Giant Aster is a striking perennial known for its impressive stature and profusion of late-season blooms. It brings vibrant, daisy-like flowers to the garden when many other plants fade, extending the gardening season.
Identifying Giant Aster
Giant Aster refers to taller varieties like Symphyotrichum novae-angliae (New England Aster). These robust plants often reach 4 to 7 feet, with a sturdy, upright, clumping habit. Their foliage is rough-textured and hairy, with leaves often clasping the stem.
Giant Asters produce abundant, daisy-like flowers with ray petals surrounding a yellow center. Colors range from purples, lavenders, to pinks, with white varieties available. They bloom from late summer (usually August) through fall (often until October), providing color as other plants finish their season. Flowers measure 1 to 2 inches in diameter.
Planting and Growing Giant Aster
Successful cultivation begins with proper site selection. Giant Asters thrive in full sun (at least six hours daily) for vigorous growth and abundant flowering. Air circulation helps prevent common fungal issues like powdery mildew.
Giant Asters prefer well-draining, consistently moist, fertile soil. While they adapt to various soil types, including heavier clay, drainage prevents waterlogging and root rot. Incorporating organic matter like compost improves soil structure and fertility.
Consistent watering is needed during dry periods to keep soil moist without waterlogging. One inch of water per week, from rainfall or irrigation, is sufficient for established plants. Watering at the base avoids wetting foliage, which can contribute to fungal diseases.
Giant Asters are not heavy feeders and generally do not require frequent fertilization. A light application of balanced fertilizer in spring, or mulching with well-rotted compost, supports healthy growth if soil is poor. Over-fertilization can lead to excessive foliage, reducing blooms.
Pruning enhances the plant’s appearance and performance. The “Chelsea chop,” cutting stems by one-third to one-half in late spring or early summer, encourages bushier growth and prevents flopping. This technique often results in more numerous, though smaller, flowers. Taller varieties may benefit from staking in exposed locations for support.
Giant Asters can be susceptible to powdery mildew, especially in humid conditions or poor air circulation. Adequate spacing and watering at the base help mitigate this. Spider mites can be an issue; regular inspection aids early detection and management.
Propagating Giant Aster
Giant Asters propagate well by dividing mature clumps, which rejuvenates older plants. This is best done in early spring as new growth emerges, typically every three years. Dig up the clump, then use a sharp spade or knife to divide it into smaller sections, ensuring each piece has healthy roots and stems. Replant divisions in new locations.
Another propagation method is sowing seeds, collected from mature plants in fall. Aster seeds often require cold stratification for germination. Seeds can be sown directly outdoors in late fall or early winter, allowing natural cold temperatures to stratify them, or indoors after artificial cold stratification. When sowing indoors, plant seeds 1 inch deep and keep the soil moist.
Benefits of Giant Aster
Beyond ornamental value, Giant Asters offer ecological benefits, especially as a late-season food source for pollinators. Their abundant blooms provide nectar and pollen for bees (including native bees) and butterflies (such as Monarchs) when other flowering plants finish blooming. This sustenance supports pollinators preparing for winter or long migrations.
Giant Asters contribute to garden biodiversity by supporting various wildlife. They serve as larval host plants for certain butterfly and moth species, aiding local insect populations. For landscape design, their height and vibrant fall colors add vertical interest to borders, naturalized areas, or native plant gardens, extending the garden’s appeal into autumn.