Hoary Alyssum

Description

Hoary alyssum is an upright herb that can grow up to 1m tall, single, or multiple stems with small whitish hairs that cover the stems and leaves. The leaves are lance-shaped, rough and fell like sandpaper, greenish in colour and clasp closely to the stem. It has small white flowers that grow in clusters with deeply notched petals. Oval seedpods are 5-8mm long, somewhat flattened, and held close to the stem. One plant can produce about 2,600 seeds.

Type

Biennial or short-lived perennial forb.

Habitat & Impacts

Hoary alyssum is found primarily on disturbed sites and prefers sandy or gravely well-drained sites. Hoary alyssum can be a serious problem for horse owners as the ingestion of sufficient quantities can cause a number of diseases in horses. This species can also become a serious problem on heavily used rangelands and may displace native vegetation, reducing forage production for wildlife and livestock.

Method of Spread

This species reproduces exclusively by seed which is produced in moderate amounts by each plant. Seeds are produced from the first flower in late spring right up until frost and are spread by wind and water.

Location

A number of sites are scattered throughout the Cariboo Chilcotin Coast region and all are small and localized. Sites currently exist at Alexis Creek, within the city of Quesnel and Williams Lake, and along Hwy 97 near Lac la Hache and 100 Mile House. Recent inventory has indicated that this plant is expanding throughout the Cariboo. Hoary alyssum is very prevalent and beyond control in the Barriere area within the Thompson Nicola Regional District to the east of our border.

Mechanical

Hand-pulling can effectively remove small infestations or cutting prior to seed set can control seed production.

Chemical

2,4-D Amine, dicamba, and mecoprop are effective at controlling hoary alyssum. This species has been difficult to control chemically in other areas of the province, possibly due to the timing of treatments.

Biological

There is no biocontrol agent available for control of hoary alyssum.

CCCIPC Priority & Treatment Strategy

Priority 1 (new invader) in all areas except the central coast where it is classed as N/A (not ecologically suited to the area) Since hoary alyssum is still a relatively new invader in the area, elimination of all sites is the goal.

Local Level

Hand-pulling small sites, herbicide for larger sites.

Landscape Level

Hand pulling small sites, herbicide for larger sites.