Hoary Alyssum (Berteroa incana)

Family - Mustard Brassicaceae
Life Cycle - biennial
Habitat - thrives on dry and disturbed ground on limestone and calcareous substrata with poor fertility, commonly found growing along roads and trails, gravelly stream and lake banks, in lawns, farmyards, and vacant lots, pastures and hayfields

Key Features

  • Small white flower petals are notched (giving petals a rabbit-ear shape)
  • Tiny star-shaped hairs that cover the plant (visible with a magnifying glass)
  • Leaves that are entire (the leaf edges are smooth, not toothed, divided or serrated)
  • Leaves on the flowering stems have no stalk, or a very small stalk
  • Seedpods point upwards, positioned close to the stem, rounded in shape and with a distinct membranous partition or septum

Identification

Hoary alyssum has a slender taproot capable of deep soil penetration. The basal rosette has oval to lance-shaped leaves that are broadest at the tip and 1 to 2 inches long. Flowering stems are erect or semi-erect growing 7 to 30 inches tall and are usually branched at the top. Multiple stems are common. Stem leaves are alternately arranged, similar to rosette leaves in shape, but generally point upward and are smaller with less of a stalk, or stalkless. The margins of all leaves are entire (smooth to slightly wavy) with no teeth or lobes.

Hoary alyssum flower bloom from early spring to late fall, given adequate water and light. The flowers are small with four ovate sepals that are green with white margins and four white petals that are narrow at the base, but spread upwards and have a notch at the tip. There are two short outer stamens and four long inner stamens, four nectaries, and one pistil with a long style. The seedpods are ellipsoid to ovoid, 0.2-0.3 inches long, slightly inflated with the persistent style at the tip. Flowers have long pedicels and are clustered at the stem tips in racemes. Seed pods point upward to touch or nearly touch the main flowering stem.

Each seedpod contains 4 to 12 dark reddish-brown, small lens-shaped seeds with narrow wings on the margins. The seedpod has two chambers divided by a translucent septum or membranous partition which remains on the pedicel after seed dispersla. The leaves, stmes, sepals, and seedpods are covered with star-shaped (stellate) hairs giving the plant a gray appearance from which the common name descriptor, hoary, is derived.

Juvenile
Juvenile
Mature
Mature
Flower
Flower