Nasturtium in Zone 8B — Pacific Northwest

Nasturtiums are a fantastic addition to any Pacific Northwest garden. Their peppery leaves and vibrant flowers add a unique flavor to salads, while the bright colors bring beauty to your garden. Plus, they’re incredibly easy to grow, offering a rewarding experience even for beginner gardeners in our mild climate.

While we sometimes struggle with getting enough heat for certain crops, Nasturtiums thrive in our longer, cooler growing season. With a growing season that stretches from early June to late October, you'll have plenty of time to enjoy these beauties.

Starting Nasturtiums indoors isn’t strictly necessary in our Zone 8B climate, but it can give you a head start, especially if we have a cool, wet spring. If you want to get a jump on things, start your seeds indoors from early to late March, about four weeks before you plan to transplant.

Use seed trays filled with well-draining potting mix and provide gentle bottom watering to avoid damping off, which can be a problem during our overcast spring days. Ensure they have a warm spot and plenty of light, either from a sunny window or a grow light, until they're ready to go outside.

Transplant your Nasturtium seedlings outdoors from mid April through early May, once the risk of frost has passed. Be sure to harden them off first by gradually exposing them to outdoor conditions for about a week.

Space them about 10-12 inches apart to give them room to spread. Keep an eye on the weather forecast – those late spring cold snaps can still surprise us!

Direct sowing is the preferred method for Nasturtiums, as they don't always love being transplanted. You can direct sow from mid April through late August, giving you a long window of opportunity here in the PNW.

Choose a spot with full sun to partial shade and ensure the soil is relatively warm. Prepare the soil by loosening it and removing any large rocks or debris. Sow seeds about ½ inch deep and 10-12 inches apart. Keep the soil consistently moist until the seedlings emerge.

Nasturtiums are wonderfully drought-tolerant and actually prefer slightly drier conditions, which is perfect for our dry summer months. Overwatering can lead to more foliage and fewer flowers, so less is definitely more.

During our wet springs, you likely won't need to water them at all. Once our dry summer months arrive, check the soil moisture about 2 inches deep – the "finger test." If the soil is dry to the touch, give them a good soak, aiming for about 1 inch of water per week. Water at the base of the plants to avoid wetting the foliage, which can encourage fungal diseases.

Signs of underwatering include wilting leaves and stunted growth. Overwatering can cause yellowing leaves and root rot. A light layer of mulch, like bark chips, can help retain moisture during the drier months, but be careful not to overdo it.

You can expect your first harvest of Nasturtium flowers and leaves around early June if you started early, and you can continue harvesting through early November thanks to our long, mild fall. These plants really produce for us in the PNW.

The flowers are ready to harvest when they are fully open and vibrantly colored. Simply snip them off with scissors or pinch them off with your fingers. For the leaves, harvest them as needed, taking care not to remove too many from one plant at a time. The seed pods can be harvested when they are green and plump, perfect for pickling.

Regular harvesting encourages more flower and leaf production. As the first frost approaches in early November, harvest any remaining flowers and seed pods to preserve their flavor and beauty.

Here are a few common issues you might encounter with Nasturtiums in the Pacific Northwest:

Aphids

• What it looks like: Clusters of small, soft-bodied insects on stems and leaves, often accompanied by sticky honeydew and sooty mold.
• What causes it: Aphids are attracted to stressed plants, and our cool, wet springs can sometimes weaken young seedlings.
• How to fix/prevent it: Nasturtiums are often used as a trap crop to draw aphids away from other plants. You can also spray them off with a strong jet of water or use insecticidal soap.

Cabbage Caterpillars

• What it looks like: Holes in leaves, often with green or brownish caterpillars present.
• 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 or cover them with netting to prevent butterflies from laying eggs.

Black Fly

• What it looks like: Small black flies clustered around new growth, causing distorted or stunted leaves.
• What causes it: Like aphids, black flies are attracted to stressed plants and can thrive in our moist spring conditions.
• How to fix/prevent it: Improve air circulation around the plants and spray with insecticidal soap.

Pacific Northwest Specific Challenges: Our mild heat and dry summer rainfall patterns generally benefit Nasturtiums, as they don't like intense heat or overly wet conditions. However, be mindful of slugs, especially during wet springs, and provide adequate drainage to prevent root rot.

Nasturtiums are great companions for many plants in your Pacific Northwest garden. They attract beneficial insects and can even act as a trap crop for aphids, drawing them away from your more prized veggies.

Good companions include tomatoes, cucumbers, and squash, as Nasturtiums can help deter pests that commonly attack these plants. They also work well with broccoli and cabbage, as their strong scent can confuse cabbage moths. Avoid planting them near fennel, as it can inhibit their growth.