Blue star creeper
Isotoma fluviatilis · Campanulaceae
A flat carpet of tiny green leaves sprinkled with pale blue, star-shaped flowers from late spring through summer. It tolerates foot traffic.
- Size
- 3 in tall, 18 in wide
- Zones
- 6 to 9
- Light
- Part sun to part shade
- Flowers
- Late May to early August
- Pets
- Toxic (mild)
- Job in a bed
- Carpet
A bed built around blue star creeper
The planner designed this bed around blue star creeper 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 blue star creeper stands where it does.
The plants
- 1 Blue star creeper × 17, blue
- 2 Mouse-ear coreopsis 'Nana' × 26, yellow
- 3 Swamp milkweed 'Ice Ballet' × 3, white
- 4 Northern sea oats 'River Mist' × 3, green
- 5 Globe arborvitae 'Danica' × 1, green leaves
- 6 Meadow saffron × 5, pink
Why this plant
- The only blue.
Why here
- On the front edge. At 3 in it frames the bed without hiding it, and it is in leaf all season. It finishes 60% of the edge.
- 17 plants in 5 runs (5, 5, 3, 3 and 1). Runs of different lengths make the edge a frame, not a ruled line.
Why now
- In flower for 12 weeks. From late May to early August.
- Fills a gap. For two of those weeks nothing else on the plan is in flower.
- One of two evergreens. They are what the bed has to show from November to March.
Planned as an English border: 5 of the 6 groups (83%) are drifts, longer along the bed than they are deep. The scheme leans cool (blue and pink) and uses yellow for warmth, with white and green to calm things between them. There is more mouse-ear coreopsis 'Nana' than anything else, 26 plants in all.
The planner's own design check: 10 Excellent, 7 Good.
Open this bed in the planner Change its size, the sun or the style, move plants about, or swap one for another.
Where blue star creeper goes in a border
At 3 in it belongs at the front of a bed. In the planner's ten height classes it is ground-hugging (up to 6 in).
Its job: carpet. A groundcover planted in threes and fives to cover the soil: along the front, and just behind it.
The best flowering carpet to walk on in moist soil. It creeps steadily, so edge it where it meets a lawn or a bed of small plants.
- Between stepping stones
- A lawn substitute for small areas
- Edging moist paths
What to plant with blue star creeper
Plants recorded as good partners for it, and what each pairing does:
- Mondo grass: its dark green leaves are a setting for the flowers, before and after; spires rising out of its mound; tall enough (8 in) to stand behind it.
- Irish moss: in flower together for six weeks, from late May; low enough (1 in) to stand in front of it; happy in the same moist soil.
- Sweet flag 'Ogon': its chartreuse leaves are a setting for the flowers, before and after; tall enough (10 in) to stand behind it; happy in the same moist soil.
Questions about blue star creeper
Does blue star creeper need sun or shade?
Blue star creeper 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, of average fertility, and a good soak in dry spells.
What zones does blue star creeper grow in?
USDA zones 6 to 9. It is hardy to zone 6, which means it survives winter nights down to about 0 °F (−18 °C).
Gardening in Canada? Use the USDA zone for your town: Canada's own zone map uses different numbers.
When does blue star creeper flower in my zone?
In zone 5 it flowers late May to early August. As a spring flower it moves about a week for every zone: earlier where it is warmer, later where it is colder.
| Zone 6 | Mid May to early August |
|---|---|
| Zone 7 | Early May to early August |
| Zone 8 | Early May to early August |
| Zone 9 | Late April to late July |
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 star creeper 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 18 in (45 cm), so a group knits into one patch.
It grows 3 in (8 cm) tall. Give it the full distance from anything taller, or it will lean out towards the light.
How many blue star creeper 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 threes and fives, along the front and just behind it.
In the bed above, the planner used 17 in five groups.
Is blue star creeper poisonous to dogs and cats?
Yes: mild toxicity to people, dogs and cats. May cause mild stomach upset if eaten. The sap can irritate skin and eyes.
Rated from NC State Extension. Where references disagree, the more cautious rating is used.
Is there a pet-safe plant like blue star creeper?
These come closest to doing what blue star creeper does, and no toxicity is recorded for them:
- Stemless gentian: the same job in a bed, the same size and the same colour; flowers early May to early June.
- Bugleweed 'Chocolate Chip': the same job in a bed, the same size and the same colour; flowers early May to late May, not evergreen.
- Mazus: the same job in a bed and the same size; flowers early May to mid June, lavender or white, not blue.
Matched the way the planner's Swap button matches plants: the same job in a bed, then size, then flowering time.
Do deer eat blue star creeper?
They may. NC State does not list it as resistant to deer or rabbits. Where they visit, protect it, or plant it among ones they avoid.
Will blue star creeper spread?
It spreads sideways, by runners or roots; the risk of it taking over is moderate. Spreads steadily by creeping stems. It is easy to pull out, but needs a firm edge.
What flowers after blue star creeper?
Blue star creeper is over by early August. These start as it finishes and carry the same spot on, so it never goes flat:
- Lilyturf: from early August to mid September, 16 in tall.
- Japanese anemone: from mid August to early October, 3 ft tall.
- Hosta 'Guacamole': from early August to late August, 24 in tall.
What does blue star creeper look like in winter?
Blue star creeper keeps its green leaves all winter, so it is one of the plants that hold a bed together from November to March, when the perennials have gone.
In these guides
- Plants you can walk on
- Garden plants toxic to cats
- Garden plants toxic to dogs
- Low plants for the front of a border
- Groundcover plants
- Evergreen perennials, ferns and grasses
- Long-flowering plants: 12 weeks or more
- Plants with blue flowers
Every fact on record
- Type
- Perennial (groundcover)
- Size
- 3 in (8 cm) tall, 18 in (45 cm) wide
- Plant
- 12 in (30 cm) apart
- Height class
- Ground-hugging (up to 6 in)
- Place in the bed
- Front
- Flowers
- Late May to early August; blue
- Leaves
- Fine texture, evergreen; green
- Shape
- Mat-forming, spreading
- Hardy in
- USDA zones 6 to 9
- Light
- Part sun, part shade
- Soil
- Average, evenly moist
- Water
- Moderate
- Feeding
- None needed
- Family
- Campanulaceae
- Comes from
- E.astern and Southeastern Australia
- Stands up to
- Foot traffic
Checked against NC State Extension and 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.