Japanese primrose
Primula japonica ·
A candelabra primrose: whorls of crimson, pink or white flowers stacked in tiers up a tall stem in late spring, above a rosette of big, lettuce-like leaves. It needs wet soil.
- Size
- 20 in tall, 14 in wide
- Zones
- 4 to 8
- Light
- Part sun to part shade
- Flowers
- Mid May to late June
- Pets
- Toxic (mild)
- Job in a bed
- Drift
A bed built around Japanese primrose
The planner designed this bed around Japanese primrose when this page was made: a 12 × 6 ft (3.7 × 1.8 m) cottage garden in zone 6, part sun. It chose the other plants from the 367 that suit those conditions and its wet soil, and says below why Japanese primrose stands where it does.
The plants
- 1 Japanese primrose × 5, red
- 2 Himalayan fleeceflower 'Darjeeling Red' × 5, pink
- 3 Polyanthus primrose × 20, yellow
- 4 Garden phlox 'David' × 3, white
- 5 Turtlehead 'Hot Lips' × 5, pink
- 6 Inkberry 'Gem Box' × 1, dark green leaves
- 7 Winter aconite × 8, yellow
Why this plant
- The only bold leaves here. The rest are medium and fine. A change of leaf keeps plants distinct when nothing is in flower.
- The only red.
Why here
- At the back. At 20 in it stands behind the taller inkberry 'Gem Box' (2½ ft).
- A step in the back row. Next to turtlehead 'Hot Lips' (3 ft) and garden phlox 'David' (3½ ft): no two neighbours there are the same height, so the back steps up and down like a skyline.
- 5 plants in one group. Massed, one kind reads as a single shape. Scattered, it would look spotty.
Why now
- In flower for six weeks. From mid May to late June.
- Fills a gap. For five of those weeks nothing else on the plan is in flower.
Planned as a cottage garden: 30 of the 39 plants (77%), bulbs aside, stand alone or in groups of no more than five, small enough for the kinds to mingle. The bed is balanced: the left half carries 52% of the visual weight and the right half 48%. There is more polyanthus primrose than anything else, 20 plants in all.
The planner's own design check: 9 Excellent, 8 Good.
Open this bed in the planner Change its size, the sun or the style, move plants about, or swap one for another.
Where Japanese primrose 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.
In wet, shady ground it seeds into drifts of mixed colours, which is how it looks best. It will not tolerate drying out, even briefly.
- Stream sides and bog gardens
- Moist woodland
- Naturalising in wet shade
What to plant with Japanese primrose
Plants recorded as good partners for it, and what each pairing does:
- Japanese iris: medium leaves against its bold ones; tall enough (3 ft) to stand behind it; happy in the same wet soil.
- Marsh marigold: flowers first, mid April to early May, so the spot is never empty; medium leaves against its bold ones; a low mound at the foot of its spires.
- Ostrich fern: its green leaves are a setting for the flowers, before and after; medium leaves against its bold ones; tall enough (4 ft) to stand behind it.
Questions about Japanese primrose
Does Japanese primrose need sun or shade?
Japanese primrose 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 moist to wet soil, rich in organic matter, and plenty of water.
What zones does Japanese primrose grow in?
USDA zones 4 to 8. It is hardy to zone 4, which means it survives winter nights down to about −20 °F (−29 °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 Japanese primrose flower in my zone?
In zone 5 it flowers mid May to late June. As a spring flower it moves about a week for every zone: earlier where it is warmer, later where it is colder.
| Zone 4 | Late May to late June |
|---|---|
| Zone 5 | Mid May to late June |
| Zone 6 | Early May to late June |
| Zone 7 | Early May to mid June |
| Zone 8 | Late April to mid 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 Japanese primrose 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 14 in (35 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 Japanese primrose 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 five in one group.
Is Japanese primrose poisonous to dogs and cats?
Yes: mild toxicity to dogs, cats and horses. Can cause mild vomiting in pets if eaten.
Is there a pet-safe plant like Japanese primrose?
These come closest to doing what Japanese primrose does, and no toxicity is recorded for them:
- Virginia bluebells: the same job in a bed and the same size; flowers mid April to early May, blue, not red.
- Crocosmia 'Emily McKenzie': the same job in a bed; 4 in taller, flowers early August to mid September.
- Hardy orchid: the same job in a bed and the same flowering time; belongs at the front, not in the middle, 4 in shorter.
Matched the way the planner's Swap button matches plants: the same job in a bed, then size, then flowering time.
Will Japanese primrose spread?
It seeds itself about; the risk of it taking over is moderate. Self-seeds freely. Remove the spent flowers to limit seedlings.
What flowers after Japanese primrose?
Japanese primrose is over by late June. These start as it finishes and carry the same spot on, so it never goes flat:
- Japanese iris: from late June to mid July, 3 ft tall (a recorded partner).
- Astilbe: from late June to mid July, 24 in tall.
- Black-eyed Susan: from mid July to mid September, 24 in tall.
What does Japanese primrose look like in winter?
Japanese primrose 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 Primula
- Cowslip Primula veris
- Drumstick primrose Primula denticulata
- English primrose Primula vulgaris
- Orchid primrose Primula vialii
- Polyanthus primrose Primula x polyantha
- Siebold's primrose Primula sieboldii
In these guides
- Plants for wet soil and rain gardens
- Garden plants toxic to cats
- Garden plants toxic to dogs
- Plants with spires: vertical accents
- Plants for a white garden
Every fact on record
- Type
- Perennial
- Size
- 20 in (50 cm) tall, 14 in (35 cm) wide
- Plant
- 12 in (30 cm) apart
- Height class
- Medium short (18 to 24 in)
- Place in the bed
- Middle
- Flowers
- Mid May to late June; upright spires; red, pink, white
- Leaves
- Bold texture, herbaceous; green
- Shape
- Upright, self-seeding
- Hardy in
- USDA zones 4 to 8
- Light
- Part sun, part shade
- Soil
- Rich, moist to wet
- Water
- High
- Feeding
- Moderate, 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.