Nasturtium in Zone 8B — Southern California

Nasturtiums are a fantastic addition to any Southern California garden. Their peppery flowers and leaves add a unique zest to salads, and they're surprisingly easy to grow in our mild climate. Plus, they attract beneficial insects while looking beautiful – a win-win for any SoCal gardener aiming for a year-round harvest.

While we face challenges like drought and summer heat inland, nasturtiums are surprisingly resilient. Our long growing season, nearly 300 days, gives you plenty of time to enjoy these vibrant plants. With the right timing, you can have nasturtiums thriving in your garden almost year-round.

Starting nasturtiums indoors isn't essential in our climate, but it can give you a head start, especially if you want blooms extra early. If you're considering it, begin around mid-January through early February, about four weeks before you plan to transplant.

Use seed trays with a good seed-starting mix. Keep them in a warm spot with plenty of light – a sunny windowsill or under grow lights works well. Water from the bottom to encourage strong root growth – just set the tray in a shallow dish of water until the soil surface is moist. With our very-early spring, starting indoors gives you a jump on the season.

Transplanting nasturtiums is best done in late February through late March, once the danger of frost has passed. Before planting them in their final spot, harden them off by gradually exposing them to outdoor conditions for about a week.

Choose a sunny or partially shaded spot and space them about 10-12 inches apart. Keep an eye on the weather forecast – even though our winters are mild, a late cold snap can still happen.

Direct sowing is the preferred method for nasturtiums, as they don't love having their roots disturbed. You can direct sow from late February through early October, giving you a long window of opportunity in our SoCal climate.

Choose a spot with well-draining soil, and make sure the soil temperature is at least 65°F. Plant the seeds about half an inch deep, spacing them 10-12 inches apart. Water gently after planting, and keep the soil consistently moist until they germinate.

Nasturtiums are surprisingly drought-tolerant, making them a great choice for our water-wise Southern California gardens. They actually thrive in slightly poor, dry soil, and too much water can lead to more leaves than flowers. Remember, less is often more with these plants.

During our winter-wet season, you might not need to water them at all unless we're experiencing an unusually dry spell. In the hotter summer months, check the soil moisture about two inches deep – the "finger test." If it feels dry, give them a good soak, aiming for about 1 inch of water per week, depending on rainfall.

Water at the base of the plants to avoid wetting the foliage, which can encourage fungal diseases in our low-to-moderate humidity. If the leaves start to droop, they're likely thirsty. Yellowing leaves can indicate overwatering. Adding a layer of mulch, like wood chips, can help retain moisture in the soil and keep the roots cool during our hot summers.

You can expect your first nasturtium harvest around mid-April through early December, about 55 days after planting. Both the flowers and leaves are edible, so keep an eye out for fully open blooms – they're the most flavorful. The seed pods can also be harvested and pickled for a caper-like treat.

To harvest, simply snip the flowers or leaves with scissors or your fingers. Be gentle to avoid damaging the plant, and it will continue to produce more. Even as our first frost approaches in early December, you can often still get a few more harvests if you protect the plants from any unexpected cold snaps.

Here are some common issues you might encounter with nasturtiums in Southern California:

Aphids *What it looks like:* Clusters of tiny green, black, or brown bugs on stems and leaves. Leaves may be sticky or distorted. *What causes it:* Aphids are attracted to stressed plants. Our dry climate and occasional Santa Ana winds can stress plants, making them more vulnerable. *How to fix/prevent it:* Nasturtiums are actually great 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 introduce beneficial insects like ladybugs.

Cabbage Caterpillars *What it looks like:* Holes in the leaves, often with green or brown caterpillars present. *What causes it:* Cabbage white butterflies lay their eggs on nasturtiums, and the caterpillars hatch and start munching. *How to fix/prevent it:* Handpick the caterpillars off the plants. You can also use row covers to prevent the butterflies from laying eggs.

Black Fly *What it looks like:* Similar to aphids, these small black flies will congregate on new growth and suck the sap from the plant. *What causes it:* Black fly thrive in warm weather. *How to fix/prevent it:* A strong blast of water from a hose can dislodge black flies. Insecticidal soap can also be effective.

Southern California Specific Challenges: Our hot summers inland can sometimes stress nasturtiums, even though they're drought-tolerant. Providing some afternoon shade during the hottest months can help. The winter-wet season can also lead to fungal diseases if the soil is not well-draining.

Nasturtiums are great companions for many plants in your Southern California garden. They attract beneficial insects and can even act as a trap crop for aphids.

Good companions include:

• Tomatoes: Nasturtiums can help repel tomato hornworms.
• Cucumbers: They help deter cucumber beetles.
• Squash: They help deter squash bugs.
• Broccoli and Cabbage: They attract beneficial insects that prey on cabbage worms.

Avoid planting nasturtiums near fennel, as they can inhibit each other's growth.