Blue flax
Linum perenne · Linaceae
Sky-blue flowers open each morning and drop by afternoon, on wiry, arching stems with needle-like leaves. New flowers come every day for two months.
- Size
- 18 in tall, 12 in wide
- Zones
- 5 to 8
- Light
- Full sun
- Flowers
- Mid May to mid July
- Pets
- No toxicity recorded
- Job in a bed
- Weaver
A bed built around blue flax
The planner designed this bed around blue flax when this page was made: a 12 × 6 ft (3.7 × 1.8 m) cottage garden in zone 6, full sun. It chose the other plants from the 715 that suit those conditions and its dry soil, and says below why blue flax stands where it does.
The plants
- 1 Blue flax × 4, blue
- 2 Heath aster 'Snow Flurry' × 3, white
- 3 Lemon thyme × 5, pink
- 4 False sunflower 'Summer Sun' × 3, yellow
- 5 Carolina lupine × 4, yellow
- 6 Silver sage × 1, silver leaves
- 7 Ornamental onion 'Purple Sensation' × 4, purple
- 8 Spring starflower × 12, blue
Why this plant
- The only open bowls. The others are daisies, dense clusters, spires and others. Shape reads at a distance, where colours blur.
Why here
- In the middle. At 18 in it is the step between silver sage (12 in) in front and false sunflower 'Summer Sun' (3½ ft) behind: each is seen over the one before.
- A step in the back row. Next to ornamental onion 'Purple Sensation' (2½ ft) and Carolina lupine (4 ft): no two neighbours there are the same height, so the back steps up and down like a skyline.
- 4 plants in 4 places. An accent is a punctuation mark: the repeat along the bed gives it rhythm.
Why now
- In flower for 9 weeks. From mid May to mid July.
- Fills a gap. For one of those weeks nothing else on the plan is in flower.
Planned as a cottage garden: 20 of the 20 plants (100%), bulbs aside, stand alone or in groups of no more than five, small enough for the kinds to mingle. The bold leaves of silver sage are set against the fine leaves of blue flax, the kind of contrast that keeps a bed from blurring. Lemon thyme carries the bed through winter.
The planner's own design check: 13 Excellent, 4 Good. It flags one thing to watch: Nothing on this plan is highly poisonous or an aggressive spreader.
Open this bed in the planner Change its size, the sun or the style, move plants about, or swap one for another.
Where blue flax goes in a border
At 18 in it belongs at the front of a bed. In the planner's ten height classes it is short (12 to 18 in). It is airy enough to see through, so it can also come forward and veil what is behind it.
Its job: weaver. A light, airy plant threaded singly between sturdier ones to knit the planting together.
A true sky blue is rare, and this is one of the purest. The plant is thin and airy, so scatter it among other plants. It is at its best before noon.
- Clear blue for dry, sunny beds
- Meadow and gravel gardens
- Threading through other plants
What to plant with blue flax
Plants recorded as good partners for it, and what each pairing does:
- Cheddar pinks 'Firewitch': in flower together for six weeks, from mid May; low enough (8 in) to stand in front of it; happy in the same dry soil.
- Blue fescue: its blue-green leaves are a setting for the flowers, before and after; low enough (10 in) to stand in front of it; happy in the same dry soil.
- Yarrow 'Moonshine': blue against yellow, opposite each other on the colour wheel, in flower together for five weeks; happy in the same dry soil.
Questions about blue flax
Does blue flax need sun or shade?
Blue flax grows in full sun (6 or more hours of direct sun a day).
It wants dry, sharply drained soil, on the lean side, with no feeding, and little watering once settled. Once settled in, it stands drought.
What zones does blue flax grow in?
USDA zones 5 to 8. It is hardy to zone 5, which means it survives winter nights down to about −10 °F (−23 °C).
Above zone 8 it struggles: the zones measure winter cold, but a plant's top zone usually means the summers are too hot or the winters too mild for it to rest.
Gardening in Canada? Use the USDA zone for your town: Canada's own zone map uses different numbers.
When does blue flax flower in my zone?
In zone 5 it flowers mid May to mid July. As a spring flower it moves about a week for every zone: earlier where it is warmer, later where it is colder.
| Zone 5 | Mid May to mid July |
|---|---|
| Zone 6 | Early May to mid July |
| Zone 7 | Early May to early July |
| Zone 8 | Late April to early July |
Worked out from Hopkins' bioclimatic law: spring arrives about four days later for each degree of latitude north, and one zone is roughly two degrees. A warm spring or a cold one moves any garden two weeks either way.
How far apart should blue flax be planted?
12 in (30 cm) apart, from the middle of one plant to the middle of the next. That is about its full width, so each plant keeps its own outline.
It grows 18 in (45 cm) tall. Give it the full distance from anything taller, or it will lean out towards the light.
How many blue flax plants do I need?
At 12 in apart, set out in staggered rows:
- 12 to fill 10 square feet (about 1 m²)
- 11 for a single row 10 ft (3 m) long
- 38 to fill a 4 × 8 ft bed on its own
In a mixed border, plant it as one at a time, threaded between sturdier plants.
In the bed above, the planner used four in four groups.
Is blue flax poisonous to dogs and cats?
No toxicity is recorded for dogs, cats, horses or people, according to NC State Extension.
"Not toxic" is not "edible": a pet that eats a lot of any plant can be sick.
Is there a native plant like blue flax?
Blue flax comes from Europe and Asia. These North American natives come closest to doing its job:
- Rocky Mountain columbine: the same job in a bed and the same colour; belongs in the middle, not at the front, 6 in taller.
- Harebell: the same job in a bed and the same colour; 6 in shorter, 4 in narrower.
- Mexican hat: the same job in a bed; belongs in the middle, not at the front, 6 in taller.
Matched the way the planner's Swap button matches plants: the same job in a bed, then size, then flowering time.
Do deer eat blue flax?
They may. NC State does not list it as resistant to deer or rabbits. Where they visit, protect it, or plant it among ones they avoid.
Will blue flax spread?
It seeds itself about; the risk of it taking over is moderate. Short-lived, but keeps going by self-seeding. Thin or move seedlings where they are not wanted.
What flowers after blue flax?
Blue flax is over by mid July. These start as it finishes and carry the same spot on, so it never goes flat:
- Lilyturf: from early August to mid September, 16 in tall.
- Black-eyed Susan: from mid July to mid September, 24 in tall.
- Ornamental onion 'Millenium': from mid July to late August, 18 in tall.
What does blue flax look like in winter?
Blue flax holds some of its leaves into winter, more in a mild year or a sheltered spot, and they look tired by March. Cut the old ones off as new growth starts.
In these guides
Every fact on record
- Type
- Perennial
- Size
- 18 in (45 cm) tall, 12 in (30 cm) wide
- Plant
- 12 in (30 cm) apart
- Height class
- Short (12 to 18 in)
- Place in the bed
- Front, or further forward: it is airy enough to see through
- Flowers
- Mid May to mid July; open bowls; blue
- Leaves
- Fine texture, semi-evergreen; blue-green
- Shape
- Upright, self-seeding
- Hardy in
- USDA zones 5 to 8
- Light
- Full sun
- Soil
- Lean, dry and sharply drained
- Water
- Low
- Feeding
- None needed
- Family
- Linaceae
- Comes from
- Europe and Asia
- Stands up to
- Drought, poor soil
Checked against NC State Extension and VASCAN (plants of Canada). Flowering times are for zone 5: later in colder zones, earlier in warmer ones. Toxicity and spread information is a general gardening guide, not veterinary or medical advice, and invasive status varies by region. If a person or pet eats a plant, contact poison control or a vet. Check your local invasive species list before planting anything with a spread warning.