Blue corydalis 'China Blue'
Corydalis flexuosa 'China Blue' ·
Clusters of slender, tubular flowers in electric sky blue, a colour rare in any garden, over ferny, blue-green leaves in spring.
- Size
- 12 in tall, 12 in wide
- Zones
- 5 to 8
- Light
- Part shade to shade
- Flowers
- Late April to mid June
- Pets
- Not checked
- Job in a bed
- Drift
A bed built around blue corydalis 'China Blue'
The planner designed this bed around blue corydalis 'China Blue' when this page was made: a 12 × 6 ft (3.7 × 1.8 m) cottage garden in zone 6, part shade. It chose the other plants from the 513 that suit those conditions, and says below why blue corydalis 'China Blue' stands where it does.
The plants
- 1 Blue corydalis 'China Blue' × 8, blue
- 2 Blue star creeper × 20, blue
- 3 Turtlehead 'Hot Lips' × 5, pink
- 4 Japanese meadowsweet × 3, pink
- 5 Inkberry 'Gem Box' × 1, dark green leaves
- 6 Double snowdrop × 5, white
- 7 Snowdrop × 5, white
Why this plant
- Nothing here is unique to it. Its leaf, flower shape and colour are all on the plan already. Its case rests on where it stands and when it performs.
Why here
- Near the front. At 12 in it is the step between blue star creeper (3 in) in front and turtlehead 'Hot Lips' (3 ft) behind: each is seen over the one before.
- 8 plants in 2 groups (5 and 3). Seen again further along, the same plant ties the bed together.
Why now
- In flower for 8 weeks. From late April to mid June.
- Fills a gap. For four of those weeks nothing else on the plan is in flower.
- Leaves gone by midsummer. They die back and leave bare ground. A perennial that comes up late stands beside it, and grows over the gap.
Planned as a cottage garden: 22 of the 37 plants (59%), bulbs aside, stand alone or in groups of no more than five, small enough for the kinds to mingle. Blue star creeper repeats along the bed to tie it together. A cool scheme: blue, pink and white.
The planner's own design check: 11 Excellent, 4 Good, 2 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 blue corydalis 'China Blue' goes in a border
At 12 in it belongs at the front of a bed. In the planner's ten height classes it is low (6 to 12 in).
Its job: drift. Planted in a small group of three or five, and repeated further along in the other number.
It needs cool, moist, leafy soil and dies down in summer heat, to return in autumn. Where it is happy, in a cool woodland bed, nothing draws more comment.
- True blue for cool shade
- Woodland beds with ferns
- Spring containers
What to plant with blue corydalis 'China Blue'
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; happy in the same moist soil.
- Hosta 'June': its variegated leaves are a setting for the flowers, before and after; bold leaves against its fine ones; a low mound at the foot of its spires.
- Foamflower: in flower together for six weeks, from late April; a low mound at the foot of its spires; happy in the same moist soil.
Questions about blue corydalis 'China Blue'
Does blue corydalis 'China Blue' need sun or shade?
Blue corydalis 'China Blue' grows in part shade (2 to 4 hours of sun, mostly in the morning) and shade (less than 2 hours of direct sun, or bright dappled light).
It wants soil that stays evenly moist, rich in organic matter, and a good soak in dry spells.
What zones does blue corydalis 'China Blue' 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 corydalis 'China Blue' flower in my zone?
In zone 5 it flowers late April 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 5 | Late April to mid June |
|---|---|
| Zone 6 | Mid April to mid June |
| Zone 7 | Mid April to early June |
| Zone 8 | Early April to early June |
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 corydalis 'China Blue' be planted?
10 in (25 cm) apart, from the middle of one plant to the middle of the next. That is a little closer than its full width of 12 in (30 cm), so a group knits into one patch.
It grows 12 in (30 cm) tall. Give it the full distance from anything taller, or it will lean out towards the light.
How many blue corydalis 'China Blue' plants do I need?
At 10 in apart, set out in staggered rows:
- 17 to fill 10 square feet (about 1 m²)
- 13 for a single row 10 ft (3 m) long
- 55 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.
Is there a native plant like blue corydalis 'China Blue'?
Blue corydalis 'China Blue' is not native to North America. These North American natives come closest to doing its job:
- Creeping Jacob's ladder: the same job in a bed, the same size, the same flowering time and the same colour.
- Woodland phlox: the same job in a bed, the same size and the same colour; flowers late April to late May, medium leaves, not fine.
- Wherry's foamflower: the same job in a bed, the same size and the same flowering time; white, not blue, medium leaves, not fine.
Matched the way the planner's Swap button matches plants: the same job in a bed, then size, then flowering time.
What flowers after blue corydalis 'China Blue'?
Blue corydalis 'China Blue' is over by mid June. These start as it finishes and carry the same spot on, so it never goes flat:
- Astilbe: from late June to mid July, 24 in tall.
- Cranesbill 'Rozanne': from early June to early October, 18 in tall.
- Foxglove: from early June to mid July, 4 ft tall.
What does blue corydalis 'China Blue' look like in winter?
Blue corydalis 'China Blue' has long gone by winter: it dies down in summer, soon after flowering, and comes back in spring.
More Corydalis
- Fumewort Corydalis solida
In these guides
Every fact on record
- Type
- Perennial
- Size
- 12 in (30 cm) tall, 12 in (30 cm) wide
- Plant
- 10 in (25 cm) apart
- Height class
- Low (6 to 12 in)
- Place in the bed
- Front
- Flowers
- Late April to mid June; upright spires; blue
- Leaves
- Fine texture, summer-dormant; blue-green
- Shape
- Mounding, clumping
- Hardy in
- USDA zones 5 to 8
- Light
- Part shade, shade
- Soil
- Rich, evenly moist
- Water
- Moderate
- Feeding
- Light, in spring
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.