Narrow-leaved vervain (Verbena simplex) is a 4″ to 27½″ tall, erect, perennial forb. It grows in full sun in moderately dry to dry soil in upland prairies, hill prairies and old fields; on roadsides and railroad rights-of-way; and in other open, disturbed areas. It occurs in the United States from New Hampshire to Minnesota south to Texas and Florida, and in adjacent Canadian provinces. In Minnesota, where it is at the northwestern extent of its range, it has been recorded in only five counties. In two of those counties, the records are historical, and it is now presumed to be locally extinct (extirpated). It is listed as a special concern species in both Minnesota and Wisconsin.
Narrow-leaved vervain has one or more stems, narrow leaves, and a spiked inflorescence. The flowers are lavender or purple to white, or white tinged with blue, rarely white. Compared with the other three species of vervain found in Minnesota, narrow-leaved vervain is much rarer, is a much smaller plant, and has much narrower leaves.
Tall thistle (Cirsium altissimum) is a robust native plant. It can be 4′ to 10′ tall but in Minnesota it is usually no more than 7′ in height. It is found in prairies, open woodlands, roadsides, and disturbed sites. It has a patchy distribution in the lower two-thirds of Minnesota and is never common. It is absent from the far north and the Arrowhead region.
Tall thistle will easily pass the Native Thistle Test. Grasp the stem near the base of any native thistle loosely in your fist, then slide your fist upwards to just below the inflorescence. If the plant is a native thistle, you will not get a single prickle – it will be “ouchless”. If the thistle is thought to be an exotic (non-native) species, this test is not recommended.
Tall thistle looks similar to other native thistles. It can be distinguished by the stem that is green and not spiny; and the leaves that are white on the underside and are either unlobed or shallowly lobed.
Prickly tree clubmoss (Dendrolycopodium dendroideum) is an erect, evergreen, perennial, low-growing plant that looks like a miniature coniferous tree. It grows in northern forests and in shrubby areas recovering from fire or other disturbance. It often forms large colonies. In Minnesota it is common in the northeast, infrequent in the southeast, and mostly absent from the south and west.
Prickly tree clubmoss is usually no more than 6″ in height and has widely spreading branches. The branches are themselves up to four times branched—most branches have two or more secondary branches (branchlets), those branchlets are usually branched, those branchlets are often branched, and those branchlets are sometimes branched. The stem and branches are densely covered with prickly, needle-like leaves. Each fertile plant has 1 to 7 spore-bearing cones.
Several other Minnesota clubmosses are very similar in appearance. Prickly tree clubmoss is distinguished by lateral branches that are round in cross section, not flattened; stiff, prickly, widely spreading leaves on the lower part of the stem; and leaves on the branches that are all equal in size and arranged in six ranks, 2 above, 2 below, and one on each side.
Elm leafminer (Fenusa ulmi) is a very small common sawfly. It is native to eastern Europe and Scandinavia. It was brought to North America most likely on imported elms. It now occurs in the United States from New England to the upper Midwest, in the Pacific Northwest, and in southeast Canada. Based on the scarcity of reports, it is still relatively uncommon in Minnesota.
Due to the small size of the adult, elm leafminer is most often identified by the damage the larva causes to its host plant. Mines are seen from mid-May to early June on American elm and slippery elm. The larva feeds between the upper and lower surfaces of the leaf. It creates a serpentine mine at first. That soon develops into a small blotch between two lateral veins, later into a large blotch on one side if the midrib. The mines are clear and the flattened, whitish-green or yellowish-white larva can be seen when viewing the upper side of the leaf. The infected part of the leaf turns brown and eventually falls off. A heavy infestation may cause the entire tree to defoliate, but the infected tree flushes again and survives.
There are 76 species of Lycopodium worldwide. Only two of them occur in Minnesota. Running clubmoss (Lycopodium clavatum) is very widespread and common. It has a worldwide distribution, occurring on every continent except Australia and Antarctica. It is common in Minnesota in the Arrowhead region, infrequent in the north-central and central regions as far south as the northern metro, infrequent in the driftless area in the southeast, and absent from the remainder of the state.
Running clubmoss is an evergreen, perennial club moss. It produces a very long, creeping, horizontal stem and clusters of upright, branched stems. The stems are densely covered with narrow leaves that are arranged spirally and have a long hair at the tip.
Running clubmoss looks similar to its close relative, one-cone clubmoss. It can be distinguished by the cones that occur in groups of usually 2 to 5 and are arranged as a straight central axis with spreading to ascending side branches.
Western rock jasmine (Androsace occidentalis) is a small annual forb that occurs in North America between the Rocky Mountains and the Mississippi River. In Minnesota it is occasional in the western, southern, and central regions, absent from the northeast. It may be the smallest terrestrial wildflower native to Minnesota. It is usually no more than 3″ tall. It appears as a 1½″ in diameter radiating cluster of leaves and up to 15 leafless flower stalks. The flowers are white and about 1 ⁄16″ wide.
Western rock jasmine is short-lived, flowering from April to May and dying back by mid-summer. It is easily overlooked due to its diminutive size. For these reasons it may be more common than reported.
There are seventeen species of Diphasiastrum worldwide, five in North America, two in Minnesota. Fan clubmoss (Diphasiastrum digitatum) is the most abundant Diphasiastrum species in North America. It is common in eastern and north-central Minnesota. It grows in well-drained, moist to dry soil, in dappled sunlight to light shade, in open, upland, coniferous and deciduous woodlands, thickets, and sandy fields.
Fan clubmoss is a low growing shrubby evergreen. It produces both horizontal and erect stems, numerous branches that are held parallel to the ground, and cones at the end of long stalks. It is distinguished from other club mosses by horizontal stems that lie on the surface of the ground; branches that are flattened, are held parallel to the ground, and do not have narrow areas marking the start and end of annual growth; four ranks of leaves, those on the underside much smaller than those on the upper side; and sterile tips on about half of the cones.
Club mosses in the genus Diphasiastrum readily crossbreed with other species in the same genus. The hybrids that are produced are fertile. Fertile hybrids are common in the animal kingdom but rare in the plant kingdom.