Asters are a popular and beautiful choice for garden landscapes, offering vibrant blooms that bring color and life to outdoor spaces. These striking flowers, often resembling daisies, are particularly cherished for their abundant display in the fall.
Why Asters Excel in Landscaping
Asters are an excellent choice for landscaping due to their significant contribution of late-season color, filling gardens with vibrancy when many other plants begin to fade. They serve as important attractors for pollinators, such as bees and butterflies, providing a crucial nectar source as these insects prepare for winter. These perennials are hardy and low-maintenance once established, adapting well to various conditions. Their ability to extend the visual appeal of a garden into autumn makes them a valuable addition to any landscape.
Selecting Aster Varieties for Your Landscape
Choosing the right aster variety involves considering their mature size, bloom characteristics, and preferred growing conditions.
New England Aster (Symphyotrichum novae-angliae) is a robust option, growing 3 to 7 feet tall with hairy leaves and showy flowers ranging from purple to pink or white with yellow centers, blooming from late summer to late fall.
New York Aster (Symphyotrichum novi-belgii) presents as a shorter plant, reaching 1.5 to 5 feet, with smooth leaves and flowers in shades of blue-violet, rose, or white.
Smooth Blue Aster (Symphyotrichum laeve) grows 2 to 4 feet tall and wide, featuring attractive smooth blue-green foliage and daisy-like flowers that are light blue to violet with yellow centers, blooming from late summer to early fall. This variety is noted for its ability to remain upright without staking.
Heath Aster (Symphyotrichum ericoides) is a more compact, bushy perennial, 1 to 3 feet tall, characterized by numerous small, white, star-like flowers with yellow centers that can cover the plant from late summer to mid-fall. It is adaptable to drier, well-drained soils.
Designing with Asters
Asters integrate well into various garden styles, including cottage gardens, pollinator gardens, and native plant landscapes. For borders, mass plantings of asters create a striking visual impact, especially when their vibrant fall colors are in full display. Grouping asters together enhances their presence, while layering them with other plants adds depth and texture to the design.
Effective companion plants for asters include ornamental grasses like switchgrass or little bluestem, which provide height and movement. Goldenrod (Solidago) blooms alongside asters, offering a complementary golden hue and supporting late-season pollinators. Coneflowers (Echinacea) and sedum also pair well, sharing similar care needs and contributing contrasting forms and textures. Considering color schemes, purple asters can be beautifully contrasted with the yellow of sunflowers or rudbeckias.
Planting Asters for Success
Most aster varieties thrive in full sun, meaning at least six hours of direct sunlight daily. While some asters can tolerate partial shade, ample sunlight promotes more abundant blooms. Soil preparation involves ensuring good drainage and enriching the soil with organic matter, such as compost. Asters prefer well-draining, loamy soil with a neutral to slightly acidic pH.
When planting, dig a hole slightly larger than the root ball and position the aster at the same depth it was growing in its container. Proper spacing is crucial; plants should be set 12 to 18 inches apart to allow for good air circulation and growth, which can also help prevent disease. After planting, water the asters thoroughly to help them establish. Applying mulch around the base helps retain soil moisture and suppresses weeds.
Ongoing Care for Thriving Asters
Consistent watering is important for asters, particularly during dry spells, with about one inch of water per week recommended. It is important to maintain consistently moist but not soggy soil, as both overwatering and underwatering can cause issues like leaf loss or reduced flowering. Watering the plants at their base rather than overhead helps to prevent fungal diseases.
Fertilizing is often minimal; a thin layer of compost applied around the plants each spring is usually sufficient to encourage vigorous growth. Over-fertilization, especially once blooming begins, can sometimes shorten the flowering period. Pruning techniques significantly impact aster health and appearance. Pinching back the growing tips by one-third in late spring or early summer encourages bushier growth, more blooms, and can delay flowering for an extended display. Deadheading spent flowers improves the plant’s appearance and can prevent unwanted self-seeding. General garden hygiene, such as removing dead or wilting stems, also contributes to overall plant health.
Addressing Common Aster Landscaping Challenges
Asters can encounter common issues, including fungal diseases and pests.
Fungal Diseases
Powdery mildew appears as a white or gray-white powdery substance on leaves and stems, often favored by high humidity and poor air circulation. To manage this, ensure proper plant spacing for good air circulation, avoid overhead watering, and consider using fungicidal treatments or a baking soda solution. Rust causes tan to brown spots on leaves, and can be addressed by improving air flow and removing affected foliage.
Pests
Pests such as lace bugs and aphids can also affect asters, though they typically do not cause severe damage. Regular inspection and prompt removal of infested leaves can help control these pests.
Physiological Problems
Physiological problems like legginess can occur, especially in taller varieties or those grown in insufficient light. Pinching back plants early in the season can promote a more compact, bushier habit. A lack of blooms might indicate inadequate sunlight, improper watering, or excessive fertilization, requiring adjustments to care routines to encourage flowering.