Nasturtium in Zone 4A — Northeast

Nasturtiums are a fantastic addition to any Northeast garden. Their peppery leaves and bright flowers add a unique flavor to salads, plus they're beautiful and attract pollinators. Given our cool nights and moderate summer temperatures, Nasturtiums produce flavorful leaves and plenty of blooms right up until frost.

Our short growing season means we have to be strategic, but Nasturtiums are quick to mature. With a little planning, you can easily enjoy a long harvest from mid-summer until the first frost in mid-September. Even with our 128-day growing season, you'll have plenty of time to savor these beauties.

While Nasturtiums prefer direct sowing, starting them indoors is possible if you want a head start. Begin in mid-April through early May, about four weeks before you plan to transplant. Use seed trays filled with a good seed-starting mix, and keep them warm and well-lit.

Bottom watering is a great way to keep the soil moist without overwatering, which Nasturtiums dislike. Given our late springs in the Northeast, starting indoors can give you a jump, but be gentle when transplanting, as they don't love having their roots disturbed.

Transplant your Nasturtium seedlings outdoors in late May through mid-June, once the danger of frost has passed. Before transplanting, harden them off by gradually exposing them to outdoor conditions for about a week. This helps them adjust to the cooler Northeast nights and stronger sunlight.

Space them 10-12 inches apart in your garden. Keep an eye on the weather forecast, as we can sometimes get a late frost even in early June. Be ready to cover your seedlings if needed.

Direct sowing is the preferred method for Nasturtiums, as they resent transplanting. Wait until late May through mid-July, after the last frost, to sow your seeds directly into the garden. The soil should be at least 60°F for best germination.

Prepare your soil by loosening it and removing any large rocks – common in our rocky New England soil. Sow seeds 1/2 inch deep and space them 10-12 inches apart. Keep the soil consistently moist until the seedlings emerge, usually in about a week.

Nasturtiums thrive in poor, dry soil, so avoid the urge to overwater them. Too much water or fertilizer encourages leaf growth at the expense of flowers – and we want those beautiful, edible blooms! In our moderate-to-humid Northeast climate, less is definitely more.

During the peak of summer, when temperatures reach the low 80s, check the soil moisture using the "finger test." Stick your finger about two inches into the soil; if it feels dry, it's time to water. Aim for about one inch of water per week, either from rainfall or irrigation. Water at the base of the plants to avoid wetting the leaves, which can promote fungal diseases in our moderately humid environment.

Signs of underwatering include wilting leaves and a lack of flowers. Overwatering can lead to yellowing leaves and root rot. A light layer of mulch, like straw or shredded leaves, can help retain moisture without waterlogging the soil, which is particularly useful given our even rainfall patterns.

You can expect your first harvest of Nasturtium flowers and leaves from mid-July through mid-September, about 55 days after planting. The flowers are ready to harvest when they are fully open and vibrantly colored. The leaves are best when young and tender.

Harvest flowers and leaves by snipping them off with scissors or pinching them off with your fingers. Avoid pulling or tugging, which can damage the plant. Regularly harvesting encourages continued production.

As our first frost approaches in mid-September, harvest any remaining flowers and seed pods. The seed pods can be pickled and used like capers, extending your harvest season even further.

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

Aphids (intentional trap crop)

• What it looks like: Clusters of small, soft-bodied insects, usually green or black, on stems and undersides of leaves. Leaves may be sticky or distorted.
• What causes it: Aphids are attracted to Nasturtiums, often acting as a trap crop to draw them away from other plants. Warm, humid conditions can encourage aphid populations.
• How to fix/prevent it: Check plants regularly and wash off aphids with a strong stream of water. Introduce beneficial insects like ladybugs. Consider using insecticidal soap if infestations are heavy, but remember you are growing these for food.

Cabbage Caterpillars

• What it looks like: Green caterpillars that chew holes in leaves. You might also see their droppings (frass) on the plants.
• What causes it: Cabbage white butterflies lay their eggs on Nasturtiums, and the caterpillars hatch and feed on the leaves.
• How to fix/prevent it: Handpick caterpillars off the plants. Cover plants with row covers to prevent butterflies from laying eggs. Bacillus thuringiensis (Bt) is an effective organic treatment.

Black Fly

• What it looks like: Tiny black flies swarming around the plants, particularly in damp conditions.
• What causes it: Poor air circulation and overly moist soil can attract black flies.
• How to fix/prevent it: Improve air circulation by spacing plants properly. Avoid overwatering and ensure good drainage. Use sticky traps to catch adult flies.

Northeast Specific Challenges: Our moderate heat, moderate-to-humid humidity, and even rainfall can create ideal conditions for some pests and diseases. Regular monitoring and good cultural practices, such as proper spacing and watering, are key to keeping your Nasturtiums healthy and productive in our Northeast climate.

Nasturtiums are great companion plants for many vegetables in a Northeast garden. They attract beneficial insects and can even act as a trap crop for aphids, protecting your other plants.

Good companions include tomatoes, cucumbers, squash, broccoli, and cabbage. Nasturtiums help deter pests that often plague these crops. For example, planting them near tomatoes can help repel tomato hornworms. They also attract pollinators, which are essential for cucumbers and squash. Avoid planting them near fennel, as they can inhibit each other's growth.