Invasive Flora of the West Coast: British Columbia and the Pacific Northwest

One

Herbaceous Plants

Alfalfa (Lucerne / Buffalo Herb / Purple Medic / Mu-Su / Jatt / Yonca)

Medicago sativa

pea family

Fabaceae

Description: Alfalfa is a deeply taprooted herbaceous perennial to 90 cm (3 ft.) in height. Its flowers are bluish purple and borne in terminal clusters arising from the leaf axils. The seed pods are brown and spirally coiled at maturity. The leaves are alternating, hairy, and pinnately compounded into three leaflets.

Traditional use: Alfalfa sprouts have in recent times become popular in salads and sandwiches. Chinese people have used alfalfa since the sixth century to treat kidney stones and to reduce fluid retention and swelling. Early American settlers used it to treat scurvy, cancer, boils, bedsores, and urinary and bowel problems.

Etymology: The genus name Medicago refers to Media, Ancient Persia, where the plant is thought to have first grown. The common name alfalfa is derived from the Arabic word alfalfas, which means father of all foods.

Origin: Introduced from Eurasia as a forage crop.

Season: Flowers from May to September.

Reproduction: By seed.

Concerns: Mainly a roadside weed.

American Black Nightshade (Small Flowered Nightshade)

Solanum americanum

potato family

Solanaceae

Description: American black nightshade is a herbaceous annual or short-lived perennial bush or sprawling vine up to 1.5 m (5 ft.) in height or length. Its leaves are variable in size to 10 cm (4 in.) long, alternating and arrow tip–shaped (ovate). The beautiful flowers are to 1 cm (0.5 in.) across and are generally white or sometimes blue to light mauve with contrasting yellow stamens. Green berries to 1 cm (0.5 in.) ripen to a shiny black.

Traditional use: The berries have long been an important food source for Indigenous Americans. Though it bears a close resemblance to deadly nightshade (A. belladonna), it is not poisonous

Etymology: The genus name Solanum is from the Latin sol [sun] and anus [to soothe].

Origin: South America.

Season: Flowers from May to June with ripe berries by July to September.

Reproduction: By seed; each plant is capable of producing up to 5,000 seeds.

Concerns: When allowed to grow in berry production farms, it reduces berry quality and quantity.

American Pokeweed (Common Pokeberry)

Phytolacca americana

pokeweed family

Phytolaccaceae

Description: American pokeweed is a herbaceous perennial up to 3 m (10 ft.) in height. Its flowers are white, five petalled, and borne in columnar clusters. The resulting fruit start off green and end a beautiful dark purple. The leaves are up to 15 cm (6 in.) long, alternating, and lanceolate.

Traditional use: Pokeweed has a long history among Indigenous groups. The young shoots and leaves can be boiled twice to remove any toxins and eaten like asparagus or spinach. The leaves become toxic as they age. Pokeweed root capsules are sold in modern-day herbal shops. They are considered a blood cleanser.

Etymology: The genus name Phytolacca is from the Greek phyton [plant] and lac, referring to the dye extracted from the lac insect. The common names pokeweed and pokeberry are derived from pocan, an Indigenous word for a plant that yields a dye.

Origin: Native to eastern North America.

Season: Flowers from July to August, with the berries ripening from September to October.

Reproduction: By seed and division.

Concerns: The raw berries and older leaves are poisonous to humans and livestock.

American White Waterlily (Fragrant Water-Lily / Beaver Root)

Nymphaea odorata

water-lily family

Nymphaeaceae

Description: American white waterlily has white or pink flowers up to 12 cm (5 in.) across. For photographers, the flowers open in the morning and close in the afternoon. The leaves are round and up to 25 cm (10 in.) across and like the flowers float on the surface of the water.

Traditional use: The roots, seeds, leaves, and flowers are edible and have been used as a food source and for medical uses for centuries by Indigenous Peoples across North America.

Etymology: The genus name Nymphaea means water-lily, inspired by the water nymphs of Greek and Roman mythology.

Origin: Originally an eastern/central aquatic plant in North and Central America, it is now seen as an introduced or naturalizing plant in the west.

Season: Depending on the area and elevation, flowers June to September with seeds ripening from August to October.

Concerns: Can very quickly take over freshwater ponds.

Annual Sow Thistle (Prickly Sow Thistle / Spiny Milk Thistle)

Sonchus asper

aster family

Asteraceae

Description: A taprooted annual up to 1.2 m (4 ft.) tall, with yellow flowers up to 2.5 cm (1 in.) across. It has ray florets only. The hairless floral bracts are borne in flat-topped clusters. The leaves are the identifying factor when distinguishing annual sow thistle from common sow thistle. Both have spiny-toothed margins on the leaves, but the bases of annual sow thistle’s leaves have large rounded flanges as they clasp the stem. With common sow thistle, the leaf bases are pointed as the leaves pass through the stem.

Traditional use: Like other sow thistles, the young leaves are excellent in soups, casseroles, and salads. The milky juice of all sow thistles is said to be a healthy wash for the skin.

Etymology: As the common name sow thistle suggests, it is a favourite food for pigs. The genus name Sonchus is derived from the Greek sonchos [hollow], referring to the hollow stems.

Origin: Introduced from Europe.

Season: Flowers throughout the summer, from June to September.

Reproduction: By seed.

Concerns: A problem in cultivated fields and a host of several plant viruses.

Argentinian Vervain

Verbena bonariensis

verbena family

Verbenaceae

Description: Argentinian vervain is a rapid seeding herbaceous perennial up to 1.8 m (6 ft.) in height. Its leaves are mostly lanceolate with serrated edges and up to 12 cm (5 in.) long. The flowers are lavender to mauve to purple and held up by square stems in terminal and axillary clusters up to 5 cm (2 in.) across.

Traditional use: The flowers of this attractive, drought-tolerant ornamental plant are excellent for attracting butterflies and honeybees. It has the Royal Horticultural Society’s Award of Garden Merit.

Etymology: The genus name Verbena is Latin for sacred bough, referring to verbena officinalis, which in ancient times were carried by priests. The species bonariensis is named for Buenos Aires, the capital of Argentina.

Origin: Tropical South America.

Season: Flowers by mid-summer and sets seeds by mid-August to October.

Reproduction: By seed.

Concerns: Once this plant disperses its mature seeds, the owner or caretaker of the gardens will forever be pulling out seedlings. It is on the invasive species watchlist for Washington State.

Bird’s-Foot Trefoil

Lotus corniculatus

pea family

Fabaceae

Description: Bird’s-foot trefoil is a sprawling herbaceous perennial up to 60 cm (24 in.) long. Its bright-yellow flowers are up to 1 cm (0.5 in.) long and are often red tinged. They are borne in rounded umbels with two to eight flowers on stalks up to 8 cm (3 in.) high. The brown seed pods are 2.5 cm (1 in.) long and radiate like spokes from the stem ends. The leaves are stalkless and pinnately compounded into five leaflets.

Traditional use: In the United Kingdom, a solution made from the plant was used for an eye wash.

Etymology: The species name corniculatus means horned, in reference to the spiked seed pods. The common name bird’s-foot trefoil refers to the similarity of the seed pods to a bird’s foot.

Origin: An escaped forage plant from Eurasia.

Season: Flowers from July to September.

Reproduction: By seed and rooting at the nodes.

Concerns: Not much of a problem yet; it is mainly seen along roadsides and in waste areas.

Bitter Dock (Butter Dock / Broad-Leaved Dock)

Rumex obtusifolius

buckwheat family

Polygonaceae

Description: Bitter dock is a large taprooted herbaceous perennial up to 1.2 m (4 ft.) in height. Its tiny flowers are a plain greenish brown and borne in dense elongated clusters. The basal leaves are up to 30 cm (12 in.) long, alternating, heart shaped at the base, and reduced in size upward.

Similar species: Clustered dock (R. conglomeratus) is very similar. It can be distinguished by its segmented flower clusters.

Traditional use: The young leaves can be used as potherbs, and the seeds can be dried, ground, and added to flour. Medicinally, the leaves were applied to burns, scalds, and nettle stings.

Etymology: Until modern times, the large leaves were used to wrap bricks of butter, hence the common name butter dock. The species name obtusifolius means blunt leaved.

Origin: Introduced from Eurasia.

Season: Flowers from June through summer.

Reproduction: By seed. Like curled dock, if the taproot is rototilled into the ground, the broken pieces will reproduce.

Concerns: Can be extremely invasive in moist lowland pastures.

Bittersweet (Woody Nightshade)

Solanum dulcamara

potato family

Solanaceae

Description: A perennial vine up to 3 m (10 ft.) in length. Its unique flowers are bluish purple with folded-back petals (corolla) exposing the yellow anthers. The flowers are borne in open umbrella-like clusters on stalks arising from the leaf axils. The berries are up to 1 cm (0.5 in.) long; they transition from green to orange to brilliant red. The upper leaves are up to 8 cm (3 in.) long and alternating, with two lobes at the base.

Traditional use: Bittersweet has been used to treat aches, whooping cough, arthritis, rheumatism, and asthma.

Etymology: The genus name Solanum is from the Latin word solor [quieting/ease], probably referring to the effects of its medicinal properties. The species name dulcamara literally translates as sweet bitter.

Origin: Introduced from Eurasia.

Season: Flowers from June to October.

Reproduction: By seed.

Concerns: It can reduce the value of bean crops. All parts of the plant should be considered mildly poisonous.

Broad-Leaved Peavine (Everlasting Pea / Perennial Sweet Pea)

Lathyrus latifolius

pea family

Fabaceae

Description: Broad-leaved peavine is a herbaceous perennial from rhizomes capable of climbing to 1.8 m (6 ft.). Its pea-like pink flowers are scentless and borne in terminal clusters on stalks arising from the leaf axils. The seed pods are up to 10 cm (4 in.) long and smooth and house ten to twenty-five seeds. The bluish-green leaves are up to 15 cm (6 in.) long, 5 cm (2 in.) wide, and pinnately compounded with two leaflets. At the top of their tips, the leaves are branched, curling tendrils by which the plant climbs.

Traditional use: Historically, the seeds were used in medicine.

Etymology: The genus name Lathyrus is from the ancient Greek thouros [excitable]. The species name refers to the broad leaves.

Origin: Introduced from Europe as a garden ornamental.

Season: Flowers from May to October.

Reproduction: By seed and rhizome.

Concerns: Not too much of a problem except in small gardens, where it can take over. All parts of the plant are considered poisonous.

Bull Thistle

Cirsium vulgare

aster family

Asteraceae

Description: Bull thistle is a well-armed biennial 0.9–1.8 m (3–6 ft.) in height. In its first year, it forms a ground-hugging rosette with a large taproot. In its second year, it bolts, producing an upright fibrous