Common Name: thoroughwort
Type: Herbaceous perennial
Family: Asteraceae
Native Range: Southwestern United States, northern Mexico
Zone: 7 to 10
Height: 1.00 to 1.50 feet
Spread: 1.00 to 2.00 feet
Bloom Time: July to October
Bloom Description: Blue
Sun: Full sun to part shade
Water: Medium
Maintenance: Medium
Suggested Use: Annual, Ground Cover, Naturalize
Flower: Showy
Attracts: Butterflies
Culture
Grow in medium moisture, well-drained loams in full sun to part shade. Best in full sun in St. Louis. Plants can spread somewhat aggressively by rhizomes in optimum growing conditions. This plant is winter hardy to USDA Zone 7. It will normally not survive a St. Louis winter, but may be grown in containers here. If grown in protected areas as an annual, it may stay in the garden from year to year by self-seeding.
Noteworthy Characteristics
Conoclinium greggii, commonly called Gregg’s blue mistflower and Texas ageratum, is a spreading ground cover that is native to Texas, New Mexico, Arizona and northern Mexico. It typically grows to 12-18” tall and spreads to 24” wide or more. Ageratum-like powder blue flowers bloom from summer to fall. Flowers have a misty appearance, hence the common name. Divided light green leaves. Flowers are very attractive to butterflies. Synonymous with and sometimes called Eupatorium greggii.
Problems
No serious insect or disease problems. Not winter hardy to St. Louis.
Uses
Where winter hardy, it makes an excellent ground cover for sunny areas. Grow as an annual or in containers in areas where not winter hardy.