Sky Blue Aster (Aster azureus)
ASS-ter azureus

Deciduous Perennial Upright, Bushy in the Asteraceae Family
A tough Midwest prairie native lighting up dry, sunny spots with clouds of sky-blue, yellow-centered flowers from late summer into fall — drought-tolerant and a magnet for native bees and butterflies.

Aster azureus (Symphyotrichum oolentangiense), commonly known as Sky Blue Aster, is a native Midwestern prairie perennial prized for its abundance of small, sky-blue to lavender, daisy-like flowers with bright yellow centers. Blooming from late summer into fall, it forms an airy, upright clump of wiry, often reddish stems and rough, sandpapery leaves, with the lower leaves distinctly stalked. More sun- and drought-tolerant than most blue asters, it thrives in dry to average, well-drained soil and is a dependable late-season nectar source for native bees, butterflies, and other pollinators.

Pros

  • Extremely drought-tolerant once established, ideal for dry, sunny sites
  • Reliable magnet for native bees, butterflies, and other pollinators
  • Long late-season bloom extends color into fall after most perennials finish
  • Self-seeds readily, naturalizing nicely in a prairie or meadow planting

Cons

  • Can self-seed aggressively in a small, tidy garden bed
  • Prefers full sun; gets leggy and blooms less in too much shade
  • Powdery mildew can appear on foliage in humid, crowded conditions
Why Like

In its native tallgrass prairies, savannas, and dry rocky woodlands across the central and eastern United States, Sky Blue Aster is one of the last major nectar sources of the year, sustaining migrating monarch butterflies and a wide range of native bees just before frost. Its abundant fluffy seed heads also feed songbirds like sparrows and juncos through the winter.
Highlights

One of the most drought-tolerant of the native blue asters, thriving in poor, dry, rocky soils where showier perennials struggle. A crucial late-season nectar source, blooming right as most other prairie flowers are finishing for the year.
 

Plant Data

Mature Size 18 - 36 inches tall. 18 - 24 inches wide.
Growth Rate Medium
Sun Exposure Partial Shade - Full Sun
Moisture Tolerance Dry - Medium:

Prefers dry to average moisture and is notably drought-tolerant once established; does not tolerate consistently wet or poorly-drained soil.
Zones 3a - 8b (Usually hardy to -40° F)
Tags Adaptable, Attracts Bees, Attracts Butterflies, Attracts Pollinators, Deciduous, Dry, Fall interest, Full Sun, Good for Butterfly Garden, Good for Rock Garden, Good for Rocky Soil, Low Maintenance, Medium, Naturalizing, Non-Allergenic, Partial Shade, Partial Sun, Perennial, Popular For Fall, Prairie Garden, Shade Tolerant
Bloom Period Late Summer To Fall
Flower Color Sky Blue To Lavender, Yellow Center
 

Plant Club Content
 

In The News

Commonly Planted with...

Pairs well with other late-season prairie natives such as goldenrod (Solidago), little bluestem (Schizachyrium scoparium), and prairie dropseed (Sporobolus heterolepis), whose warm golds and tans complement its blue flowers.
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Pricing and Availability History

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Past Availability
2025 : 04/13 - 10/04
2024 : 05/01 - 10/05
2023 : 04/13 - 09/30

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Field-Grown vs. Greenhouse-Grown Plants

Plants which are well-adapted to our local climate are most often field-grown (outside). Field-grown plants are generally cheaper and have the advantage of already somewhat acclimated to our cold winters, but that means they’re not artificially far along in the spring and tend to bloom at the normal time in our area.

Spring annuals and tender perennials are typically grown in Greenhouses so they can be ready and luxurious exactly when customers want them. Some perennials are also “forced” into early bloom in greenhouses. In May, there can be a very big difference between field-grown and greenhouse-grown plants of the same type. The latter typically look good right away (so they’re a great choice where that’s important), but we typically pay a premium for it.


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No Pricing or Availability Right Now

We order from a rotating cast of the best nurseries in the Great Lakes region. It looks like we've offered this plant in the past, but the nurseries we're working with this week don't appear to have it in stock at the moment.

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