Nasturtium in Zone 7A — Pacific Northwest

Nasturtiums are fantastic for any Pacific Northwest garden. The peppery flavor of the leaves and flowers adds a zing to salads, and they're incredibly versatile in the kitchen. Plus, they're just plain cheerful, adding a splash of color to your garden, even on our overcast spring days.

Our mild summers can be a bit of a balancing act for some plants, but nasturtiums handle it beautifully. With our 183-day growing season, you'll have plenty of time to enjoy them, especially since they don't mind the cooler nights we often get.

While nasturtiums are happiest when direct-sown, starting them indoors gives you a jump start, especially if you want early blooms. Start seeds indoors from late March through mid April, about four weeks before you plan to transplant. Use seed trays with a good seed-starting mix, and keep them in a warm spot with plenty of light, either from a sunny window or a grow light.

Keep the soil consistently moist, but not soggy; bottom watering can help prevent damping-off. Remember, our springs here in the PNW can be slow to warm up, so indoor starting gives your nasturtiums a head start against the cool soil.

Transplant your nasturtium seedlings outdoors from late April through late May, once the danger of frost has passed. Before planting, harden them off by gradually exposing them to outdoor conditions for about a week. This helps them adjust to the cooler temperatures and stronger sunlight.

When transplanting, space them about 10-12 inches apart. Keep an eye on the forecast – a late cold snap can still happen, so be ready to cover them if needed.

Direct sowing is the preferred method for nasturtiums since they resent transplanting. Wait until late April, after the last expected frost, to direct sow. You can continue sowing seeds through mid August for a continuous supply of flowers and leaves.

Prepare the soil by loosening it and removing any weeds. Nasturtiums aren't picky about soil, but good drainage is important. Sow seeds about half an 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 drought-tolerant and actually thrive on neglect, making them perfect for our dry summer months in the PNW. Overwatering can lead to more foliage than flowers, so less is definitely more. During our wet springs, you likely won't need to water them at all.

Once the dry summer hits, check the soil moisture with the finger test: stick your finger about two inches deep into the soil. If it feels dry, it's time to water. Aim for about an inch of water per week during dry spells, but only if the soil is truly dry. Water at the base of the plant to avoid wetting the foliage, which can help prevent fungal issues in our sometimes humid conditions.

Signs of underwatering include wilting leaves and stunted growth. Overwatering can cause yellowing leaves and root rot. A light layer of mulch, like composted leaves, can help retain moisture in the soil during the driest periods, but avoid heavy mulching, which can keep the soil too wet.

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

To harvest, simply snip the flowers or leaves with scissors or your fingers. Avoid pulling or tugging, which can damage the plant. Regularly harvesting the flowers encourages the plant to produce more blooms.

As the first frost approaches in mid- October, harvest any remaining flowers and seed pods. The seed pods can be pickled for a caper-like treat, extending your harvest even further.

Nasturtiums are generally easy to grow, but here are a few common problems you might encounter in the Pacific Northwest:

Aphids

• What it looks like: Clusters of tiny green, black, or brown insects on stems and leaves. Leaves may be sticky or distorted.
• What causes it: Aphids are attracted to new growth and can multiply quickly, especially during mild weather. They're common in our springs.
• How to fix/prevent it: Nasturtiums are often used as a trap crop for aphids, drawing them away from other plants. You can also spray them off with a strong stream of water or use insecticidal soap.

Cabbage Caterpillars

• What it looks like: Holes in leaves, often with green or brown caterpillars present.
• What causes it: These caterpillars are the larvae of cabbage white butterflies, which are common in our region.
• How to fix/prevent it: Handpick caterpillars off the plants. Cover plants with netting to prevent butterflies from laying eggs. Bacillus thuringiensis (Bt) is an effective organic treatment.

Black Fly

• What it looks like: Similar to aphids, but black in color and often found on new growth.
• What causes it: Similar to aphids, they thrive in mild conditions and can quickly infest plants.
• How to fix/prevent it: Use the same methods as for aphids: strong sprays of water, insecticidal soap, or introduce beneficial insects like ladybugs.

Pacific Northwest Specific Challenges: Our mild heat and moderate humidity during the summer months generally favor nasturtiums. However, watch out for late blight, which can spread from nearby tomatoes and potatoes; good air circulation is key. Slugs can also be a problem, especially in wet springs.

Nasturtiums are great companions for many plants in the Pacific Northwest garden:

• Tomatoes: Nasturtiums repel tomato hornworms and other pests, protecting your tomato crop.
• Cucumbers and Squash: They deter squash bugs and vine borers, common pests for these plants.
• Broccoli and Cabbage: Nasturtiums attract beneficial insects that prey on cabbage moths and other cabbage-family pests.

Avoid planting nasturtiums near fennel, as it can inhibit their growth.