Nasturtium in Zone 8B — Northern California

Nasturtiums are a fantastic addition to any Northern California garden. Their peppery leaves and vibrant flowers add a unique flavor to salads, and the entire plant is edible! Plus, they attract beneficial insects while acting as a trap crop for pests, making them a worthwhile addition to your vegetable beds.

Our Mediterranean climate, with its long growing season, is ideal for nasturtiums. While we face challenges like drought and water restrictions, nasturtiums are surprisingly drought-tolerant and thrive with minimal intervention. With a growing season that stretches for about 269 days, you'll have plenty of time to enjoy these beauties.

While nasturtiums prefer direct sowing, you *can* start them indoors if you're eager to get a head start. Start your seeds indoors from early to late February, about four weeks before you plan to transplant them. Use seed trays with good drainage and provide warmth and light.

Bottom watering is helpful to prevent damping off. Since our springs here in Northern California can have a bit of early warmth followed by cooler spells, starting indoors can give you a bit of a buffer, but honestly, direct sowing is usually the way to go.

Transplant your nasturtium seedlings outdoors from early March through early April. Before transplanting, harden them off by gradually exposing them to outdoor conditions for about a week. This will help them adjust to the sun and temperature fluctuations.

Space the seedlings 10-12 inches apart to give them room to spread. Keep an eye on the weather forecast; a late frost can still happen, so be prepared to cover your young plants if necessary.

Direct sowing is the preferred method for nasturtiums, as they don't love having their roots disturbed. Sow seeds directly into the garden from early March through mid September. This long window takes advantage of our extended growing season.

Choose a spot with full sun to partial shade and prepare the soil by loosening it and removing any weeds. Nasturtiums aren't picky about soil, so don't worry about amending it too much. Plant the seeds about half an inch deep, spacing them 10-12 inches apart. Keep the soil consistently moist until the seedlings emerge.

Nasturtiums are wonderfully drought-tolerant, making them perfect for water-wise gardening in Northern California. They thrive in poor, dry soil, and too much water or fertilizer can actually lead to more leaves than flowers. Remember, less is more with these plants.

During our dry summers, water deeply but infrequently. A good rule of thumb is to check the soil about two inches deep – if it's dry, it's time to water. Aim for about 1 inch of water per week, focusing on watering at the base of the plant to avoid wetting the foliage. Given our low humidity, overhead watering isn't as risky as in other regions, but watering at the base is still preferable.

If the leaves start to wilt or turn yellow, you might be underwatering. On the other hand, if the leaves are consistently yellowing and the soil is soggy, you're likely overwatering. A layer of mulch around the base of the plants can help retain moisture and suppress weeds, which is especially helpful during our hotter months.

You can expect your first harvest of nasturtium flowers and leaves from early May through late November. Given our long growing season, that's a pretty great window. Nasturtiums are ready to harvest about 55 days after planting.

Harvest the flowers when they are fully open for the best flavor and visual appeal. For the leaves, snip them off as needed. Don't forget the seed pods! Harvest them when they are green and plump to make caper-like pickles. Regular harvesting encourages continued production of both flowers and leaves.

As our first frost approaches in late November, harvest any remaining flowers and seed pods. The plants will likely die back with the frost, but you can collect seeds for next year's planting.

Even though nasturtiums are fairly easy to grow, you might encounter a few common problems in Northern California. The top three issues are aphids, cabbage caterpillars, and black fly.

Aphids *What it looks like:* Clusters of small, soft-bodied insects, usually green, on stems and undersides of leaves. Leaves may be sticky or distorted. *What causes it:* Aphids thrive in warm, dry conditions, which we often experience in the spring and summer. They are attracted to stressed plants. *How to fix/prevent it:* Nasturtiums are often used as a trap crop for aphids, drawing them away from other plants. If infestations get too heavy, spray with a strong jet of water or insecticidal soap. Encourage beneficial insects like ladybugs.

Cabbage Caterpillars *What it looks like:* Holes in leaves, especially on younger plants. You might see green caterpillars feeding on the leaves. *What causes it:* Cabbage white butterflies lay their eggs on the leaves, and the caterpillars hatch and start feeding. *How to fix/prevent it:* Handpick caterpillars off the plants. Use row covers to prevent butterflies from laying eggs. Bacillus thuringiensis (Bt) is an effective organic treatment.

Black Fly *What it looks like:* Similar to aphids, these small black flies cluster on new growth and suck sap. *What causes it:* Like aphids, black fly prefer warm and relatively dry conditions. *How to fix/prevent it:* A strong spray of water can dislodge them. Insecticidal soap is also effective. Ensure good air circulation around plants.

Northern California Specific Challenges: Our moderate-to-hot summers and dry-summer rainfall can stress nasturtiums if not managed properly. Providing adequate but not excessive water and ensuring good air circulation can help prevent many of these problems. Keep an eye out for pests that thrive in these conditions and take action early.

Nasturtiums are excellent companion plants in the Northern California garden! They attract beneficial insects and can even act as a trap crop for pests, protecting other vegetables.

Good companions include tomatoes, cucumbers, and squash. Nasturtiums deter pests that can harm these crops. They also grow well with broccoli and cabbage, helping to keep cabbage white butterflies away. Avoid planting nasturtiums near fennel, as they can inhibit each other's growth.