Borage in Zone 7B — Northern California

Borage is a fantastic addition to any Northern California garden. Its vibrant blue, star-shaped flowers are not only beautiful, but also attract pollinators like bees – crucial for our Mediterranean climate where we need to support our beneficial insects. Plus, the young leaves have a refreshing cucumber-like flavor, perfect for adding to summer salads or drinks.

Our long growing season in Zone 7B gives you plenty of time to enjoy borage, even with the occasional drought or early heat wave we sometimes experience. With careful planning and water-wise gardening practices, you can easily grow borage from mid-March through early September, enjoying its blooms and flavor for months.

You can transplant borage seedlings outdoors in early to late March, giving them a head start before the summer heat. Before you put them in the ground, be sure to harden them off by gradually exposing them to outdoor conditions for about a week. This helps them adjust to the sun and wind.

Space your borage plants about 12-18 inches apart to allow for adequate growth. Keep an eye on the weather forecast, as we can still get some late frosts in early spring. If frost is predicted, cover your young plants with horticultural fleece or blankets.

Direct sowing is the preferred and easiest method for growing borage in Northern California. Sow seeds mid-March through early September, ensuring the soil temperature is at least 60°F for optimal germination. Borage is easy to direct sow and readily self-seeds, so be prepared to manage volunteer seedlings in future seasons!

Prepare the soil by loosening it and adding compost to improve drainage and fertility. Sow seeds about ½ inch deep and 12-18 inches apart. Keep the soil consistently moist until the seedlings emerge, usually within a week or two.

Borage needs moderate watering, especially during our dry summers in Northern California. While relatively easy-going, it’s not truly drought-tolerant and will suffer without enough moisture.

During the cooler spring and fall months, water deeply about once a week, providing about an inch of water. In the heat of summer, increase watering to two or three times a week, ensuring the soil stays consistently moist but not waterlogged. Use the finger test: stick your finger about two inches into the soil – if it feels dry, it's time to water. Focus on watering at the base of the plant to avoid wetting the foliage, which can encourage powdery mildew in our microclimates.

Signs of underwatering include wilting leaves and stunted growth. Overwatering can lead to yellowing leaves and root rot. A layer of mulch around the base of the plants will help retain moisture in the soil and reduce the need for frequent watering, which is especially important during our water restrictions.

You can expect your first borage harvest from early May through late November, about 55 days after sowing. Look for fully open, star-shaped blue flowers to harvest – these are the most flavorful. The young leaves are also edible and have a refreshing cucumber taste.

To harvest, gently snip off the flowers or leaves with scissors or pruners, being careful not to damage the rest of the plant. Regular harvesting encourages continuous production of flowers and leaves.

As our first frosts approach in mid- November, you can try to extend the harvest by covering the plants with horticultural fleece on colder nights. However, borage is an annual, so it will eventually die back with the frost. Let some of the last flowers go to seed if you want them to self-sow for the following year.

Here are some common problems you might encounter growing borage in Northern California:

Self-seeding aggressively

• What it looks like: Numerous borage seedlings popping up throughout your garden, even in unwanted areas.
• What causes it: Borage readily self-seeds, especially in our mild winters and long growing season.
• How to fix/prevent it: Deadhead flowers before they go to seed. Pull out unwanted seedlings as soon as you see them. Consider growing borage in containers to limit its spread.

Powdery mildew

• What it looks like: White or grayish powdery coating on leaves, stems, and sometimes flower buds. Leaves curl, yellow, and die.
• What causes it: Various fungi that thrive in warm days, cool nights, and moderate humidity, which we sometimes experience in our microclimates, especially near the coast. Dry leaf surfaces actually favor it.
• How to fix/prevent it: Improve air circulation by spacing plants properly and pruning overcrowded foliage. Remove affected leaves promptly. Neem oil or potassium bicarbonate sprays can help. A milk spray (1 part milk to 9 parts water) is also surprisingly effective.

Can become leggy

• What it looks like: Long, weak stems with sparse foliage and fewer flowers.
• What causes it: Insufficient sunlight or overly rich soil can cause borage to become leggy.
• How to fix/prevent it: Ensure borage receives at least 6 hours of sunlight per day. Avoid over-fertilizing. Pinch back the tips of the stems to encourage bushier growth.

Northern California Specific Challenges: Our moderate-to-hot summers and dry-summer rainfall can stress borage if it's not watered adequately. The low humidity generally helps prevent fungal diseases, but powdery mildew can still be an issue in certain microclimates. Be mindful of water restrictions and use water-wise gardening practices to keep your borage healthy and productive.

Borage is a great companion plant for many crops in the Northern California garden. It attracts pollinators to your tomatoes, squash, strawberries, and cucumbers, improving fruit set. It's also said to deter pests like tomato hornworms and cabbage moths.

There aren't any truly bad companions for borage, but avoid planting it too close to other plants that require very dry soil, as borage prefers moderate moisture. Keep in mind borage can self-seed readily, so avoid planting it near delicate or easily crowded plants.