Bottle gentian
Gentiana andrewsii ·
Clusters of deep blue flowers that never open, like fat buds, at the top of leafy stems in early autumn. Only bumblebees are strong enough to push inside.
- Size
- 20 in tall, 16 in wide
- Zones
- 3 to 7
- Light
- Full sun to part shade
- Flowers
- Late August to early October
- Pets
- Not checked
- Job in a bed
- Drift
A bed built around bottle gentian
The planner designed this bed around bottle gentian when this page was made: a 12 × 6 ft (3.7 × 1.8 m) English border in zone 6, part sun. It chose the other plants from the 708 that suit those conditions, and says below why bottle gentian stands where it does.
The plants
- 1 Bottle gentian × 8, blue
- 2 Moor grass 'Greenlee' × 11, tan
- 3 Coral bells 'Firefly' × 5, red
- 4 Brown-eyed Susan × 3, yellow
- 5 Foxglove beardtongue × 3, white
- 6 Inkberry 'Gem Box' × 1, dark green leaves
- 7 Daffodil × 10, orange
Why this plant
- The only dense clusters. The others are spires, airy sprays, daisies and others. Shape reads at a distance, where colours blur.
- The only blue. The one cool colour: every other flower here is hot or neutral.
Why here
- In the middle. At 20 in it is the step between moor grass 'Greenlee' (12 in) in front and foxglove beardtongue (3½ ft) behind: each is seen over the one before.
- A step in the back row. Next to inkberry 'Gem Box' (2½ ft) and brown-eyed Susan (4 ft): no two neighbours there are the same height, so the back steps up and down like a skyline.
- 8 plants in 2 groups (5 and 3). Seen again further along, the same plant ties the bed together.
Why now
- In flower for six weeks. From late August to early October.
- In company. With brown-eyed Susan in late August: 2 kinds at once.
Planned as an English border: 5 of the 7 groups (71%) are drifts, longer along the bed than they are deep. The bed is balanced: the left half carries 52% of the visual weight and the right half 48%. There is more moor grass 'Greenlee' than anything else, 11 plants in all.
The planner's own design check: 11 Excellent, 6 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 bottle gentian goes in a border
At 20 in it belongs in the middle of a bed. In the planner's ten height classes it is medium short (18 to 24 in).
Its job: drift. Planted in a small group of three or five, and repeated further along in the other number.
The truest blue of autumn. It is slow and resents disturbance, so plant it young in moist soil and leave it. Good beside the red of cardinal flower.
- Autumn blue for moist soil
- Rain gardens and stream sides
- Native woodland edges
What to plant with bottle gentian
Plants recorded as good partners for it, and what each pairing does:
- Cardinal flower: in flower together for three weeks, from late August; tall enough (3½ ft) to stand behind it.
- Great blue lobelia: in flower together for four weeks, from late August; tall enough (2½ ft) to stand behind it; happy in the same moist soil.
- Turtlehead 'Hot Lips': in flower together for five weeks, from late August; tall enough (3 ft) to stand behind it; happy in the same moist soil.
Questions about bottle gentian
Does bottle gentian need sun or shade?
Bottle gentian grows in full sun (6 or more hours of direct sun a day), part sun (4 to 6 hours of sun, including some afternoon sun) and part shade (2 to 4 hours of sun, mostly in the morning).
It wants soil that stays evenly moist, rich in organic matter, and a good soak in dry spells.
What zones does bottle gentian grow in?
USDA zones 3 to 7. It is hardy to zone 3, which means it survives winter nights down to about −30 °F (−34 °C).
Above zone 7 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 bottle gentian flower in my zone?
In zone 5 it flowers late August to early October. As a summer flower it moves about half a week for every zone: earlier where it is warmer.
| Zone 3 | Early September to early October |
|---|---|
| Zone 4 | Early September to early October |
| Zone 5 | Late August to early October |
| Zone 6 | Late August to early October |
| Zone 7 | Late August to early October |
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 bottle gentian be planted?
12 in (30 cm) apart, from the middle of one plant to the middle of the next. That is a little closer than its full width of 16 in (40 cm), so a group knits into one patch.
It grows 20 in (50 cm) tall. Give it the full distance from anything taller, or it will lean out towards the light.
How many bottle gentian 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 a group of three or five, with a second group further along in the other number.
In the bed above, the planner used eight in two groups.
What flowers after bottle gentian?
Bottle gentian is over by early October. These start as it finishes and carry the same spot on, so it never goes flat:
- Japanese onion 'Ozawa': from early October to early November, 10 in tall, to stand in front of it and cover its fading stems.
- Chrysanthemum 'Sheffield Pink': from late September to early November, 2½ ft tall.
- Tatarian aster 'Jindai': from early October to early November, 4 ft tall.
What does bottle gentian look like in winter?
Bottle gentian 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.
More Gentiana
- Crested gentian Gentiana septemfida
- Stemless gentian Gentiana acaulis
- Willow gentian Gentiana asclepiadea
In these guides
Every fact on record
- Type
- Perennial
- Size
- 20 in (50 cm) tall, 16 in (40 cm) wide
- Plant
- 12 in (30 cm) apart
- Height class
- Medium short (18 to 24 in)
- Place in the bed
- Middle
- Flowers
- Late August to early October; dense clusters; blue
- Leaves
- Medium texture, herbaceous; dark green
- Shape
- Upright, clumping
- Hardy in
- USDA zones 3 to 7
- Light
- Full sun, part sun, part shade
- Soil
- Rich, evenly moist
- Water
- Moderate
- Feeding
- Light, in spring
Checked against 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.