Rachel Turnquist/Sask Ag

Description

Photo: Kandra Forbes

Tansy is a flowering herbaceous plant with finely divided compound leaves and yellow, button-like flowers. It has a stout, somewhat reddish, erect stem, usually smooth, 50–150 cm tall, and branching near the top. The leaves are alternate, 10–15 cm long and are pinnately lobed, divided almost to the center into about seven pairs of segments, or lobes, which are again divided into smaller lobes having saw-toothed edges, giving the leaf a somewhat fernlike appearance. The roundish, flat-topped, button-like, yellow flower heads are produced in terminal clusters from mid-to-late summer. The scent is similar to that of camphor with hints of rosemary. The leaves and flowers are toxic if consumed in large quantities; the volatile oil contains toxic compounds including thujone, which can cause convulsions and liver and brain damage. Some insects, notably the tansy beetle Chrysolina graminis, have resistance to the toxins and subsist almost exclusively on the plant.

Tansy is native to Eurasia; it is found in almost all parts of mainland Europe. It is absent from Siberia and some of the Mediterranean islands. The ancient Greeks may have been the first to cultivate it as a medicinal herb. In the sixteenth century it was considered to be "necessary for a garden" in Britain.

Photo: Glenn Barclay

It is a herbaceous perennial plant growing to 1-1.2 m tall, with several stems branched from the base. The stems are smooth, hairless or slightly hairy. The leaves are small, lanceolate, 4-8.5 cm long and up to 1 cm broad, with a slightly wavy margin. The flowers are small, produced in umbels with a basal pair of bright yellow-green petal-like bracts. Clusters of the bracts appear in late spring, while the actual flowers do not develop until early summer. All parts of the plant contain a toxic white milky sap.

It reproduces readily by seeds that have a high germination rate and may remain viable in the soil for at least seven years. The seed capsules open explosively, dispersing seed up to 5 m from the parent plant, and may be carried further by water and wildlife. Leafy Spurge also spreads vegetatively from the root system, which is complex, reported to reach 8 m into the ground and 5 m across, and may have numerous buds.

Photo by: Rachel Turnquist/ Sask Ag.

While most commonly found as a weed, toadflax is sometimes cultivated for cut flowers, which are long-lasting in the vase. Like snapdragons (Antirrhinum), they are often grown in children's gardens for the "snapping" flowers which can be made to "talk" by squeezing them at the base of the corolla.

The plant requires ample drainage, but is otherwise adaptable to a variety of conditions. It has escaped from cultivation in North America where it is a common naturalised weed of roadsides and poor soils; it is listed as an invasive species in several U.S. states and Canadian provinces.

Photo by: John Hauer/Sask Ag.

The lower cauline leaves are smaller, pinnately lobed; the upper leaves become much reduced, sessile, serrate to entire. The heads are numerous terminating the branches. Flowers are pink to purplish, the marginal ones not enlarged. The outer and middle involucral bracts are broad, striate, smooth with broadly rounded tips; the inner bracts are narrower with hairy tips. Pappus present with bristles 6–11 mm long. Fruit is a whitish, slightly ridged achene.

Russian knapweed is a deep-rooted long lived perennial. Some stands have been in existence for 75 years. It forms dense colonies in cultivated fields, orchards, pastures, and roadsides.

A native to Eurasia, Russian knapweed was introduced into North America in the late 19th century. Absent only from southeastern U.S., it has become widespread in other regions, especially in the western United States.

Photo by: Glenn Barclay

This plant has been designated as a noxious weed in Saskatchewan.

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Photo by: Glenn Barclay. This picture shows plants that are somewhat related. Pasture Sage is on the left. Biennial Wormwood is in the centre and Absinthe is on the right. Absinthe is grey, scented and has rounded leaf tips whereas biennial wormwood is a much deeper green, has pointy leaf tips and does not stink.

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Featuring John Hauer, Forage Specialist out of NB.

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Photo by: Glenn Barclay

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Photo by: Glenn Barclay

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Photo by: Glenn Barclay

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