Students for Stewardship The Cork Board
← Back to the library

Common Flax

Linum usitatissimum (LY-num yoo-sit-ah-TIS-sih-mum)

Family: Linaceae Non-native Shrub

Common flax is an flowering, short-lived, annual subshrub in the flax family and a native of Turkey and Iran. In its native habitat, it can be grown as a perennial, but it is not cold tolerant and is more typically grown as an annual. It produces pale blue flowers on slender, but strong, stems in late spring into mid-summer. The thin, wiry stems that support the flower buds appear delicate, but are difficult to break. Common flax prefers moist, well-drained, mildly acid, neutral and mildly alkaline soils. It does best in full sun and cannot grow in the shade. The plant tolerates strong winds but not maritime exposure. It will tolerate drought and dry or rocky soil, but clay soils can cause the plant to root shallowly that will cause problems for the plant in cold weather. After perennial flax finishes flowering in summer, prune back the stems by half to prevent the plants from becoming leggy and sparse. Pruning halfway through the bloom season will extend flowering. Division is not advisable, because the roots system is sparse, but you can propagate with seed or stem cuttings in summer. Flax was first known to be used as a textile 30,000 years ago. Today, common flax plants are commercially grown for making linen (from the stems) and linseed oil (from the seeds) . Diseases, Insect Pests, and Other Plant Problems: Cutworms and grasshoppers can be occasional pests.

Source: NC State Extension Gardener Plant Toolbox ↗ NC State Extension Gardener Plant Toolbox, 65 attributes.

How it fits the guild

Guild layer 3 - Shrub Optimal soil pH Acid (<6.0); Alkaline (>8.0); Neutral (6.0-8.0)
See companions & conflicts ↓

Companions & Conflicts

Curated pairwise relationships between this plant and others in the library — who feeds whom, who competes, who confuses the pests. Green reads as a good pairing, red as one to avoid.

No curated interactions recorded for this species yet.

Also noted by NC State

Related species the NC State Plant Toolbox flags for this plant — look-alikes to tell apart, and plants that play a similar role in a planting. Ones we carry in the library are linked.

Full plant profile

Growing Conditions
Plant type
Annual; Poisonous; Shrub
Life cycle
Annual
USDA zones
4a, 4b, 5a, 5b, 6a, 6b, 7a, 7b, 8a, 8b
Light
Full sun (6 or more hours of direct sunlight a day) | Partial Shade (Direct sunlight only part of the day, 2-6 hours)
Soil texture
High Organic Matter; Loam (Silt); Shallow Rocky
Soil pH
Acid (<6.0); Alkaline (>8.0); Neutral (6.0-8.0)
Soil drainage
Good Drainage | Moist | Occasionally Dry
Available space
12 inches-3 feet
NC region
Coastal; Mountains; Piedmont
Growth rate
Medium
Maintenance
Medium
Canopy layer
3 - Shrub
Form & Appearance
Habit / form
Creeping; Erect; Multi-stemmed
Foliage
Semi-evergreen
Leaf color
Green
Leaf type
Simple
Leaf arrangement
Alternate
Leaf shape
Lanceolate
Leaf margin
Entire
Leaf feel
Smooth
Leaf size
1-3 inches long, < 1 inch wide
Hairs present
No
Leaf detail
Leaves are simple, alternate, narrow, with smooth margins.
Flower color
Blue
Flower value
Showy
Flower form
Cyme
Flower shape
Wheel
Flower size
< 1 inch
Flower detail
Pale blue and 5-parted, the petals of the 1 inch flowers are broad and spreading.
Bloom time
Spring; Summer
Fruit color
Brown/Copper
Fruit type
Capsule
Fruit detail
Globoid seed capsule containing 10 cells (5 fertile cells and 5 sterile cells) and 10 flattened seeds.
Stem color
Blue; Green
Stem detail
One or more unbranched stems rise up from the base of the plant. These flowering stems may be erect, or they can sprawl across the ground.
Wildlife & Ecology
Native status
Non-native
Origin
Turkey south to Iran
Distribution
Naturalized throughout Europe, western and central North America
Food & Medicine
Harvest time
Fall
Fruit type
Capsule

Uses (ethnobotany)

Linen is made from the stems and linseed oil from the seeds.

Landscape Use
Landscape location
Meadow; Naturalized Area
Landscape theme
Cottage Garden; Rock Garden
Design feature
Border; Mass Planting
Garden tags
#poisonous #perennial #morning sun #subshrub #wildflower #annual #summer flowers #blue flowers #spring interest #full sun tolerant #bushy #flowering #well-drained soil #fiber plant #short lived #partial shade tolerant
Problems & Resistance
Insect problems
Caterpillars Found on Flowers and Foliage
Other problems
Cottontail Rabbit
Problems
Contact Dermatitis; Poisonous to Humans; Weedy
Resistant to
Drought; Dry Soil; Poor Soil
Propagation
Seed; Stem Cutting
Poison severity
Medium
Poison parts
Bark; Flowers; Fruits; Leaves; Roots; Sap/Juice; Seeds; Stems
Poison symptoms
TOXIC ONLY IF LARGE QUANTITIES EATEN. SKIN IRRITATION MINOR, OR LASTING ONLY FOR A FEW MINUTES. Linseed oil may cause skin irritation upon contact. Ingestion causes difficulty of breathing, paralysis, and convulsions.
Toxic principle
Cyanogenic glycoside (linamarin)
Contact dermatitis
Yes
Toxicity summary
Medium severity poison; parts: Bark; Flowers; Fruits; Leaves; Roots; Sap/Juice; Seeds; Stems; contact dermatitis

Planted at Hunnicutt

Nobody’s planted this one yet.