the ground.

Make sure the soil is relatively warm – at least 60°F – before sowing. Prepare the soil by loosening it up and removing any large clumps. Plant the seeds about half an inch deep, spacing them 10-12 inches apart. They'll germinate quickly and get growing as soon as the soil warms up.

Nasturtiums are surprisingly drought-tolerant, which is great for our Mid-Atlantic summers. While we get reliable rainfall, there are definitely stretches where things get dry, and these plants can handle it. The key is not to overwater them, as too much moisture can lead to more foliage than flowers.

During the hotter parts of summer, give them about an inch of water per week if it hasn't rained. Use the finger test: stick your finger about two inches into the soil, and if it feels dry, it's time to water. Water at the base of the plants to avoid wetting the leaves, which can encourage fungal diseases in our humid climate. Signs of underwatering include wilting leaves, while yellowing leaves can indicate overwatering. A light layer of mulch can help retain moisture without making the soil soggy.

You can expect your first harvest of Nasturtium flowers and leaves from mid-June through mid-October, about 55 days after planting. The flowers are ready to pick when they are fully open and brightly colored. The leaves can be harvested at any time.

When harvesting, gently snip the stems with scissors or pruning shears to avoid damaging the plant. Regular harvesting encourages more blooms. As we approach the first frost in mid-October, harvest any remaining flowers and seed pods to use in the kitchen or preserve for later. The green seed pods can be pickled like capers.

Here are a few common problems you might encounter with Nasturtiums in the Mid-Atlantic:

Aphids

• What it looks like: Clusters of tiny green, black, or brown bugs on stems and leaves, often causing distorted or yellowing foliage.
• What causes it: Aphids are attracted to stressed plants. In our region, early season temperature swings can weaken young plants.
• How to fix/prevent it: Nasturtiums are often used as a trap crop for aphids, drawing them away from other plants. You can also blast them off with a strong stream of water or introduce beneficial insects like ladybugs.

Cabbage Caterpillars

• What it looks like: Holes in the leaves, often with green caterpillars visible.
• What causes it: These caterpillars are the larvae of cabbage white butterflies, which are common in our area.
• How to fix/prevent it: Handpick the caterpillars off the plants or use a row cover to prevent the butterflies from laying their eggs. Bacillus thuringiensis (Bt) is also an effective organic control.

Black Fly

• What it looks like: Small, dark, fly-like insects clustered on new growth, causing stunted or distorted leaves.
• What causes it: Humid conditions, common in our Mid-Atlantic summers, favor black fly infestations.
• How to fix/prevent it: Increase air circulation around the plants by spacing them properly. Insecticidal soap can be effective, but use it cautiously as it can also harm beneficial insects.

Mid-Atlantic Specific Challenges: The combination of moderate-to-hot heat and high humidity in our summers can create conditions that favor fungal diseases and pest infestations. Be sure to provide good air circulation and avoid overwatering to keep your Nasturtiums healthy.

Nasturtiums make great companions for many plants in the Mid-Atlantic garden. They attract beneficial insects and can even act as a trap crop for pests. They do particularly well near tomatoes, cucumbers, and squash, as they can help deter squash bugs and other pests that plague these crops. They also benefit broccoli and cabbage by attracting cabbage white butterflies away from these brassicas. Avoid planting them near fennel, as fennel can inhibit the growth of many plants.