One of the tallest, Ageratum houstonianum 'Blue Horizon' (Floss Flower) features fluffy round clusters of lavender to purplish-blue flowers resembling asters. A very vigorous plant with strong, sturdy stems, many branches and larger flowers than the traditional ageratum. 

• A nonstop bloomer from mid summer to fall, it grows easily in shapely mounds, up to 18-30 in. tall (45-75 cm) with a spread of in. (20 cm) and mixes extraordinarily well with all other annuals and perennials.
• It is deer, rabbit resistant and attracts butterflies and makes great cut flowers.
• Easy to grow, Ageratum houstonianum performs best in full sun in rich soils with good drainage and consistent moisture during the growing season. Don't let it dry out! Avoid overhead watering and provide good air circulation to prevent the plant from powdery mildew. Light shade is tolerated in hot summer areas.
• Excellent choice for beds, borders, edgings, mass planting, rock gardens or groundcovers. Perfectly suited to mixed containers too. Excellent as cut flowers (on the taller varieties).
• Easily grown from seed, starting indoors in late winter and transplanting outdoors after the danger of frost has passed. Alternatively, seeds can be sown in the garden after the last frost date. If you prefer live plants, they are available from many nurseries.
• Deadhead spent flowers to keep the plant tidy and promote profuse blooming. In warm climates, Ageratum may self-sow.