Nasturtium in Zone 5B — Mid-Atlantic

Nasturtiums are a fantastic addition to any Mid-Atlantic garden. Their peppery leaves and vibrant flowers add a unique zest to salads, plus they attract beneficial insects. It's incredibly rewarding to have such an easy-to-grow edible flower that thrives in our four-season climate.

While our humid summers and occasional deer pressure can present challenges, nasturtiums are surprisingly resilient. You'll find they fit right into our 178-day growing season. With a little attention to timing, you can enjoy a steady supply of colorful blooms and tasty leaves.

Starting nasturtiums indoors is possible, but not usually necessary in our Mid-Atlantic climate. Since they resent transplanting, direct sowing is generally preferred. However, if you want a head start or have a particularly short growing season due to microclimate issues, you can start seeds indoors late March through mid April, about four weeks before the last expected frost.

Use seed trays filled with a well-draining potting mix. Keep them warm (around 70°F) and provide plenty of light, either from a sunny windowsill or a grow light. A helpful tip is to water your seedlings from the bottom, by placing the tray in a shallow dish of water, to encourage strong root growth. Our springs here in the Mid-Atlantic are moderate, so keep an eye on the weather and be ready to adjust your plans if temperatures swing.

If you started your nasturtiums indoors, it's time to think about transplanting them outdoors late April through late May. Before transplanting, harden off your seedlings by gradually exposing them to outdoor conditions for about a week. This prevents shock and helps them acclimate to our Mid-Atlantic weather.

Choose a sunny spot with well-drained soil, spacing the plants 10-12 inches apart. Keep an eye on the forecast. We sometimes have unexpected cool snaps during this period, so be prepared to cover your seedlings if a late frost is predicted.

Direct sowing is the easiest and most successful way to grow nasturtiums in our area. Wait until the danger of frost has passed, typically late April, and you can continue sowing seeds through early August for a continuous harvest. Nasturtiums germinate best when the soil temperature is around 65-70°F.

Prepare the soil by loosening it and removing any weeds. You don't need to amend it much, as nasturtiums actually prefer slightly poor soil. Sow seeds about ½ inch deep, spacing them 10-12 inches apart. Keep the soil consistently moist until the seedlings emerge, which usually takes about a week or two.

Nasturtiums are quite drought-tolerant, which is a bonus during our humid summers here in the Mid-Atlantic. Overwatering can actually be detrimental, leading to more foliage than flowers. So, the key is to water judiciously.

During the spring, with our even rainfall, you may not need to water at all unless we experience a dry spell. Once the summer heat kicks in (typical highs around 88°F), check the soil moisture regularly. 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, either from rainfall or irrigation. 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 stunted growth. Overwatering can lead to yellowing leaves and root rot. A light layer of mulch around the base of the plants can help retain moisture and suppress weeds, but be careful not to overdo it, as too much mulch can also contribute to excessive moisture.

You can expect your first harvest of nasturtium flowers and leaves about 55 days after planting, typically starting in late June and continuing through mid October. The flowers are ready to harvest when they are fully open and brightly colored. The leaves can be harvested at any time.

To harvest, simply snip the flowers or leaves from the plant with scissors or your fingers. Regular harvesting encourages continued production. As we approach mid- October and the threat of our first frost looms, harvest any remaining flowers and leaves. You can even pickle the green seed pods as a caper substitute.

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 insects on stems and leaves, often causing distorted growth.
• What causes it: Aphids are attracted to stressed plants, and our variable spring weather can sometimes weaken young nasturtiums.
• How to fix/prevent it: Nasturtiums are often used as a trap crop for aphids, drawing them away from other vegetables. Blast them off with a strong stream of water from the hose. You can also introduce beneficial insects like ladybugs.

Cabbage Caterpillars

• What it looks like: Holes in leaves, often accompanied by green caterpillars.
• What causes it: These caterpillars are the larvae of cabbage white butterflies, which are common in our region.
• How to fix/prevent it: Handpick the caterpillars off the plants. You can also use row covers to prevent the butterflies from laying eggs.

Black Fly

• What it looks like: Tiny black flies swarming around the plants, especially new growth.
• What causes it: These pests thrive in humid conditions, which we certainly have during our Mid-Atlantic summers.
• How to fix/prevent it: Improve air circulation around the plants by spacing them properly. You can also use insecticidal soap or neem oil, but be mindful of beneficial insects.

Mid-Atlantic Specific Challenges: Our moderate-to-hot summer heat and humid humidity can create favorable conditions for pests and diseases. Regular monitoring and good air circulation are key to keeping your nasturtiums healthy. Even rainfall is generally beneficial, but be mindful of overwatering, especially in heavy clay soils.

Nasturtiums make excellent companion plants in the Mid-Atlantic garden. They attract pollinators and beneficial insects, and can even repel certain pests.

Good companions include tomatoes, cucumbers, and squash. Nasturtiums help protect these plants from aphids and squash bugs. They also work well with broccoli and cabbage, deterring cabbage moths. Avoid planting nasturtiums near fennel, as they can compete for resources.