By Patsy Cotterill
We have four common Anemone species in the Parkland area, if you include two that were formerly in the genus Anemone: prairie crocus (formerly Anemone patens, now included in the genus Pulsatilla as Pulsatilla nuttalliana) and Anemonastrum canadense (formerly and still, according to Flora of North America, Anemone canadensis).
Prairie crocus is well known to many people, so here I plan to take a look at the other three species, all good candidates for the native plant garden. But first some characteristics of the genus as a whole.
Anemones are herbaceous perennials in the buttercup family, Ranunculaceae, with long-stalked basal leaves and stem leaves that characteristically form a whorl or collar (an involucre) at the base of an inflorescence of long-stalked flowers. Usually there is more than one involucre of leaves subtending flower stalks, giving the appearance of tiers along the stem. The leaf blades are three- to five-divided into often wedge-shaped, toothed lobes in the shape of a hand (palmate). Basal and involucral leaves resemble each other.
The flower consists of only one ring of flower parts, the sepals, which are usually white or yellowish or purplish. The stamens are numerous and the many small ovaries in the centre of the flower will form a head consisting of densely-packed, one-seeded fruits called achenes.
The three species under consideration in this article are Canada anemone (Anemonastrum canadense), cylindrical anemone (Anemone cylindrica) and long-headed anemone (Anemone virginiana var. cylindroidea). Both the latter two species have also gone by the common name thimbleweed.
Canada anemone
Of the three, Canada anemone is the most distinctive. It is lower-growing than the other two and because it is rhizomatous it tends to spread and form patches. The long-stalked basal leaves are deeply divided into three to five lobes (but are not compound, i.e., divided fully to the midrib). With large basal leaves and often two tiers of involucral leaves the plant looks very leafy. It can have a single main (primary) involucre of stalkless leaves subtending a long-stalked single flower, or additional stems with involucres subtending smaller, stalked flowers. The sepals are large and bright white, making a pleasant contrast to the dark green leaves. The head of achenes is round and the minutely winged achenes are hairless, or if hairy, only shortly and sparsely so.
Canada anemone occurs in wetter habitats than the other two, preferring moist meadows, depressions and shady spots that retain moisture. It flowers earlier than the thimbleweeds in June, compared to July for the other two, although the flowering times of all three can overlap. This plant makes a great ground cover where moisture is adequate and can be a good choice for edges where there is sufficient shade to prevent the soil from drying out.
The thimbleweed anemones
By contrast, A. cylindrica and A. virginiana are tall, erect plants reaching up to 80 cm in height, and lack rhizomes. The species are very similar, so telling them apart is a challenge. Both, at least our geographic variety of A. virginiana, var. cylindroidea, have similar habitats, such as grassland, dry woods and waysides.
Both species have long-stalked basal leaves which, however, are deeply incised down to the midrib (so are compound), with the same palmate arrangement, but the lobes are narrower and more deeply incised giving a finer look than in Anemonastrum canadense. In A. cylindrica the yellowish sepals curl inwards at the edges and are silky-hairy on the outside: sepals are more likely to be white in A. virginiana.
Both species have single flowers arising on long flower stalks from between an involucre of stalked leaves. A key character often given in flower guides is that A. cylindrica has one involucre of stem leaves whereas A. virginiana has two, but in fact this is misleading. Both species have several long (10-30 cm) flower stalks arising from the primary involucre and several of these bear a secondary involucre with a shorter flower stalk and the usual single flower. All flowers reach approximately the same height, which makes for a more impressive floral display.
The shape of the fruiting head is a diagnostic character. In A. cylindrica it is narrow and cylindrical and in A. virginiana it is ovoid or ellipsoid-oblong. In both species the achenes are covered in a white wool, and the fruiting head often persists into the winter, often making for an attractive feature when covered in snow or hoar frost. With a magnifying lens and ruler, the species can be seen to differ somewhat in length of achene beak. In A. cylindrica it is shorter (0.5-1 mm) than in A. virginiana (1-1.5 mm).
Anemone cylindrica ranges across Canada and into much of the US. The typical variety of A. virginiana (var. virginiana) is widely distributed in North America, but var. cylindroidea occurs across the Prairies and in parts of eastern Canada. Both species are reported to occur in the Edmonton area, with A. cylindrica apparently being the more common.
Other species of Anemone occur in Alberta but are confined mostly to the mountains. The exception is cut-leaved anemone (A. multifida) which grows in local grasslands, and with its purple flowers and finely divided leaves also makes a good garden specimen.
Have fun searching out the fruits of these three species as their flowers fade and fruits begin to ripen in July and August! Clifford E. Lee is likely a good place to look for all three species.