Weeds to watch for in the Okanagan-Similkameen

Puncturevine seedpod (OASISS/file)
Hoary allysum growing next to a hayfield in Summerland (OASISS/file)
Hoary alyssum seed heads (OASISS/file)
Puncturevine flower and seedpod (OASISS/file)

Property owners in the Regional District of Okanagan-Similkameen (RDOS) are being encouraged to watch for two invasive plants that are on the move — puncturevine and hoary alyssum.

Puncturevine is a spiny annual that thrives in the summer sunshine and requires little rainfall to grow. It spreads low to the ground, with stems branching in all directions up to three metres in length. Tiny yellow flowers develop into seedpods with sharp spines. The spines stick painfully in bare feet and flatten bicycle tires and are easily transported in vehicle tires. The seedpods can also lodge into dogs’ paws and injure livestock.

The plant is typically found along road shoulders, gravel trails, vacant lots, beached and unpaved parking sites. It readily makes its way into agricultural lands, growing between rows of ground crops, tree fruits and grapevines.

In Osoyoos and Oliver, puncturevine is very widespread. However, other municipalities in the region have little or none. The RDOS asks residents to report any new sightings to your local municipal office, especially if bylaw enforcement is required.

Hoary alyssum is a tap-rooted plant with stems that reach heights of up to one metre. It spreads only by speed. Plants vary from simple, slender and unbranched to fully branched and rounded. While it is most common on sandy or gravelly soils, hoary alyssum establishes in dry, disturbed habitats, such as roadsides and railway embankments. It also grows in meadows, pastures and hayfields. Hoary alyssum can be found throughout the regional district.

Hoary alyssum’s white flowers appear in June and can continue blooming into the summer months, especially if plants are mowed. If horses consume large quantities of this plant, they may be troubled with fever, limb edema and laminitis. Most poisonings occur when hoary alyssum is mixed in alfalfa hay.

“These invasive plants can be contaminants of fill, gravel, sand, crushed stone and other aggregates, so be wary if you are importing such materials to your property,” states local biologist Lisa Scott, who’s also the executive director of the Okanagan and Similkameen Invasive Species Society (OASISS).

The best control method is to prevent establishment by destroying the first plants found in an area before seeds begin to form. Young plants can be removed by hoeing, shallow tillage or by carefully hand-pulling plants. Daisy (dandelion) grubbers are a great tool for popping up puncturevine plants. Removed plants should be bagged and taken to the landfill. Invasive plants should not be composted or added to your yard waste bins.

“Both puncturevine and hoary alyssum prefer areas of disturbed, bare ground. Reducing soil disturbance and re-seeding or planting with desirable species can help reduce opportunities for these unwanted plants to invade,” said Scott.

Municipalities and the regional district are working closely with OASISS to control outbreaks of these invasive plants throughout the region.

For further information on invasive species, go to www.oasiss.ca.

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Nature