Blue blossom is an easy to grow broad leaf evergreen shrub in the buckthorn (Rhamnaceae) family that, left to its own devices, will grow to a large, tree-like 20 feet high and wide. However, it has a short trunk and spreading branches that can be controlled to spread to a few feet tall. In natural settings, it is ofen found on wooded slopes and canyons, in the neighbourhood of streams, and in evergreen forests of California and Oregon. Blue blossom has truly blue flowers which all gardeners know can be incredibly difficult to find. It can be used for screen and background plantings in large spaces and on slopes. This shrub is very low maintenance and can be used for a ground cover and for erosion control. The evergreen leaves stay put and the blue flowers fall off individually and are easily blown away by the slightest wind. The densly packed foliage provides excellent cover for songbirds. The genus name comes from keanothos , an ancient Greek name relating to some plants in the buckthorn family. The specific epithet thyrsiflorus means "flowers arranged in a thyrse", in reference to the shape of the infloresence ( thyrsus is the name of the staff, adorned with leaves and berries, that belonged to Bacchus, the Greek god of wine). Blue blossom is a hardy plant, but it dislikes root disturbance and it should be planted in its permanent site. It is a fast-growing plant that flowers when young. It dislikes heavy pruning and it is best not to cut out any wood thicker than a pencil. Keep in mind when pruning that the plant flowers on the previous year's growth and any pruning is best done immediately after flowering. Constant pruning to keep Blue blossom small can shorten its life. Diseases, Insect Pests, and Other Plant Problems: No known diseases or insect pests. May freeze with colder winters. Elk and deer will browse the foliage.
Curated pairwise relationships between this plant and others in the library — who feeds
whom, who competes, who confuses the pests. Green reads as a good pairing, red as one to avoid.
No curated interactions recorded for this species yet.
Also noted by NC State
Related species the NC State Plant Toolbox flags for this plant — look-alikes to tell
apart, and plants that play a similar role in a planting. Ones we carry in the library are linked.
Fills a similar nicheIlex glabraIlex vomitoria 'Dwarf'Rubus idaeus subsp. strigosus
Full plant profile
Growing Conditions
Plant type
Shrub
Life cycle
Perennial
USDA zones
5a, 5b, 6a, 6b, 7a, 7b, 8a, 8b, 9a, 9b
Light
Full sun (6 or more hours of direct sunlight a day) | Partial Shade (Direct sunlight only part of the day, 2-6 hours)
Soil texture
Loam (Silt); Sand
Soil pH
Acid (<6.0); Alkaline (>8.0); Neutral (6.0-8.0)
Soil drainage
Good Drainage | Moist | Occasionally Dry
Available space
6-feet-12 feet
Mature size
Height: 4 ft. 0 in. - 14 ft. 0 in. | Width: 5 ft. 0 in. - 14 ft. 0 in.
Growth rate
Rapid
Maintenance
Low
Canopy layer
3 - Shrub (3-15 ft)
Form & Appearance
Habit / form
Dense; Irregular; Prostrate; Rounded; Spreading
Texture
Fine
Foliage
Broadleaf Evergreen
Leaf color
Green
Leaf type
Simple
Leaf arrangement
Alternate
Leaf shape
Elliptical; Ovate
Leaf margin
Serrate
Leaf feel
Glossy
Leaf value
Long-lasting
Leaf size
3-6 inches long, < 1 inch wide
Hairs present
No
Leaf detail
The elliptic to ovate leaves have finely serrated margins and can reach 1.5 inches long and 0.5 inches wide. Three prominent veins on the underside, tip obtuse to acute, margin sometimes gland-toothed.
Flower color
Blue; Purple/Lavender; White
Flower value
Showy
Flower form
Spike
Flower size
1-3 inches
Flower detail
Blossoms from mid-May to mid-June with spike-like clusters of blue flowers. Just before buds open they are pinky-lavender.
Bloom time
Spring
Fruit color
Brown/Copper; Purple/Lavender
Fruit type
Capsule
Fruit value
Edible
Fruit size
< 1 inch long
Fruit detail
Seeds ripen from August to October. Fruit is small, glandular-sticky, slightly lobed.
Wildlife & Ecology
Native status
Native
Origin
Southwestern North America
Distribution
Oregon to Mexico
Wildlife value
The flowers attract hummingbirds, honey and bumble bees and butterflies. Seeds are a food source for birds and small mammals.
Attracts
Butterflies; Hummingbirds; Small Mammals; Songbirds