Ontario Wildflowers website

Frost Aster
Symphyotrichum pilosum
(formerly Aster pilosus)

Frost Aster (Symphyotrichum pilosum) Other common names: Frostweed Aster, Hairy White Old Field Aster, Heath Aster, Old Field Aster, Pringle's Aster

Other scientific names: Aster pilosus

Family: Composite Family (Asteraceae)

Group: Asters

Distinctive features: Very fuzzy stem, as if coated with a thick frost.

Similar species:
  •   Panicled Aster (Symphyotrichum lanceolatum) - Stem not as hairy.

  •   Purple-stemmed Aster (Symphyotrichum puniceum) - Stem not as hairy, and often purple.

Flowers: Summer, Autumn;  White;  7 or more parts (petals);  1-2cm in diameter. Ray flowers: 16-47, usually white. Disc flowers: 20-40, whitish-yellowish, becoming purple. Flowers arranged in an open manner, very similar to Panicled Aster (Symphyotrichum lanceolatum). Bracts are stiff, long-pointed, and usually spreading.

Leaves: Alternate, Simple, Entire;  Long lance-shaped, very similar to Panicled Aster.

Height: Up to 1 m (1-4 ft)

Stem: Extremely hairy - coated with numerous dense hairs that stick straight out. Looks sort of like a thick frost has coated the stem. Most obvious when viewed with backlighting, ie the sun shining from behind the stem. Just to make things interesting, there is a variety of this species that has a smooth stem! Branches stiff.

Habitat: Fields and Open Areas, Meadows;  Moist low areas, fields or wooded.

Grows in Sun/Shade: Sun

Lifespan: Perennial.  

Books: Newcomb's Wildflower Guide: 458   

Native/Non-native: Native

Status: Common.

Notes: The striking and distinctive feature of this species is the very hairy stem. BUT there is a variety of this species that has a smooth stem! This variety can get misidentified as Panicled Aster.

Origin and Meaning of Names:
 Scientific Name: pilosum: soft; hairy

Photographs: 161 photographs available, of which 16 are featured on this page. SCROLL DOWN FOR PHOTOGRAPHS.

Range Map is at the bottom of the page

Frost Aster (Symphyotrichum pilosum)

Here's why this Aster is called Frost Aster. The stems and leaves are very hairy, so much so that they almost appear to be coated with a thick frost, especially when viewed with the sun shining from behind the stem.

Frost Aster (Symphyotrichum pilosum)

Another picture of the fuzzy stem. Frost Aster is sometimes confused with Purple-stemmed Aster (Symphyotrichum puniceum), which can also have a very fuzzy stem, and is not always purple. However, there are other differences to help tell these two asters apart.

Frost Aster (Symphyotrichum pilosum)

The stem viewed without the backlighting. It really is incredibly hairy.

Frost Aster (Symphyotrichum pilosum)

A leaf. Note that it too is very fuzzy.

Frost Aster (Symphyotrichum pilosum)

This photo shows the overall form of the Frost Aster. In this aspect it resembles Panicled Aster (Symphyotrichum lanceolatum). The branches spread out, and are often horizontal to the ground. The plants will sometimes be found leaning this way and that.

Frost Aster (Symphyotrichum pilosum)

Closeup view of a Frost Aster flower. Note the purple disc - they start out yellow, and gradually turn purple.

Frost Aster (Symphyotrichum pilosum)

Flower arrangement.

Frost Aster (Symphyotrichum pilosum)

The flowers are relatively large, as seen here.

Frost Aster (Symphyotrichum pilosum)

Sometimes the flowers appear rather sparsely along the flower stems, with just one or two flowers in bloom at once on each stem.

Frost Aster (Symphyotrichum pilosum)

Frost Aster (Symphyotrichum pilosum)

This photo shows the spreading phyllaries (green bracts below the flowers).

Frost Aster (Symphyotrichum pilosum)

Frost Aster (Symphyotrichum pilosum)

A closer view of the phyllaries.

Frost Aster (Symphyotrichum pilosum)

A nice meadow full of Frost Aster in late September.

Frost Aster (Symphyotrichum pilosum)

Here are: Left: Frost Aster (Symphyotrichum pilosum)
Right: Heath Aster (Symphyotrichum ericoides).

Frost Aster (Symphyotrichum pilosum)

Frost Aster roots.

Range map for Frost Aster (Symphyotrichum pilosum)

PLEASE NOTE: A coloured Province or State means this species occurs somewhere in that Province/State.
The entire Province/State is coloured, regardless of where in that Province/State it occurs.

(Range map provided courtesy of the USDA website and is displayed here in accordance with their Policies)