Japanese hop (Humulus japonicus) is an invasive, prohibited noxious weed in Minnesota. It can form dense mats several feet deep covering and inhibiting the growth of all other vegetation. It is relatively new in the state. The first recorded sighting was in 1992. To date, it has been reported in just four counties in the southeastern corner of the state, and in Hennepin and Scott Counties in the metro area.
Japanese hop closely resembles the native common hop (Humulus lupulus). Japanese hop is distinguished by the leaf stalk that is as long or longer than the blade; the leaf blade that has 5, 7, or 9 lobes and is rough to the touch on the underside; the stiff hairs on the margins of the bracts on the fruiting structure; and the lack of stalked, yellowish glands on the fruiting bracts, anthers, and seed capsules. Also, unlike common hop, the fruiting structure is not fragrant when crushed, and it cannot be used for making beer.
Pst on Canada thistle
Visitors to Minnesota’s natural places will occasionally come across a stand of Canada thistle with a few plants that are whitened at the top, appearing bleached. The discoloration is caused by the bacterium Pseudomonas syringae pv. tagetis. It has been called “White‐colour Disease of Canadian Thistle,” “apical chlorosis of Canada thistle,” and “Bacterial Speck”, but it has no widely-accepted common name. It is often referred to in scientific literature as Pst.
Outside of a laboratory, a bacterium is recognized only by the symptoms it produces in its host. Pst produces the substance tagetitoxin, which blocks the production of chloroplasts, preventing photosynthesis. This results in whitened plant growth (chlorosis) on only the upper portion of the plant, stunted growth, fewer shoots, and inhibition of flowering. Pst infects plants in the Aster family, including Canada thistle, common dandelion, common sunflower, common ragweed, giant ragweed, Jerusalem artichoke, and some other plants not found in Minnesota.
Researchers at the University of Minnesota conducted a study in 2002 to assess the viability of using Pst as a biological control agent for Canada thistle.
Many species of orchids are found in Minnesota prairies, but only three are prairie specialists: western prairie fringed orchid, Great Plains ladies’ tresses, and small white lady’s slipper. They all occur in lime-rich sediments deposited by glaciers and in clay-rich soils of glacial lake beds.
Small white lady’s slipper (Cypripedium candidum) is widely scattered but uncommon across the Great Lakes states to the Dakotas and adjacent Canadian provinces. Minnesota is the core area of the species and may have more individual plants than all other states and provinces combined. It is found in relatively undisturbed, high-quality prairies in the western, southern, and metro regions of the state.
Small white lady’s slipper produces small flowers that are easily overlooked. The best time to see it in bloom is … right now, the last week of May in southern Minnesota and the first or second week of June in the north.
There are six Asian bush honeysuckles that have been introduced into North America and are now naturalized here. Three of these, Bell’s, Morrow’s, and Tartarian honeysuckle, are found in Minnesota. A fourth, Amur honeysuckle, has spread to Wisconsin and Iowa and will probably reach Minnesota soon.
In the past, Bell’s honeysuckle (Lonicera x bella) was widely planted in eastern and mid-western North America, including Minnesota, to control erosion and as an ornamental. It has since spread aggressively to a broad range of natural and semi-natural habitats. It leafs out early in the spring, grows vigorously and large, crowds other plants, shades the ground, and uses available soil moisture and nutrients. It may also release a chemical into the soil that further inhibits the growth of other species.
Bell’s honeysuckle is a horticultural cultivated fertile hybrid of Morrow’s honeysuckle and Tartarian honeysuckle. As a hybrid, it shares characteristics of both of its parents, and is difficult to distinguish from them. Bell’s honeysuckle is identified by its leaves, which are sparsely to moderately hairy on the underside, at least along the main veins; and by the minute bractlets at the base of each flower, which are at least half as long as the ovary which they subtend.
There are about 75 species of spurred gentian (genus Helenia) worldwide. Only two occur in North America north of Mexico. Only one, American spurred gentian (Halenia deflexa ssp. deflexa), is found in Minnesota.
American spurred gentian is an often overlooked member of the Gentianaceae (gentian) family. Its flowers are much smaller and less showy than the more common bottle, pleated, and fringed gentians. It blooms in northern Minnesota under partial shade in moist coniferous forests (especially at the edges), cedar swamps, and bogs, and on river banks. It is often encountered on woodland trails that are wide enough to allow some sunlight to filter through.
From July to August American spurred gentian produces clusters of green to yellowish, often purplish-tinged flowers. The flowers have four petals, each of which has a long, downward-pointing spur at the base. There are no similar species in Minnesota.
There are at least 78 species of bladderpod (genus Physaria) recognized in North America. Most of them are restricted to western United States. Only Louisiana bladderpod (Physaria ludoviciana) is found in Minnesota. The natural range of this plant is from Montana and North Dakota, south to New Mexico and Arizona, and north to Manitoba and Saskatchewan. In Minnesota it is found in full sun growing on sandy soil on steep, south-facing, weathered, dolomitic sandstone bluffs. Spring Creek Prairie SNA has one of the largest known populations. Most of the other populations are within the city limits of Redwing.
Louisiana bladderpod is is common in its natural range but is classified as endangered in Minnesota and Illinois, threatened in Wisconsin. The few known populations in Minnesota may have been transplanted by a seed dropped by a bird, or may have survived from a time when the central plains extended into the area long ago.
Louisiana bladderpod is identified by its narrow, unlobed leaves forming a basal rosette; yellow flowers; and inflated, hairy, more or less globe-shaped fruit. There are no similar species in Minnesota.
Marsh skullcap (Scutellaria galericulata) is a common and widespread plant in wetlands across North America. It is found throughout Minnesota in wet meadows, marshes, bogs, fens, swamps, stream banks, pond edges, and roadside ditches. It is often overlooked as its weak stems lean against nearby plants and its blue flowers, though showy, appear sparsely.
There are five skullcap species in Minnesota. Marsh skullcap is distinguished by its leaves which are narrow, no more than ¾″ wide, shallowly round-toothed, very short stalked or stalkless, and pinnately veined with lateral veins that branch and rejoin before reaching the margin; flowers more than ½″ long rising from leaf axils but not at the end of the stem; and its preference for wetlands.
Four-flowered yellow loosestrife (Lysimachia quadriflora) is a slender, non-woody, flowering plant. It is common in moist and wet prairies across eastern North America. In Minnesota it is found throughout the state except for the Arrowhead region.
When not in flower, the foliage of four-flowered yellow loosestrife is easily overlooked among the taller prairie grasses. The stem is slender and the opposite leaves are narrow, up to 3½″ long but no more than ¼″ wide. The flower arrangement often appears as a whorl of four flowers, each one pointing in a different direction and nodding at the end of a slender stalk. In late summer the flowers are replaced by a shiny, globe-shaped, seed capsule with a long sharp spine at the tip. The capsule ripens in the fall.
Four-flowered yellow loosestrife is identified by the narrow leaves, nodding yellow flowers, and globe-shaped fruit capsule. When in flower, it is similar in appearance to fringed loosestrife (Lysimachia ciliata) and whorled loosestrife (Lysimachia quadrifolia). Both of those species have much wider leaves.
Photo by Randy
Kentucky coffee tree (Gymnocladus dioicus) has the largest leaves of any tree in Minnesota. They are 12″ to 36″ long, up to 24″ wide, and twice compound with 40 to 100 leaflets. They are the latest to appear in the spring in Minnesota and one of the first to drop in autumn.
Kentucky coffee tree is uncommon or rare wherever it is found. The large fruit pods of Kentucky coffee tree are probably an adaptation to large mammals of the Pleistocene epoch. Horses, giant sloths, mastodons, and mammoths were present on the North American continent for millions of years. They probably ate the pods and dispersed the seeds in their scat. They disappeared in the Late Pleistocene extinction event, 20,000 to 10,000 years ago, when all large mammals (over 2,200 pounds) in North America went extinct.
Kentucky coffee tree is identified by its large, twice-compound leaves with 40 to 100 leaflets; and the thick, somewhat flattened, 3″ to 6″ long fruit pod.
Celandine (Chelidonium majus) is native to Europe, Asia, and North Africa. It was introduced and cultivated in eastern North America as an ornamental. It occasionally escapes cultivation and is now well established in moist woodlands from Maine to Ohio south to Virginia. It is uncommon in Minnesota.
Celandine is found in full sun to light shade in moderately moist woodlands, thickets, hedge rows, roadsides, railroads, and waste places. It produces small clusters of bright yellow, 4-petaled flowers from May to August. There is a double-flowered form of this plant that produces flowers with 12 to 24 petals each. The sap is bright yellow or yellowish-orange and toxic. It is a skin irritant and has been used medicinally to treat warts.
Celandine is easily identified by its leafy stems with 5- to 9-lobed leaves; bright yellow, 4-petaled flowers; and ascending, slender, hairless seed capsules. There are no similar species in Minnesota.