Willow gentian
Gentiana asclepiadea ·
Arching stems lined with pairs of willow-like leaves, and at every pair a deep blue trumpet, in late summer and early autumn.
- Size
- 2½ ft tall, 24 in wide
- Zones
- 5 to 7
- Light
- Part sun to part shade
- Flowers
- Early August to mid September
- Pets
- Not checked
- Job in a bed
- Drift
A bed built around willow gentian
The planner designed this bed around willow 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 willow gentian stands where it does.
The plants
- 1 Willow gentian × 3, blue
- 2 Mouse-ear coreopsis 'Nana' × 26, yellow
- 3 Creeping mahonia × 5, yellow
- 4 Swamp milkweed 'Ice Ballet' × 3, white
- 5 Purple gas plant × 1, pink
- 6 Palm sedge × 3, green leaves
- 7 Autumn crocus × 12, lavender
- 8 Giant snowdrop × 10, white
Why this plant
- The only trumpets. The others are daisies, dense clusters, flat plates and others. Shape reads at a distance, where colours blur.
- The only blue.
Why here
- At the back. At 2½ ft it is seen over mouse-ear coreopsis 'Nana' (8 in) in front of it, and has nothing behind it to hide.
- A step in the back row. Next to purple gas plant (3 ft) and swamp milkweed 'Ice Ballet' (3½ ft): no two neighbours there are the same height, so the back steps up and down like a skyline.
- 3 plants in one group. Massed, one kind reads as a single shape. Scattered, it would look spotty.
Why now
- In flower for 7 weeks. From early August to mid September.
- Fills a gap. For four of those weeks nothing else on the plan is in flower.
Planned as an English border: 5 of the 6 groups (83%) are drifts, longer along the bed than they are deep. Cool colours (blue, pink and lavender) with yellow as the warm note, and white to calm things between them. Neither end outweighs the other: the visual weight is split 44 to 56, left to right.
The planner's own design check: 13 Excellent, 3 Good, 1 Satisfactory. 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 willow gentian goes in a border
At 2½ ft it belongs in the middle of a bed. In the planner's ten height classes it is medium (24 in to 2½ ft).
Its job: drift. Planted in a small group of three or five, and repeated further along in the other number.
A gentian for the shady border: graceful, long-lived and easy in cool, moist, leafy soil. The arching habit suits a place beside a path, among ferns.
- Blue for late summer in shade
- Woodland gardens
- Planting with ferns
What to plant with willow gentian
Plants recorded as good partners for it, and what each pairing does:
- Japanese painted fern: its silver leaves are a setting for the flowers, before and after; low enough (18 in) to stand in front of it; happy in the same moist soil.
- Japanese forest grass: its green leaves are a setting for the flowers, before and after; low enough (18 in) to stand in front of it; happy in the same moist soil.
- Toad lily: happy in the same moist soil.
Questions about willow gentian
Does willow gentian need sun or shade?
Willow gentian grows in 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 willow gentian grow in?
USDA zones 5 to 7. It is hardy to zone 5, which means it survives winter nights down to about −10 °F (−23 °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 willow gentian flower in my zone?
In zone 5 it flowers early August to mid September. As a summer flower it moves about half a week for every zone: earlier where it is warmer.
| Zone 5 | Early August to mid September |
|---|---|
| Zone 6 | Early August to mid September |
| Zone 7 | Late July to mid September |
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 willow gentian be planted?
18 in (45 cm) apart, from the middle of one plant to the middle of the next. That is a little closer than its full width of 24 in (60 cm), so a group knits into one patch.
It grows 2½ ft (75 cm) tall. Give it the full distance from anything taller, or it will lean out towards the light.
How many willow gentian plants do I need?
At 18 in apart, set out in staggered rows:
- 5 to fill 10 square feet (about 1 m²)
- 7 for a single row 10 ft (3 m) long
- 17 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 three in one group.
Is there a native plant like willow gentian?
Willow gentian is not native to North America. These North American natives come closest to doing its job:
- Joe-Pye weed 'Baby Joe': the same job in a bed, the same size and the same flowering time; pink, not blue.
- Garden phlox 'Laura': the same job in a bed and the same size; flowers mid July to early September, purple, not blue.
- Turtlehead 'Hot Lips': the same job in a bed and the same flowering time; 6 in taller, pink, not blue.
Matched the way the planner's Swap button matches plants: the same job in a bed, then size, then flowering time.
What flowers after willow gentian?
Willow gentian is over by mid September. These start as it finishes and carry the same spot on, so it never goes flat:
- Toad lily: from mid September to mid October, 2½ ft tall (a recorded partner).
- Blue-stemmed goldenrod: from early September to mid October, 2½ ft tall.
- Blue wood aster: from mid September to mid October, 3 ft tall.
What does willow gentian look like in winter?
Willow 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
- Bottle gentian Gentiana andrewsii
- Crested gentian Gentiana septemfida
- Stemless gentian Gentiana acaulis
In these guides
Every fact on record
- Type
- Perennial
- Size
- 2½ ft (75 cm) tall, 24 in (60 cm) wide
- Plant
- 18 in (45 cm) apart
- Height class
- Medium (24 in to 2½ ft)
- Place in the bed
- Middle
- Flowers
- Early August to mid September; trumpets; blue
- Leaves
- Medium texture, herbaceous; green
- Shape
- Arching, clumping
- Hardy in
- USDA zones 5 to 7
- Light
- Part sun, part shade
- Soil
- Rich, evenly moist
- Water
- Moderate
- Feeding
- None needed
Not yet checked against an outside reference: its figures rest on general horticultural knowledge. 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.