Bluestar
Amsonia tabernaemontana · Apocynaceae
Clusters of pale, steel-blue stars in late spring on a dense, shrubby clump of willow-like leaves that turns clear yellow in autumn.
- Size
- 3 ft tall, 3 ft wide
- Zones
- 3 to 9
- Light
- Full sun to part sun
- Flowers
- Mid May to mid June
- Pets
- No toxicity recorded
- Job in a bed
- Specimen
A bed built around bluestar
The planner designed this bed around bluestar when this page was made: a 12 × 6 ft (3.7 × 1.8 m) naturalistic planting in zone 6, full sun. It chose the other plants from the 966 that suit those conditions, and says below why bluestar stands where it does.
The plants
- 1 Bluestar × 1, blue
- 2 Winter heath × 11, pink
- 3 Coral bells 'Firefly' × 3, red
- 4 Tatarian aster 'Jindai' × 3, purple
- 5 Gray's sedge × 3, green
- 6 Palm sedge × 4, green leaves
- 7 Red spider lily × 5, red
- 8 Spring starflower × 12, white
Why this plant
- The only dense clusters. The others are bells, airy sprays, daisies and others. Shape reads at a distance, where colours blur.
- The only blue.
Why here
- Anchors a back corner. At 3 ft it is one of the taller plants here, and the tallest close the ends of the bed, where they stand in front of nothing.
- A step in the back row. Next to Gray's sedge (2½ ft): no two neighbours there are the same height, so the back steps up and down like a skyline.
- One plant, alone. A feature plant is seen as an object, and needs clear ground around it.
Why now
- In flower for five weeks. From mid May to mid June.
- Fills a gap. For two of those weeks nothing else on the plan is in flower.
Planned as a naturalistic planting: low grasses and groundcovers, the matrix, make up 63% of the planted ground. Tatarian aster 'Jindai' and bluestar anchor the back corners of the bed: the tallest plants on the plan stand there. The scheme leans cool (blue, pink and purple) and uses red for warmth, with green and white to calm things between them.
The planner's own design check: 14 Excellent, 3 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 bluestar goes in a border
At 3 ft it belongs in the middle of a bed. In the planner's ten height classes it is medium tall (2½ to 3 ft).
Its job: specimen. A feature plant with a shape of its own. It stands alone with room around it, and repeats only at a distance.
A three-season plant: blue flowers, a neat green dome all summer, and butter-yellow autumn colour. It takes three years to bulk up and then needs nothing. Cut it back by a third after flowering to keep the dome tight.
- A long-lived, shrub-like perennial for sun or part shade
- Autumn foliage colour
- Native and low-maintenance planting
What to plant with bluestar
Plants recorded as good partners for it, and what each pairing does:
- Peony: in flower together for three weeks, from late May.
- Siberian iris: in flower together for three weeks, from late May.
- Blue false indigo: in flower together for four weeks, from late May; spires rising out of its mound.
Questions about bluestar
Does bluestar need sun or shade?
Bluestar grows in full sun (6 or more hours of direct sun a day) and part sun (4 to 6 hours of sun, including some afternoon sun).
It wants ordinary well-drained soil, of average fertility, and a good soak in dry spells. Once settled in, it stands drought.
What zones does bluestar grow in?
USDA zones 3 to 9. It is hardy to zone 3, which means it survives winter nights down to about −30 °F (−34 °C).
Gardening in Canada? Use the USDA zone for your town: Canada's own zone map uses different numbers.
When does bluestar flower in my zone?
In zone 5 it flowers mid May to mid June. As a spring flower it moves about a week for every zone: earlier where it is warmer, later where it is colder.
| Zone 3 | Late May to late June |
|---|---|
| Zone 4 | Late May to late June |
| Zone 5 | Mid May to mid June |
| Zone 6 | Early May to mid June |
| Zone 7 | Early May to early June |
| Zone 8 | Late April to early June |
| Zone 9 | Mid April to late May |
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 bluestar be planted?
2½ ft (75 cm) apart, from the middle of one plant to the middle of the next. That is a little closer than its full width of 3 ft (90 cm), so a group knits into one patch.
It grows 3 ft (90 cm) tall. Give it the full distance from anything taller, or it will lean out towards the light.
How many bluestar plants do I need?
At 2½ ft apart, set out in staggered rows:
- 2 to fill 10 square feet (about 1 m²)
- 5 for a single row 10 ft (3 m) long
- 6 to fill a 4 × 8 ft bed on its own
In a mixed border, plant it as one, with clear ground around it: a feature plant is seen as an object, and a group of them is a thicket.
In the bed above, the planner used one in one group.
Is bluestar poisonous to dogs and cats?
No toxicity is recorded for dogs, cats, horses or people, according to NC State Extension. Not considered poisonous, but the milky sap can irritate sensitive skin.
"Not toxic" is not "edible": a pet that eats a lot of any plant can be sick.
Do deer eat bluestar?
Mostly not. NC State lists it as resistant to deer. No plant is proof against a hungry deer in a hard winter, but this one is low on the menu.
What flowers after bluestar?
Bluestar is over by mid June. These start as it finishes and carry the same spot on, so it never goes flat:
- Black-eyed Susan: from mid July to mid September, 24 in tall, to stand in front of it and cover its fading stems.
- Butterfly weed: from late June to early August, 24 in tall, to stand in front of it and cover its fading stems.
- Daylily: from late June to early August, 2½ ft tall.
What does bluestar look like in winter?
Bluestar dies down to the ground and there is nothing to see until spring. The old stems can be cut in autumn, or left until spring as shelter for overwintering insects.
Is bluestar good for bees and butterflies?
Bluestar is visited by pollinators and butterflies.
It is native to the United States.
More Amsonia
- Arkansas bluestar Amsonia hubrichtii
- Bluestar 'Blue Ice' Amsonia 'Blue Ice'
- Bluestar 'Storm Cloud' Amsonia tabernaemontana 'Storm Cloud'
In these guides
- Deer-resistant perennials for full sun
- Drought-tolerant perennials for full sun
- Pet-safe plants for a sunny border
- Native perennials for pollinators
- Plants for butterflies
- Plants with blue flowers
Zone guides: Zone 3 · Zone 4 · Zone 5 · Zone 6 · Zone 7 · Zone 8 · Zone 9
Every fact on record
- Type
- Perennial
- Size
- 3 ft (90 cm) tall, 3 ft (90 cm) wide
- Plant
- 2½ ft (75 cm) apart
- Height class
- Medium tall (2½ to 3 ft)
- Place in the bed
- Middle
- Flowers
- Mid May to mid June; dense clusters; blue
- Leaves
- Medium texture, herbaceous; green
- Shape
- Mounding, clumping
- Hardy in
- USDA zones 3 to 9
- Light
- Full sun, part sun
- Soil
- Average, well-drained
- Water
- Moderate
- Feeding
- Light, in spring
- Family
- Apocynaceae
- Comes from
- Central & Eastern U.S.A
- Attracts
- Pollinators, butterflies
- Stands up to
- Deer, drought
Checked against NC State Extension. 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.