How to Grow Borage | Complete Growing Guide

At a Glance

Quick Facts

Factor	Value
Drainage	well-drained; tolerates chalk, clay, loam, and sand

Soil & Growing Conditions

Water: does best in dry, sunny places once established; tolerates poor/dry soil

Growth Stages

Stage	BBCH	Notes
Sowing and germination	0	Sow in April in seed trays or pots at about 15C, or direct sow outdoors in spring; germination takes roughly five to ten days (RHS).
Establishment and spacing	1	Space plants about 50cm apart in full sun or light shade, on any soil that is not waterlogged (RHS).
Vegetative growth	3	Plants grow into an erect habit 50-70cm tall; keep soil moist through summer for the biggest, best plants (RHS).
Flowering and harvest	6	Flowers appear about 10-12 weeks after a spring sowing; pick individual blooms just as they open. Watch for powdery mildew later in summer once peak flowering is over (RHS).

Harvest & Storage

When to pick: Pick blossoms as they open; use leaves fresh, picking young/tender leaves for best flavour (they are seldom dried). Successive sowings at 4-week intervals extend the harvest.

Diseases

Powdery mildew

RHS: "May be susceptible to powdery mildews."

Pests

Slugs

Gastropoda (slugs, various spp.)

RHS: "Foliage may be damaged by slugs and leaf-mining flies."

Companion Planting

Strawberry

beneficial

Fragaria x ananassa

Pollinator attraction

Borage, the Bee-Magnet Herb with Starry Blue Flowers

Starry blue flowers

Bright blue, star-shaped flowers about 2cm across appear over a long period through summer.

Buds open in succession

Hairy, nodding buds open in succession, keeping the plant in flower for weeks on end.

An erect annual herb

RHS: borage forms an erect plant 50-70cm tall, thriving in full sun on any soil that is not waterlogged.

Cucumber-scented leaves

The broad, bristly leaves carry a distinct cucumber scent and are picked young for salads.

Coarsely hairy throughout

Stems and foliage are covered in coarse white hairs, a hallmark of the borage family.

References

1. Ecological Entomology (Wiley) -- Griffiths-Lee, Nicholls & Goulson, 2020 - Companion planting to attract pollinators increases the yield and quality of strawberry fruit in gardens and allotments

   Peer-reviewed; abstract fetched directly by research subagent from University of Sussex repository. Researcher-led trial + UK-wide citizen-science replication.

2. GBIF - GBIF Backbone Taxonomy match: Borago officinalis (family/genus/species)

   country=INTL

3. Royal Horticultural Society - Borago officinalis | borage

   country=UK

4. Royal Horticultural Society - How to grow borage

   Sow in seed trays and pots in April at 15C, or direct sow in spring. Space plants about 50cm apart. Thrives in full sun but tolerates light shade; grows on any soil that is not waterlogged, preferring moist soil in summer for the biggest plants. Annual borage reaches 50-70cm tall with an erect habit. Self-seeds readily; seedlings germinating later in summer usually flower but stay shorter. Can get powdery mildew later in summer, after peak flowering.

5. University of Maryland Extension - Borage

   country=US

6. University of Minnesota Extension (Nathan Hecht, Minnesota Fruit Research) - Berries, bees, and borage

   Fetched by research subagent; 2016-2018 field trials.

6 independent sources are cited for this crop. Where they disagree - soil pH is the clearest case - every figure is preserved rather than averaged into false precision.