Growing borage (Borago officinalis)

Borage is one of those plants that rewards minimal effort with outsized results. The cobalt-blue star-shaped flowers are edible, the young leaves taste of cucumber, and the plant attracts pollinators from first bloom through first frost. I don't grow borage at my Long Island plot -- I rely on.

—- title: "Growing borage (Borago officinalis)" slug: growing-borage hub: vegetables category: "Herb guide" description: "How to grow borage from seed, harvest the edible flowers and leaves, manage self-seeding, and use it as a companion plant. Sourced from Cooperative Extension." date: 2026-06-10 updated: 2026-06-10 author: "Thomas A." reading_time: 9 scientific: "Borago officinalis" zones_min: 2 zones_max: 11 sun: "full sun" —-

Borage is one of those plants that rewards minimal effort with outsized results. The cobalt-blue star-shaped flowers are edible, the young leaves taste of cucumber, and the plant attracts pollinators from first bloom through first frost. I don't grow borage at my Long Island plot — I rely on lavender and catmint for pollinator work there — so this guide draws entirely from Extension sources.

Per NC State Extension, Borago officinalis is a cool-season annual grown primarily for its edible flowers and leaves. It self-seeds prolifically, meaning one planting often becomes a self-sustaining colony.

Identification and species notes

Only one species — Borago officinalis — is commonly cultivated. There is a white-flowered cultivar ('Alba') and a compact form ('Bill Archer'), but the straight species with blue flowers is by far the most common. Per Missouri Botanical Garden, mature plants reach 24-36 inches tall with hollow, branching stems covered in coarse white hairs.

Do not confuse borage with comfrey (Symphytum officinale), which has similar hairy leaves but a perennial habit and different flower structure.

USDA hardiness zones

Per NC State Extension, borage is grown as an annual across USDA zones 2-11. It tolerates light frost as a seedling (down to approximately 28°F), which makes it suitable for early spring sowing in most of the continental United States. In zones 9-11, grow it as a cool-season crop planted in fall for winter and spring harvest.

Light requirements

Per Missouri Botanical Garden, borage performs best in full sun (6 or more hours of direct sun per day). It tolerates partial shade (3-6 hours) but produces fewer flowers and becomes somewhat leggy. In USDA zones 8 and warmer, afternoon shade reduces heat stress during summer.

Sowing and establishment

Borage does not transplant well due to a taproot that resents disturbance. Per Cornell Cooperative Extension, direct sow seeds where the plants are to grow. Sow 1/4 inch deep, 12 inches apart, after the last frost date. Germination occurs in 5-10 days at soil temperatures of 60-70°F.

For succession plantings, sow every 3-4 weeks through early summer. In zones 2-7, the first sowing can go in 2-3 weeks before the last frost date because seedlings tolerate light frost.

Watering

Per Penn State Extension, borage is drought tolerant once established. Water newly seeded areas to maintain even moisture during germination. After establishment, 1 inch of water per week — from rain or irrigation — is sufficient. Overhead watering that wets the foliage can encourage downy mildew, particularly in humid climates; drip irrigation is preferable where the disease is a concern.

Do not overwater. Borage grown in consistently wet soil develops root rot and collapses quickly.

Soil requirements

Per Missouri Botanical Garden, borage thrives in poor to moderately fertile, well-drained soil. It tolerates a wide pH range but performs best between 6.0 and 7.0. Heavily amended, nitrogen-rich soil produces lush foliage at the expense of flowers.

Do not add compost or fertilizer to the planting area unless the soil is extremely depleted. This is one herb that genuinely grows better in lean conditions.

Fertilizing

In average garden soil, borage needs no supplemental fertilizer. If plants are pale and slow to establish, a single application of balanced 10-10-10 fertilizer at the rate recommended on the label is sufficient. Per NC State Extension, excess nitrogen promotes foliage growth and reduces flowering.

Harvesting flowers and leaves

Per Penn State Extension, harvest borage flowers when they are fully open and the anthers are visible. Pick individual flowers by pulling gently from the calyx. The petals are the edible portion; remove the green calyx before using.

Young leaves (from plants under 6 weeks old) are mildest in flavor. Older leaves develop more pronounced cucumber taste and a rougher texture due to the silica-based hairs. Per NC State Extension, leaves can be harvested continuously; remove no more than one-third of the plant's foliage at any harvest.

Managing self-seeding

Borage self-seeds aggressively. A single plant can scatter hundreds of viable seeds. Per Missouri Botanical Garden, to prevent unwanted spread:

• Deadhead spent flowers before seed heads mature and dry
• Pull seedlings from areas where you don't want them while they are small (before the taproot deepens)
• Allow self-seeding in designated areas if you want a self-sustaining colony

Seeds remain viable in the soil for several years, so even thorough deadheading may not eliminate volunteers entirely.

Use as a companion plant

Per Penn State Extension, borage is a documented companion plant for tomatoes and strawberries. The flowers attract beneficial insects including bumblebees and honeybees. There is some evidence that borage deters tomato hornworm, though the mechanism is not fully established in peer-reviewed literature. Plant 12-18 inches from tomato stems to avoid shading.

Pests and diseases

Borage has few serious pest problems. The primary issues, per UC IPM:

Aphids (Myzus persicae and relatives): Heavy infestations on soft new growth. Dislodge with a strong jet of water. insecticidal soap spray (2 tablespoons per gallon) is effective for severe infestations.

Downy mildew (Peronospora boraginacearum): Gray-purple fuzz on leaf undersides, yellow patches on upper surfaces. Favored by cool, humid conditions and poor air circulation. Remove affected leaves; improve spacing to 18 inches between plants; avoid overhead irrigation.

Powdery mildew: White powdery coating on leaves late in the season. Largely cosmetic in annual plants. No treatment necessary unless foliage is being harvested.

Common problems

Frequently asked questions

Is borage safe to eat? Per Penn State Extension, borage flowers and young leaves are edible and have a long history of culinary use. However, borage contains pyrrolizidine alkaloids, which in large quantities can affect liver function. The concentration in culinary quantities is considered negligible, but it is not recommended for consumption in large daily amounts, during pregnancy, or by people with liver disease. Use flowers as a garnish rather than a primary ingredient.

Can borage grow in containers? Per Missouri Botanical Garden, borage can grow in containers 12 inches deep or larger to accommodate the taproot. Use well-draining potting mix. Container-grown plants need more frequent watering — approximately every 2-3 days in summer — and may require a single application of balanced fertilizer at transplant. Expect slightly shorter plants than in-ground specimens.

When should I sow borage to have flowers for a summer event? Per Cornell Cooperative Extension, borage flowers approximately 5-8 weeks after germination. Sow 9-10 weeks before your target date to have plants in full bloom with a small buffer. In zones 5-7, an early May sowing typically yields flowers by late June through August.

Does borage come back every year? Borago officinalis is a true annual. The original plant dies after setting seed. However, per NC State Extension, it self-seeds so reliably that established colonies effectively return each year without replanting, provided some seed heads are allowed to mature.

Recommended gear: Best Insecticidal Soap: How Potassium Salts Kill Soft-Bodied Pests — our buyer's guide covering picks for every budget, ranked by Extension publication consensus and personal use.

Sources

1. NC State Extension — Borago officinalis
2. Missouri Botanical Garden — Borago officinalis
3. Penn State Extension — Herbs
4. Cornell Cooperative Extension — Gardening resources
5. UC IPM — Aphids