Ageratum

Ageratum, or floss flower, is a frost-tender annual that forms low, rounded clumps topped with soft, tufted flower clusters. Blue is the most common color, with pink and white forms also available; it supplies long-lasting color in borders, bed edges, and containers through the warm season. ## Flowering and size The [North Carolina Extension Plant Toolbox](https://plants.ces.ncsu.edu/plants/ageratum-houstonianum/common-name/ageratum/) describes plants about 6–12 inches tall, with flowers from May through October; [Purdue Extension](https://ag.purdue.edu/department/hla/extension/extension-publications-library/ext-pubs/ho-80-w.html) gives a broader 6–18-inch height range and notes flowering from June into September in its regional annual-flower guide. Timing and mature size vary with cultivar and climate. The fine, green foliage forms a compact mound beneath the rounded flower heads. ## Site and soil Grow in full sun or partial shade. Ageratum performs best in rich, moist, well-drained soil and is suited to massed edging, low bedding, or containers. Taller selections can also be cut for arrangements. Keep plants from drying out during hot weather; good spacing helps air move through the planting. ## Maintenance Remove faded flower clusters for a tidier appearance and to encourage continued flowering. Watch for powdery mildew, especially where plants are crowded or foliage stays damp; water at soil level and provide adequate spacing.