Thursday, July 27, 2023

Plant profile: Jumpseed

Persicaria virginiana, formerly Polygonum virginianum, Antenoron virginianum, Tovara virginiana


Jumpseed, also called Virginia knotweed or woodland knotweed, is a perennial herbaceous plant native to the eastern U.S., including southeast and east central Minnesota. It thrives in the damp soils and part shade of deciduous woods and edges, often where there has been some disturbance. These plants were growing along a trail through a woodland.

From July into September, the plants produce long, slender racemes bearing tiny, whitish flowers, each just a few millimeters across when fully open. After pollination by honeybees, bumble bees, leaf-cutting bees, and other bees and wasps, the flowers form small fruits that are deflexed – they angle downward on their short pedicels (flower stalks), a tensioned position that needs only a slight touch to be released. When it is, the fruits “jump” off the plant. Their hooked ends, formed by remnants of their styles, can latch on to fur or clothing and help the seeds travel farther from their parents.

Jumpseed flowers in mid to late summer, producing slender racemes up to 16 inches (40 cm) long. The small flowers
have four sepals, but no petals. Fruits have hooked tips that can latch on to passing animals, including humans. 

Jumpseed also spreads by rhizomes, underground stems that form patches of plants. Where the plants aren’t desired, this can be a problem, because they tend to persist even after pulling. The same is true for eastern jumpseed, an introduced plant. Once considered a variety P. virginiana called filiformis but now recognized as a separate species, Persicaria filiformis, it is beginning to develop a reputation as invasive because of its rhizomatous habit. It differs from P. virginiana in having pink to red flowers and often variegated leaves, characteristics that make it popular in the horticultural trade. Several cultivars of eastern jumpseed, such as ‘Painter’s Palette,’ ‘Lance Corporal,' and ‘Batwings,’ are offered for sale from some nurseries.

The last two cultivar names come from colorations on jumpseed’s leaves. In spring, the leaves are marked with maroon or dark green chevrons, upside down V’s that resemble military insignia or wings. The chevrons on Virginia jumpseed disappear by the time the plants flower, but those on eastern jumpseed leaves may persist.

Jumpseed has alternate leaves and hairy ocreas.
Notice the swollen nodes. 
Jumpseeds belong to the buckwheat or knotweed family, Polygonaceae (poly-gon-AY-see-ee). A typical trait of the family is a thin sheath called an ocrea (or ochrea) above each node. In formal terms, the sheath is described as scarious, meaning it is dry and membranous. The ocrea is formed from stipules that, sometime in the long history of knotweeds, fused to form a tube around the stem. 

Another trait that identifies this family is its knobby or swollen nodes. They resemble knees, if you use your imagination. Polygonaceae means “many knees.”


Maryland Invasive Species Council (Persicaria filiformis)

John Philip Baumgardt. How to Identify Flowering Plant Families: A Practical Guide for Horticulturists and Plant Lovers. Timber Press, 1982. 

Tuesday, July 18, 2023

Plant Profile: Michigan Lily


Michigan lily flowering in mid-July in Hennepin County, Minnesota.

This lone Michigan lily (Lilium michiganense), barely out of reach of the ditch mower and surrounded by invasive reed canary grass (Phalaris arundinacea), grows at the edge of a wetland. That’s typical for this native perennial, which is also found along streambanks and shores and in wet meadows, prairies, bogs and woodland edges and openings.

Michigan lily looks much like Turk’s cap lily (Lilium superbum), another native that grows in the same habitats farther south. In fact, some references call Lilium michiganense Turk’s cap lily, a mix-up that shows why scientific names are helpful. They may be tongue-twisters, but unlike common names, scientific names are usually the same no matter where you are (or what you’re reading), so there’s less confusion.

According to most references, this one is almost certainly Michigan lily. It’s 34 feet tall, well within the 3 to 6foot height typical of this species. Turk’s cap lily tends to grow taller, usually 57 feet.

Their flowers also differ, but the differences are subtle. Both species have umbels of nodding flowers with orange-red, dark-spotted tepals (similar petals and sepals) that are reflexed, bending back toward the base of the flower. Large stamens and a long pistil emerge from the center of the flowers and hang downward.

Umbels of Michigan lily flowers (left) and sets of whorled leaves on the stem (right).

In Michigan lilies the tips of the tepals are said to reach the base of the flower, but not much farther. In contrast, the tepals of Turk’s cap lily reach so far back they go beyond the base of the flower and may touch each other. In addition, their anthers, the pollen-bearing tips of the stamens, differ in length. According to several references, those of Michigan lily are never more than ½ inch long, whereas those of Turk’s cap lily are at least ½ inch long or longer.

If you don’t have a ruler handy, there are other differences to look for. If flower buds are present, look at their shapes. Michigan lily buds are more or less round in cross section, whereas Turk's cap lily buds are triangular. Open flowers also display differences. The pistil of Michigan lily is orange-red, whereas the pistil of Turk’s cap lily is greenish white to whitish orange. Looking deep into the flower, you’ll sometimes see a green, star-shaped center in Turk’s cap lily, but not in Michigan lily. 

Another look-alike is the introduced tiger lily, Lilium lancifolium, a garden favorite. It differs from both Michigan and Turk’s cap lilies in that it has alternate, not whorled, leaves, and small bulbs in the leaf axils.

Growing near this Michigan lily was yet another look-alike, Tawny day lily, Hemerocallis fulva. Also called ditch lily for its common habitat, it has orange-red flowers that open upward and have streaked but not spotted tepals. Day lilies have strap-shaped basal leaves but no leafy stems.

Tawny day lily flowers on leafless stems amid strap-shaped basal leaves. The flowers open upward, their red-orange tepals streaked but not spotted.

Michigan lily ranges throughout the upper Midwest and the Great Lakes region and less commonly farther east and south. In this region, it flowers in July. Pollinators are thought to be hummingbirds, butterflies and moths.

Michigan lily's range in North America (left) and the Upper Midwest (right). Maps from USDA Plants Database.


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