Students for Stewardship The Cork Board
← Back to the library

Ageratum

Ageratum houstonianum (a-ger-AE-tum ho-stone-ee-AE-num)

Family: Asteraceae Unknown Herbaceous (1-3 ft)

A frost-tender herbaceous annual to 1/2-1' tall, mounding with clusters of fluffy, aster-like flowers that should be planted with 10-12 inches of space. Genus name comes from the Greek "a" meaning not and " geras" meaning old age because the flowers hold their color for a long time. Forms clumping mounds with colors of pink, white & blue from May through October. Dependable flowering annual. Confused with ageratums that are perennials with tall, erect stems and leaves well-spaced out, but similar in appearance with leaves and flowers. This plant is moderately drought tolerance but prefers rich, moist, well-drained soil as well as full sun. It is good for beds and containers, blooming from spring to frost. Taller varieties make good cut flowers. This plant is seldom damaged by rabbits and deer. Used for edging or low massing plant in bed. Relative pest/disease free Insect Pests, Diseases, and Other Plant Problems: susceptible to powdery mildew. Some cultivars have shown excellent resistance to phytophthora. Quick ID Hints : Mounded herb as wide as tall, often 6" Terminal cluster of small heads Flowers all tubular, tassel-like

Source: NC State Extension Gardener Plant Toolbox ↗ NC State Extension Gardener Plant Toolbox, 50 attributes.

How it fits the guild

Guild layer 4 - Herbaceous (1-3 ft)
See companions & conflicts ↓

Companions & Conflicts

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 niche Catharanthus roseus Petunia x hybrida Salvia rosmarinus

Full plant profile

Growing Conditions
Plant type
Annual
Life cycle
Annual
USDA zones
2a, 2b, 3a, 3b, 4a, 4b, 5a, 5b, 6a, 6b, 7a, 7b, 8a, 8b, 9a, 9b, 10a, 10b, 11a, 11b
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
High Organic Matter
Soil drainage
Good Drainage | Moist
Available space
Less than 12 inches
Mature size
Height: 0 ft. 6 in. - 1 ft. 0 in. | Width: 0 ft. 10 in. - 1 ft. 0 in.
Growth rate
Medium
Canopy layer
4 - Herbaceous (1-3 ft)
Form & Appearance
Foliage
Deciduous
Leaf color
Green
Leaf type
Simple
Leaf arrangement
Opposite
Leaf shape
Cordate; Deltoid; Obtuse; Ovate
Leaf margin
Crenate
Hairs present
Yes
Leaf detail
Alternate, ovate to deltoid, pilose on both sides to slightly downy, obtuse, cordate, crenate.
Flower color
Blue; Pink; White
Flower value
Good Cut; Showy
Flower form
Cyme
Flower shape
Tubular
Flower size
< 1 inch
Flower detail
Fluffy, aster-like flowers that grow in clusters. Most commonly blue but can be pink or white. Terminal in clustered cymose heads; heads 1/4" diameter; Involucral bracts imbricated in several series. Lavendar, blue to pink, or white, tubular with 5 small lobes; pistils exerted, styles forked.
Bloom time
Fall; Summer
Fruit type
Achene
Fruit detail
Fruit is a cypsela which is a type of achene.
Stem color
Green; Red/Burgundy
Stem detail
Semidecumbent, sometimes branched, green to reddish.
Wildlife & Ecology
Native status
Unknown
Origin
Central America
Wildlife value
Plant is seldom damaged by deer or rabbits and attracts butterflies.
Attracts
Butterflies; Pollinators
Play value
Wildlife Food Source
Food & Medicine
Fruit type
Achene
Landscape Use
Landscape location
Container
Landscape theme
Butterfly Garden; Drought Tolerant Garden; Pollinator Garden
Garden tags
#drought tolerant #summer annual #rabbit resistant #blue flowers #white flowers #full sun tolerant #pink flowers #deer resistant #summer flowers #fantz #pollinator plant #butterfly friendly #partial shade tolerant #bedding plants #container plant #cutting garden #annual #wildlife friendly #HS303 #hortcontest #fpp
Problems & Resistance
Insect problems
Whiteflies Found on Flowers and Foliage; Aphids Found on Flowers and Foliage
Disease problems
Southern Bacterial Wilt on Herbaceous Ornamental Plants
Problems
Weedy
Resistant to
Deer; Drought; Rabbits
Particularly resistant to
Rabbits, deer, and drought. Some cultivars resistant to phytophthora.

Planted at Hunnicutt

Nobody’s planted this one yet.