A Prickly Subject

With a baby and a toddler a lot of small jobs go by the wayside, including the removal of a large, weedy bull thistle from our front yard. It bloomed a while ago, and Dave decided to take a picture of it. Despite its thorny character, the thistle flower, with its purple crown, is a thing of beauty.

Thistles are a prickly subject. Canada thistle, in particular, is considered a noxious weed in many countries, including Canada, the U.S., Australia, New Zealand and Brazil. This pesky thistle easily takes over farm fields and pastures and can be hard to remove.

Names can be deceiving, and Canada thistle, like most thistles in our area, is actually introduced from Europe. There are several species of thistle in our province, but on Vancouver Island, there are three that are most often encountered: Canada thistle, bull thistle, and edible thistle. The latter is a native species.

Canada thistle (Cirsium arvense) spreads by creeping underground stems (rhizomes) that make it particularly difficult to eradicate. This thistle has thin stems and numerous small pink-purple flowers with bracts that are not prickly. Canada thistle is the only thistle with male and female flowers found on separate plants. The leaves are spiny along the margin, but not on the leaf surface. Canada thistle frequents agricultural fields, roadsides and waste places.

Bull thistle (Cirsium vulgare) is generally larger than Canada thistle. It has a deep carrot-like taproot, and the leaves are covered in spines. The stems are winged, which means that they have a flat, papery margin. Bull thistle has large, handsome flowers. The bulbous part of the flower head, beneath the purple flowers, is covered in spiky bracts. Like Canada thistle, bull thistle frequents habitated areas, and is usually found at low to middle elevations.

Harder to find is the native edible thistle (Cirsium edule). This thistle is usually encountered up in the mountains, in moist meadows, clearings or talus slopes. Edible thistle grows from a taproot, and has flowers that are nodding when young. Like other thistles, the flowers are pink-purple, but the bracts are very cob-webby. It is always a delight to find this thistle when hiking in the subalpine. Another native species, the short-styled thistle (Cirsium brevistylum), sometimes hybridizes with edible thistle. The differences between edible thistle and short-styled thistle are subtle, so it is best to consult a good plant identification guide.

Thistles are in the sunflower (Asteraceae) family. A typical daisy flower has ray flowers and disc flowers. The ray flowers are the petals, and the disc flowers are the central part. Thistles only have disc flowers, and no ray flowers, which gives them a distinctive look. Directly beneath the flowers are bracts, tiny modified leaves that are tightly overlapping.

When the thistle goes to seed the thistledown is blown away by the wind. Thistle seed is a favourite food for birds, especially gold finches, and can be purchased for feeders. Thistle flowers are also a source of nectar for bees and butterflies, and are a larval food plant for some butterfly species. Almost all thistles are edible to humans if the stems and roots are peeled.

The thistle is the national flower of Scotland. Legend has it that in the year 1263, under the leadership of King Haakon of Norway, Norsemen planned to attack sleeping Scottish clansmen. To approach in silence under the cover of darkness, the Norsemen removed their shoes. One of the men stepped on a thistle and shrieked out in pain, thus waking the Scotts, who then won the battle, known as the Battle of Largs.

The word thistle comes from the Anglo-Saxon word thistle or pistel, which is derived from an Indo-European word meaning “to prick.”

Here in Canada, thistles are largely considered to be pernicious weeds. In Scotland, however, thistles are revered as a symbol of strength and heraldic power. Like many things, it is all a matter of perspective. Now that I’ve had a chance to admire the bull thistle in the front yard, I’m not sure what to do with it. For now, perhaps I’ll just let it go to seed.

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