Michaelmas Daisy

Year-round

Frost aster is a native perennial in the Pittsburgh area. It fills out over the growing season and produces a cloud of small white fall flowers, so give it a spot with room to spread.

• Plant in full sun to part shade. It handles the region's heavy clay soils and does not need rich garden soil.
• It spreads by seed and by rhizomes, so plan for it to fill in a bed over a few seasons or divide it if it gets more crowded than you want.
• Confirmed native to Pennsylvania by USDA PLANTS and the Lady Bird Johnson Wildflower Center.
• Deadhead spent flowers through the bloom season to keep the plant looking tidy and to extend flowering.

Edge the bed or contain the spread so the mature clump reads as an intentional planting rather than an overgrown patch. That keeps a front yard planting HOA-friendly.

Fall

Fall is when frost aster earns its name. It blooms from August into October, often right up to Pittsburgh's first frost.

• Expect small white, daisy-like flowers with yellow centers from August through October, continuing until the area's average first freeze around October 20.
• Deadhead if you want to limit self-seeding. This aster spreads readily by seed in the region's moist clay soils.
• The late blooms are one of the last nectar sources of the season for bees and other pollinators.
• Leave some spent flower heads standing into late fall for birds and overwintering insects.

A mass planting of the fall bloom reads as a deliberate flower bed rather than an unmown patch, which keeps it HOA-conscious for a front yard.

Winter

Frost aster dies back to the ground for Pittsburgh's cold winters and does not need special protection in this climate.

• Above ground growth dies back after hard frost, which is normal for this region's winter climate.
• The Pittsburgh area falls in USDA plant hardiness zone 6b, so this perennial is well matched to local winter lows.
• Leave the dead stems standing over winter for wildlife value, then cut them back in early spring.
• No mulching or winter protection is typically needed once plants are established in the region's clay soils.

Spring

In a Pittsburgh spring, cut back last year's dead stems and let new growth come up as frost risk fades toward late April.

• Cut old stems down to a few inches above the ground in early spring before new growth starts. This keeps the clump tidy and lowers disease risk.
• New growth typically appears in April, ahead of the area's average last freeze around April 25.
• Divide crowded clumps in early spring if the patch has spread further than you want.
• The region's clay soils hold spring moisture well, so extra watering is rarely needed this season.

Summer

Through Pittsburgh's warm, humid summer, pinch the stems back once or twice to keep frost aster bushy before it blooms in fall.

• Pinch or shear stems back by about a third from late spring into early July to keep growth bushy and less likely to flop.
• Stop pinching after mid-July. Pruning later than that delays the fall bloom and reduces flower count.
• Water during extended dry spells, otherwise the region's summer rainfall is usually enough.
• Give plants some airflow. Humid, still air can bring on powdery mildew on the leaves.