Nasturtium in Zone 4B — Northeast

Nasturtiums are a fantastic addition to any Northeast garden, offering a peppery zing to salads and a vibrant splash of color. Their edible flowers and leaves bring a unique taste to your table, and they're surprisingly easy to grow, even with our cool nights. Plus, they're known to attract aphids away from your more prized veggies!

Our short growing season can feel daunting, but don't worry. Nasturtiums are fast growers, fitting nicely into our roughly 138-day window. With a little attention to timing, you'll be enjoying their colorful blooms and tasty leaves all summer long.

While nasturtiums thrive when direct sown, starting them indoors can give you a bit of a head start. This is particularly useful if you're aiming for the earliest possible blooms. Start your seeds indoors from mid-April through early May, about four weeks before you plan to transplant them outdoors.

Use seed trays with good drainage and a well-draining seed starting mix. Keep the soil consistently moist, and consider bottom watering to avoid damping off. A warm location and supplemental light will help those little seedlings get a strong start, ready to face our sometimes-late spring.

Once the danger of frost has passed, usually from mid-May through mid-June, it's time to transplant your nasturtium seedlings outdoors. Before planting, harden them off by gradually exposing them to outdoor conditions for about a week. This helps them adjust to the sun and wind.

Choose a sunny spot with well-drained soil. Space the plants about 10-12 inches apart to allow for their trailing growth habit. Keep an eye on the weather forecast around transplant time – a late frost can still nip young plants.

Direct sowing is the preferred method for nasturtiums, as they don't always love being transplanted. Wait until the soil has warmed up and the danger of frost is gone, typically from mid-May through mid-July. This ensures good germination.

Prepare the soil by loosening it and removing any large rocks – common in our New England gardens. Sow the seeds about ½ inch deep, spacing them 10-12 inches apart. Keep the soil consistently moist until the seedlings emerge. Nasturtiums actually prefer slightly poor soil, so don't amend it too much with compost.

Nasturtiums are surprisingly drought-tolerant and thrive with minimal watering, perfect for our Northeast summers. In fact, too much water encourages leafy growth at the expense of those beautiful, edible flowers. Less is truly more with these plants.

During the spring, when rainfall is more frequent, you likely won't need to water at all unless we're experiencing an unusually dry spell. Once summer hits and temperatures rise, check the soil moisture regularly. Use the "finger test" – if the top two inches of soil are dry, it's time to water. Aim for about an inch of water per week, delivered at the base of the plant to avoid wetting the leaves, which can lead to fungal issues in our moderate-to-humid climate.

Overwatering can lead to yellowing leaves and root rot, while underwatering will cause wilting and stunted growth. 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.

You can expect your first nasturtium harvest from mid-July through late September, about 55 days after planting. The flowers are ready to pick when they are fully open and vibrantly colored. The leaves can be harvested at any time. Even the seed pods can be harvested when they're still green and tender for pickling.

To harvest, simply snip the flowers or leaves with scissors or pinch them off with your fingers. Avoid pulling or tugging, which can damage the plant. Regular harvesting encourages more blooms and keeps the plant producing throughout the season.

As the first frost approaches in late September, harvest any remaining flowers and seed pods. The plants will likely die back after a frost, but you can collect the seeds to plant again next year.

Here are some common problems you might encounter with nasturtiums in our region:

Aphids

• What it looks like: Clusters of tiny, pear-shaped insects on stems and undersides of leaves. Leaves may be sticky or distorted.
• What causes it: Aphids thrive in warm, humid conditions, so they can be a nuisance during our Northeast summers. They're attracted to lush foliage.
• How to fix/prevent it: Nasturtiums are often used as a trap crop for aphids. You can simply let them attract the aphids away from your other plants. If the infestation gets too heavy, try blasting them off with a strong stream of water from the hose.

Cabbage Caterpillars

• What it looks like: Green caterpillars chewing holes in leaves. You may also see their droppings (frass) on the plants.
• What causes it: Cabbage white butterflies lay their eggs on nasturtiums, and the resulting caterpillars can munch on the leaves. They can be more prevalent during summers with moderate temperatures.
• How to fix/prevent it: Handpick the caterpillars off the plants and drop them into a bucket of soapy water. You can also cover your nasturtiums with row covers to prevent the butterflies from laying eggs.

Black Fly

• What it looks like: Small, black flies swarming around the plants, especially new growth. Leaves may appear stunted or distorted.
• What causes it: Black flies are attracted to moist soil and decaying organic matter. Overwatering or poor drainage can create ideal conditions for them.
• How to fix/prevent it: Improve drainage by amending the soil with compost or perlite. Avoid overwatering. You can also use yellow sticky traps to catch the adult flies.

Northeast Specific Challenges: Our moderate heat and humidity, combined with even rainfall, can create favorable conditions for pests and diseases. Keep a close eye on your plants and take action quickly to prevent problems from getting out of hand.

Nasturtiums are great companions for several plants in your Northeast garden. They attract beneficial insects and can deter pests.

Good companions include tomatoes, cucumbers, and squash. Nasturtiums can help repel squash bugs and cucumber beetles, protecting these vulnerable crops. They also work well with broccoli and cabbage, acting as a trap crop for cabbage white butterflies and their hungry caterpillars.

Avoid planting nasturtiums near fennel. Fennel can inhibit the growth of many plants, including nasturtiums, so it's best to keep them separated.