• Photo of Houstonia caerulea (Houstonia caeruleas)

Plant Profile: Houstonia caerulea

Taxonomy: Houstonia caerulea

Names

Azure Bluet, Bluets, Common Bluets, Innocence, Quaker Ladies

  • Photo of Houstonia caerulea (Houstonia caeruleas)

Phonetic Spelling:hoos-TOH-nee-uh see-ROO-lee-uh

Genus:Houstonia

Species:caerulea

Family:Rubiaceae

Bluet is a perennial wildflower that typically reaches a height of up to 6 inches. Its leaves are arranged oppositely and feature smooth edges. The larger leaves grow at the base of the stem, while the smaller leaves are found along the stem. The plant produces striking blue flowers with yellow centers, which bloom from mid-spring through mid-summer. Although visually appealing, Bluet thrives best when planted in areas with minimal competition, such as along pathways, in lawns, or in bare spots. The rosettes that emerge in spring can also be transplanted.

This charming and delicate flower often appears in vibrant clusters of light blue. The Star Violet (H. pusilla), which grows up to 4 inches tall, features small purple flowers and can be found in fields and open woodlands stretching from South Dakota to Maryland, and further south to Florida and Texas. Another notable species, the Large Houstonia (H. purpurea), stands between 6 to 16 inches tall and has 3 to 5 ribbed, opposite, ovate leaves, along with white or pink flowers. This species is distributed from Nebraska to Maine and down to Florida and Texas, thriving in forests, lawns, and disturbed areas. Some of these Houstonia species have occasionally been classified under the genus Hedyotis.

Fire Risk: This plant is rated as having low flammability.

Regions: Mountain, Piedmont, Coastal Plains

Seasons of Interest:
- Blooms: Spring
- Nut/Fruit/Seed: Summer

Wildlife Value: Bluet is moderately resistant to deer damage, and its flowers attract bees, butterflies, and other pollinators.

Houstonia caerulea Feature Summary

Houstonia caerulea Image Gallery

Tags

#white
#yellow
#full sun tolerant
#small spaces
#annual
#blue
#perennial
#wildlife plant
#native bees
#low flammability
#NC native
#summer flowers
#fire resistant
#spring interest
#native wildflower
#wildflower garden
#food source herbage
#food source nectar
#food source pollen
#coastal FAC
#bird friendly
#nectar plant late spring
#food source hard mast fruit
#flies
#butterfly friendly
#nectar plant mid-spring
#Piedmont Mountains FACU
#partial shade tolerant
#pollinator garden
#bee friendly
#audubon

Similar Plants

Houstonia caerulea Feature Summary

Attributes
Eastern Canada and U.S.A.
Eastern US
Flowers are attractive to bees, butterflies, and other pollinators.
Perennial
low flammability
Fruit
Fruits are available April-August.
Flowers
Flower stems are unbranched. Flowers are blue and have a yellow center with four stamens attached to the corolla tube. Flowers bloom February-July.
White
Gold/Yellow
Blue
Spring
Summer
Winter
4-5 petals/rays
Tubular
Star
< 1 inch
Leaves
Leaves on the flower stem (opposite) are much smaller than those at the base (rosulate).
Opposite
Rosulate
Spatulate
< 1 inch
< 1 inch
Whole Plant Traits
Perennial
Annual
Native Plant
Wildflower
Herb
Multi-stemmed
Erect
Clumping
Cultural Conditions
Full sun (6 or more hours of direct sunlight a day)
Partial Shade (Direct sunlight only part of the day, 2-6 hours)
Dappled Sunlight (Shade through upper canopy all day)
Good Drainage
Moist
Occasionally Dry
Less than 12 inches
Coastal
Mountains
Piedmont
4a
4b
5b
5a
6a
6b
7a
7b
8b
8a
3a
3b
High Organic Matter
Loam (Silt)
Shallow Rocky
Landscape
Rock Garden
Butterfly Garden
Pollinator Garden
Native Garden
Small groups
Woodland
Lawn
Meadow
Naturalized Area
Small Space
Rock Wall
Coastal
Butterflies
Pollinators
Bees

Houstonia caerulea Attributes

Houstonia caerulea: Country Or Region Of Origin

Eastern Canada and U.S.A.

Houstonia caerulea: Distribution

Eastern US

Houstonia caerulea: Wildlife Value

Flowers are attractive to bees, butterflies, and other pollinators.

Houstonia caerulea: Particularly Resistant To (Insects/Diseases/Other Problems)

fire in the landscape.

Houstonia caerulea: Life Cycle

Annual
Biennial
Bulb
Perennial
Woody

Houstonia caerulea: Recommended Propagation Strategy

Division
Grafting
Layering
Leaf Cutting
Root Cutting
Seed
Stem Cutting

Houstonia caerulea: Fire Risk Rating

extreme flammability
high flammability
low flammability
medium flammability

Houstonia caerulea Fruit

Houstonia caerulea: Fruit Description

Fruits are available April-August.

Houstonia caerulea: Display/Harvest Time

Fall
Spring
Summer
Winter

Houstonia caerulea Flowers

Houstonia caerulea: Flower Description

Flower stems are unbranched. Flowers are blue and have a yellow center with four stamens attached to the corolla tube. Flowers bloom February-July.

Houstonia caerulea: Flower Color

filter_vintage
Blue
filter_vintage
Gold/Yellow
filter_vintage
White

Houstonia caerulea: Flower Bloom Time

Winter
Spring
Summer
Fall

Houstonia caerulea: Flower Petals

2-3 rays/petals
4-5 petals/rays
6 petals/rays
7 - 20 petals/rays
asymmetrical petals
Bracts
Colored Sepals
fused petals
more than 20 petals/rays
Tepals

Houstonia caerulea: Flower Shape

Bell
Cross
Crown
Cup
Dome
Funnel
Irregular
Lipped
Radial
Saucer
Star
Trumpet
Tubular
Urn
Wheel

Houstonia caerulea: Flower Size

1-3 inches
3-6 inches
< 1 inch
> 6 inches

Houstonia caerulea Leaves

Houstonia caerulea: Leaf Description

Leaves on the flower stem (opposite) are much smaller than those at the base (rosulate).

Houstonia caerulea: Woody Plant Leaf Characteristics

Broadleaf Evergreen
Deciduous
Needled Evergreen
Semi-evergreen

Houstonia caerulea: Leaf Color

spa
Green

Houstonia caerulea: Leaf Type

Compound (Pinnately , Bipinnately, Palmately)
Fronds
Needles
Sheath
Simple

Houstonia caerulea: Leaf Arrangement

Alternate
Opposite
Other/more complex
Rosulate
Whorled

Houstonia caerulea: Leaf Shape

Acicular
Auriculate
Cordate
Cuneate
Deltoid
Elliptical
Filiform
Lanceolate
Linear
Oblanceolate
Oblong
Obovate
Obtuse
Orbicular
Ovate
Palmasect
Palmatifid
Peltate
Pinnatifid
Pinnatisect
Reniform
Rhomboidal
Spatulate
Subcordate
Subulate

Houstonia caerulea: Leaf Margin

Crenate
Crenulate
Dentate
Denticulate
Doubly Crenate
Doubly Dentate
Doubly Serrate
Entire
Lobed
Serrate
Sinuate
Undulate

Houstonia caerulea: Hairs Present

No
Yes

Houstonia caerulea: Leaf Length

< 1 inch
1-3 inches
3-6 inches
> 6 inches

Houstonia caerulea: Leaf Feel

Fleshy
Glossy
Leathery
Papery
Prickly
Rough
Rubbery
Slippery
Smooth
Soft
Velvety
Waxy

Houstonia caerulea: Leaf Width

< 1 inch
1-3 inches
3-6 inches
> 6 inches

Houstonia caerulea Whole Plant Traits

Houstonia caerulea: Plant Type

Annual
Bulb
Carnivorous
Edible
Epiphyte
Fern
Ground Cover
Herb
Herbaceous Perennial
Houseplant
Mushroom
Native Plant
Ornamental Grasses and Sedges
Perennial
Poisonous
Rose
Shrub
Succulent
Tree
Turfgrass
Vegetable
Vine
Water Plant
Weed
Wildflower

Houstonia caerulea: Woody Plant Leaf Characteristics

Broadleaf Evergreen
Deciduous
Needled Evergreen
Semi-evergreen

Houstonia caerulea: Habit/Form

Arching
Ascending
Broad
Cascading
Climbing
Clumping
Columnar
Conical
Creeping
Dense
Erect
Horizontal
Irregular
Mounding
Multi-stemmed
Multi-trunked
Open
Oval
Prostrate
Pyramidal
Rounded
Spreading
Vase
Weeping

Houstonia caerulea: Growth Rate

Slow
Medium
Rapid

Houstonia caerulea: Maintenance

Low
Medium
High

Houstonia caerulea: Texture

Fine
Medium
Coarse

Houstonia caerulea Cultural Conditions

Houstonia caerulea: Light

Dappled Sunlight (Shade through upper canopy all day)
Deep shade (Less than 2 hours to no direct sunlight)
Full sun (6 or more hours of direct sunlight a day)
Partial Shade (Direct sunlight only part of the day, 2-6 hours)

Houstonia caerulea: Soil Drainage

Frequent Standing Water
Good Drainage
Moist
Occasional Flooding
Occasionally Dry
Occasionally Wet
Very Dry

Houstonia caerulea: Available Space To Plant

12 inches-3 feet
12-24 feet
24-60 feet
3 feet-6 feet
6-feet-12 feet
Less than 12 inches
more than 60 feet

Houstonia caerulea: NC Region

Coastal
Mountains
Piedmont

Houstonia caerulea: USDA Plant Hardiness Zone

thermostat
3a
thermostat
3b
thermostat
4a
thermostat
4b
thermostat
5a
thermostat
5b
thermostat
6a
thermostat
6b
thermostat
7a
thermostat
7b
thermostat
8a
thermostat
8b

Houstonia caerulea: Soil Texture

Clay
High Organic Matter
Loam (Silt)
Sand
Shallow Rocky

Houstonia caerulea Stem

Houstonia caerulea: Stem Is Aromatic

No
Yes

Houstonia caerulea Landscape

Houstonia caerulea: Landscape Theme

Asian Garden
Butterfly Garden
Children's Garden
Cottage Garden
Cutting Garden
Drought Tolerant Garden
Edible Garden
English Garden
Fairy Garden
Garden for the Blind
Native Garden
Nighttime Garden
Pollinator Garden
Rain Garden
Rock Garden
Shade Garden
Water Garden
Winter Garden

Houstonia caerulea: Design Feature

Accent
Barrier
Border
Flowering Tree
Foundation Planting
Hedge
Mass Planting
Screen/Privacy
Security
Shade Tree
Small groups
Small Tree
Specimen
Street Tree
Understory Tree

Houstonia caerulea: Resistance To Challenges

Black Walnut
Compaction
Deer
Diseases
Drought
Dry Soil
Erosion
Fire
Foot Traffic
Heat
Heavy Shade
Humidity
Insect Pests
Pollution
Poor Soil
Rabbits
Salt
Slugs
Squirrels
Storm damage
Urban Conditions
Voles
Wet Soil
Wind

Houstonia caerulea: Landscape Location

Coastal
Container
Hanging Baskets
Houseplants
Lawn
Meadow
Naturalized Area
Near Septic
Patio
Pond
Pool/Hardscape
Recreational Play Area
Riparian
Rock Wall
Slope/Bank
Small Space
Vertical Spaces
Walkways
Woodland

Houstonia caerulea: Attracts

Bats
Bees
Butterflies
Frogs
Hummingbirds
Moths
Pollinators
Predatory Insects
Reptiles
Small Mammals
Songbirds
Specialized Bees