Ageratum houstonianum, more commonly known as floss flower, was first found growing in Mexico, where it tolerates the hot, dry climate admirably.
In the United States, ageratum is a tender annual, as it cannot survive cold winter temperatures.
Ageratum flower is one of the few annual plants to produce truly blue blooms, although some varieties are available with pink, white or lavender blossoms.
Starting Ageratum Houstonianum To grow Ageratum houstonianum, start seeds indoors eight to ten weeks before the last threat of frost.
Germination occurs in one to three weeks if light is allowed to reach the seeds.
Be sure not to cover them with soil or they may not sprout.
Transplant hardened-off seedlings into the garden once the danger of frost is over and the soil has warmed to a workable temperature.
Choose a sunny planting site with well-drained soil and space plants about 8 inches apart for the best results.
Caring for Ageratum Houstonianum Ageratum houstonianum plants are not typically bothered by pests or diseases, although spider mites may become a nuisance in hot weather.
Regular deadheading is required to keep the plants looking their best.
Some varieties, however, are self-cleaning and won't need as much attention.
Ageratum flower tolerates dry conditions, but performs best if watered when the leaves begin to droop.
Fertilizing and mulching are not necessary for this easy-care plant.
It's greatest strength in the flower garden is its ability to thrive, even when neglected.
Ageratum Houstonianum in the Landscape Because of its small size, the plant is best used for edgings and borders, small flower beds, containers and even rock gardens or xeriscapes.
For interesting garden design, try combining ageratum with pink begonias, marigolds or celosia flowers.
Petunia, lamb's ear and blue lobelia also seem to work well with Ageratum houstonianum.
Try planting with your favorite annuals and perennials to find what works best for your garden plans.