Nasturtium in Zone 8A — Pacific Northwest

Nasturtiums are a fantastic addition to any Pacific Northwest garden. Their peppery leaves and vibrant flowers add zest to salads, and the entire plant is edible, even the seed pods! Plus, they're incredibly easy to grow here, offering a big reward for minimal effort.

While our springs can be a bit slow to warm up, and we don't get the intense heat some other regions do, nasturtiums thrive in our mild summers and long, cool falls. With a growing season that stretches over 200 days, you'll have plenty of time to enjoy these beauties.

While nasturtiums prefer to be direct-sown, you *can* start them indoors if you're eager to get a jump start, or you want to ensure earlier blooms. Starting seeds indoors from mid-March through early April gives them a head start before transplanting after the last expected frost.

Use seed trays with a well-draining potting mix. Keep the trays warm and provide plenty of light, especially given our often-overcast spring days. Bottom watering can help prevent damping off and keep the seedlings healthy.

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

Space them 10-12 inches apart to allow for their trailing growth habit. Keep an eye on the weather forecast; a late cold snap can still happen, so be prepared to cover them if needed.

Direct sowing is the preferred method for nasturtiums, as they don't love having their roots disturbed. Sow seeds directly into the garden from mid-April through late August for a continuous supply of blooms and leaves.

Choose a spot with full sun to part shade and prepare the soil by loosening it and removing any weeds. Nasturtiums aren't fussy about soil, but good drainage is key. Sow seeds 10-12 inches apart, about half an inch deep.

Nasturtiums are wonderfully low-maintenance when it comes to watering, making them perfect for our mild, dry summers. In fact, they thrive in slightly poor, dry soil, so resist the urge to overwater. Too much water or fertilizer will result in lush foliage but fewer flowers.

During our wet springs, you likely won't need to water them at all. Once the dry summer months arrive, check the soil moisture with the finger test – if the top two inches are dry, it's time to water. Aim for about an inch of water per week during the driest periods. Water at the base of the plants to avoid wetting the foliage, which can encourage fungal diseases in our sometimes humid conditions.

Signs of underwatering include wilting leaves and stunted growth. Overwatering, on the other hand, can lead to yellowing leaves and root rot. A light layer of mulch can help retain moisture and suppress weeds, but don't overdo it, as nasturtiums prefer drier conditions.

You can expect your first harvest of nasturtium leaves and flowers starting in mid-June and continuing through late October, as long as the weather stays mild. Nasturtiums are ready to harvest once the flowers are fully open and the leaves are a good size.

To harvest, simply snip the flowers or leaves from the plant with scissors or your fingers. Regular harvesting encourages continued production. As our first frost approaches in late October, harvest any remaining flowers and seed pods to preserve their flavor and use them throughout the winter.

Here are some common problems you might encounter with nasturtiums in the Pacific Northwest:

Aphids

• What it looks like: Small, soft-bodied insects clustered on stems and leaves, often accompanied by sticky honeydew.
• What causes it: Aphids are attracted to lush growth, which can be exacerbated by excessive watering or fertilization.
• 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 jet of water or use insecticidal soap if the infestation is severe.

Cabbage Caterpillars

• What it looks like: Green caterpillars munching on leaves, leaving behind ragged holes.
• What causes it: Cabbage white butterflies lay their eggs on nasturtiums, and the caterpillars hatch and feed on the foliage.
• How to fix/prevent it: Handpick caterpillars off the plants or cover them with netting to prevent butterflies from laying eggs. Bacillus thuringiensis (Bt) is an effective organic control.

Black Fly

• What it looks like: Tiny black flies swarming around the plants, particularly in spring.
• What causes it: These flies thrive in damp conditions and can be attracted to overwatered or poorly drained soil.
• How to fix/prevent it: Improve drainage and avoid overwatering. Yellow sticky traps can help catch adult flies.

Pacific Northwest Specific Challenges: Our mild heat and dry-summer conditions are generally favorable for nasturtiums, but slugs can be a problem, especially in the spring. Use slug bait or traps to protect your plants. Also, while late blight is a concern for tomatoes in our region, nasturtiums are not susceptible.

Nasturtiums are excellent companion plants in the Pacific Northwest garden. They attract beneficial insects and can deter pests.

Good companions include tomatoes, cucumbers, and squash, as nasturtiums can help repel aphids and other pests that often plague these plants. They also work well with broccoli and cabbage, helping to deter cabbage white butterflies. Avoid planting nasturtiums near fennel, as they can inhibit each other's growth.