Ragworts (Groundsels)

Deer, rabbits, livestock, and other herbivorous mammals tend to avoid eating ragworts due to toxic pyrrolizidine alkaloid chemicals in the plants’ tissues.

A wide variety of bees, flies, beetles, and other insects visit the flowers for nectar and pollen.

One of Missouri’s rarer butterflies, the northern metalmark (Calephelis borealis), uses round-leaved groundsel, possibly also golden ragwort, and perhaps some types of fleabane daisies as caterpillar food plants.

• The northern metalmark is a species of conservation concern in Missouri. It occurs only in small, localized populations and is rare, declining, threatened, or endangered throughout its range (our other metalmark species is the swamp metalmark).

The white-crossed seed bug (Neacoryphus bicrucis) is a colorful insect that feeds on ragworts. Apparently it can sequester the plant’s toxic chemicals in its tissues, which gives it protection from predators. The bug’s bright colors probably serve as warning coloration.

An attractive geometrid moth called “the gem” (Orthonama obstipata) uses ragworts and several other kinds of plants as caterpillar food plants. It is found worldwide. It may not be able to survive Missouri’s cold winters, but each year it recolonizes our state from populations that survived winter to our south.

Taxonomy: Missouri’s species in genus Packera used to be grouped with about 3,000 other species into a gigantic genus Senecio. Today, even with the packeras and several other groups split away, Senecio is still a huge genus, with more than 1,200 species, mostly in the Old World. Only two species of true senecios have been recorded in Missouri, both introduced/nonnative and uncommon.

Below, Missouri's seven Packera species are listed roughly in order by how widely distributed or common they are in the state.

• Round-leaved groundsel, or roundleaf ragwort (Packera obovata), has mostly basal leaves whose blades are rounded to spoon-shaped, toothed, with the leafy tissue conspicuously continued into the leaf stem. The stem leaves are few, sessile (stalkless), often deeply lobed. The flowerheads are terminal on a long stalk with few leaves. The ray flowers are few, looking somewhat ragged. Perennial, to 2 feet tall; usually grows in colonies. Blooms April–June. Rich or rocky woods, bases of bluffs, on slopes, mostly south of the Missouri River.
• Prairie ragwort (Packera plattensis) has mostly basal leaves; the lowest of these have paddle-shaped blades with a pointed tip and have long petioles (leaf stems); the base of the blade tapers or is abruptly contracted where it joins the petiole. The lowest stem leaves are deeply pinnately lobed or appear pinnately compound. The stem leaves are few, sessile (clasping), and short. The basal and stem leaves are sharply toothed. Usually a perennial, to 2 feet tall; it starts out a hairy plant with white, cobwebby hairs; these often wear away by flowering time except for patches at the leaf bases or flower cluster branch points. The flowerheads are few to many, terminal, with few ray flowers. Blooms May–June. Prairies, dry, open uplands, scattered statewide. To distinguish it from the similar, but less widespread northern ragwort, see that species listed below.
• Golden ragwort (Packera aurea) has mostly basal leaves whose blades are heart-shaped, with a pointed tip, crenate (scalloped or round-toothed) to coarsely toothed, on very long petioles (leaf stems). The stem leaves are very few, small, and pinnately lobed. Frequently the plant has a purplish main stem. Perennial, to 2½ feet tall. The flowerheads are numerous and similar to those of Packera obovata. Blooms April–June. Low, moist areas, including near spring outlets, generally south of the Missouri River. To distinguish it from the similar, but less widespread western golden ragwort, see that species listed below.
• Butterweed (Packera glabella) usually has no basal leaves at flowering time; the stem leaves, however, are largest at the base of the plant and get gradually smaller up the stem. The blades are deeply pinnately lobed, with toothed margins. Usually an annual with fibrous roots, lacking rhizomes or stolons, to 3 feet tall, unbranched, smooth, without hairs, growing in colonies, at times covering acres of floodplain. The stems are often inflated or hollow. The flowers are abundant, with rich golden heads with few ray flowers. Blooms April–June. Floodplains of the Mississippi and Missouri rivers and their tributaries, in southeastern and east-central Missouri. From a distance, colonies of butterweed may be misidentified as colonies of yellow rocket (a type of mustard).
• Northern ragwort, or balsam groundsel (Packera paupercula), is scattered in Missouri, mostly in the northern half of the state, and occurs in upland prairies, loess hill prairies, openings of mesic to dry upland forests, ledges of bluffs, and rarely in bottomland forests; also on pastures, railroads, and roadsides. A perennial, blooming April–August. It is closely related to prairie ragwort, which also lives in open habitats, and the two can be difficult to tell apart. Northern ragwort tends to lose more of its hair as it matures, while prairie ragwort retains more. Northern ragwort tends more commonly to produce short rhizomes with few stolons (runners), while prairie ragwort more commonly produces slender stolons (runners). The leaf blades of northern ragwort are usually more than 3 times as long as they are wide, while those of prairie ragwort are less than 3 times as long as wide.
• Western golden ragwort, or falsegold groundsel (Packera pseudaurea), is scattered in western and northern Missouri and occurs in bottomland prairies and forests, mesic upland forests in ravines, banks of streams and rivers, and occasionally ledges of bluffs; also in pastures and ditches. A perennial, blooming April–June. This species is closely related to golden ragwort, and the two can be difficult to tell apart. Western golden ragwort has basal leaf blades that are oblong-ovate to broadly lance-shaped, and usually truncate (squared-off) or only shallowly cordate at the base; also, it tends to have ascending leaves, and its involucral bracts frequently have little purplish color. Meanwhile, golden ragwort has basal leaf blades that are rounder (oblong-ovate to nearly circular), truncate or cordate (heart-shaped) at the base, with at least some deeply cordate; also, its leaves tend to droop and spread, and its involucral bracts often are noticeably purple, at least toward the tip. The Missouri representatives of western golden ragwort are variety semicordata.
• Woolly ragwort, or hairy groundsel (Packera tomentosa), is known in our state from only a single historical collection in the late 1800s from a riverbank in southwestern Missouri (Eagle Rock, Barry County). Its overall range is mostly in the southeastern United States, especially the coastal plain, ranging as far west as Oklahoma and Texas. A perennial, blooming March–May. This ragwort is more or less evenly and persistently covered with dense, felty (tomentose) hairs (though the leaf blades, especially the upper surfaces, may be nearly hairless by flowering time). It is a Missouri species of conservation concern; there is still some hope it might be rediscovered in our state.

Two species in the closely related genus Senecio (also called ragworts and groundsels) have been recorded in Missouri; they differ from our Packera species by having the leaves all sessile (stalkless), while our native packeras have at least the basal leaves with a long, well-defined leaf stem. Both of the senecios are nonnative annuals and are uncommon to rare in Missouri:

• Common groundsel (Senecio vulgaris), native to Eurasia, is uncommon and sporadic in Missouri, mostly recorded from the St. Louis metro region. It sometimes spreads as weeds in bedding plants and occurs in greenhouses and gardens, along railroads, and in other open, disturbed areas. It lacks petal-like ray flowers, the leaves are mostly pinnately lobed, and it grows about 2 feet tall.
• Texas groundsel or Texas ragwort (Senecio ampullaceus), native to Texas, has been recorded from railroads in the St. Louis area. Leaves start off with cobwebby hairs; at maturity, they are smooth. Upper leaves on the stem are sessile (clasping), unlobed, and shallowly toothed.