Blue Star Japanese Aster

Light Needs

Partial Sun to Full Sun

(At Least 5 Hours of Direct Sunlight)

Mature Height

12-18 Inches

Mature Spread

18-24 Inches

Growing Zones

4 to 8

Blue Star Japanese Aster is a long-blooming perennial that keeps color going from early summer into fall. Botanically known as Kalimeris incisa 'Blue Star', it blooms earlier than true asters and forms a neat clump about 12 to 18 inches tall and 12 to 18 inches wide without leaning or sprawling. The light blue, daisy-like flowers have yellow centers and reach 1.5 inches across. Our garden designers often recommend it for sunny borders that need a steady ribbon of color rather than one heavy flush.

This herbaceous perennial handles heat, humidity, drought, and even clay soil with ease. Its compact mound of green foliage stays tidy through the season, and the flowers are useful for both cut and dried arrangements. Because it blooms for such a long stretch, it works well in cottage gardens, pollinator plantings, rock gardens, and smaller border spaces where a shorter plant still needs to carry visual weight. The open flowers also draw bees and butterflies, giving it extra value beyond flower color alone.

Blue Star Japanese Aster Care

Plant Blue Star Japanese Aster in full sun to part shade in well-drained soil with an acidic to neutral pH. It adapts to average garden soil and clay better than many flowering perennials, provided water does not sit around the roots. Full sun usually gives the best flowering and the strongest habit.

Water regularly while the plant is establishing; later let the top layer of soil dry a bit between deep soakings. Once rooted in, it handles dry spells well, although occasional watering in extended heat keeps blooming strong. A light spring feeding is plenty in most beds, and overly rich soil can lead to more leafy growth than flowers.

Pinch the stems lightly in early summer if you want a fuller plant with extra branching. After the main bloom cycle, shear back the spent flowers to tidy the mound and encourage another round of bloom later in the season. Divide clumps every few years in early spring when the center starts to thin or the planting needs freshening.

Blue Star Japanese Aster Spacing

Space plants 18 to 24 inches apart so the mounds can fill in while still getting enough airflow. For containers, use a pot at least 14 to 16 inches wide with free-draining soil and room for the clump to widen over time.

For companion planting, pair Blue Star Japanese Aster with tickseed and salvia for a sunny planting that keeps flowering through summer and holds together in heat. In containers, plant it with verbena and lantana so the lower, spreading flowers frame the soft blue blooms without crowding them.

Images Courtesy of North Creek Nursery

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