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Published In: Prodromus Systematis Naturalis Regni Vegetabilis 2: 329. 1825. (Prodr.) Name publication detailView in BotanicusView in Biodiversity Heritage Library
 

Project Name Data (Last Modified On 8/29/2017)
Acceptance : Accepted
Project Data     (Last Modified On 7/9/2009)
Status: Native

 

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Desmodium paniculatum (L.) DC. (tall tick trefoil)

Pl. 394 e, f; Map 1745

Stems 50–150 cm long, erect or ascending, sometimes arched, rarely spreading with an ascending tip, often branched, the median portion sparsely pubescent with appressed hairs or with scattered straight, spreading and/or hooked hairs, rarely completely glabrous or densely covered with straight, spreading and/or hooked hairs. Petioles of the median leaves 1–5 cm long, only slightly reduced toward the stem tip, those of the upper leaves 1–5 cm long. Stipules 2–6 mm long, 0.3–1.0 mm wide, narrowly triangular, tapered to a sharply pointed tip, at maturity brown and appressed, shed early or less commonly semipersistent. Leaflets flat or nearly so, the undersurface sparsely pubescent with straight, appressed or rarely spreading hairs, the network of raised veins relatively inconspicuous. Central leaflet (1.5–)3.5–8.0(–10.0) cm long, (0.2–)0.5–2.5 cm wide (generally 3–8 times as long as wide), narrowly oblong, or lanceolate, the tip bluntly to sharply pointed. Lateral leaflets (1.5–)2.5–7.0(–8.0) cm long, (0.2–)0.5–2.0 cm wide. Stipels 1–4 mm long. Inflorescences terminal and from the upper leaf axils, branched, the axis with hooked and sometimes straight, spreading hairs. Primary bracts, 1.5–3.0 mm long, lanceolate, tapered to a sharply pointed tip, mostly shed early. Secondary bracts 1.0–1.5 mm long, linear or hairlike, shed early or semipersistent. Flower stalks 4–11 mm long. Calyces green, with scattered appressed hairs and dense very short hairs, the tube 1.0–1.5 mm long, the lobes 2–3 mm long. Corollas 5–8 mm long, pink, often fading to bluish purple or blue, the nectar guides green and white outlined in purple. Fruits straight in outline, the stalklike base 2–5 mm long (extending past the persistent calyx), consisting of (1–)4 or 5 segments, each 5–7 mm long and 3–5 mm wide, bluntly angled to more or less rounded on the upper margin, bluntly angled on the lower margin, with deeper indentation below (rarely rounded below and with nearly equal indentations above and below), the margins and faces uniformly covered with hooked hairs. 2n=22. July–September.

Scattered to common nearly throughout the state (eastern U.S. west to Nebraska and Texas; Canada). Bottomland forests, openings and edges of mesic to dry upland forests, tops of bluffs, glades, savannas, upland prairies, banks of streams and rivers, edges of marshes and fens, and margins of ponds and lakes; also old fields, pastures, levees, railroads, and roadsides.

This species, along with the broader-leafleted D. perplexum and D. glabellum, presents one of the most difficult complexes in the Missouri flora. Although many specimens can be readily classified as one of the three species, a substantial proportion seems to bridge the morphological gaps between them (Isely, 1983b). Isely (1990) suggested that plants of intermediate morphology might represent hybrids between D. paniculatum and one or both of these other two species. Some other authors have chosen to combine all three taxa into D. paniculatum and to recognize only two varieties: the nominate variety with narrow leaflets and less conspicuous pubescence; and the other variety with broader leaflets and conspicuous pubescence (Steyermark, 1963). The latter has been called var. dillenii (Darl.) Isely and encompasses both D. glabellum and D. perplexum. The present recognition of three species is tentative and further research is needed. Adding to the complexity of the group is a tendency for some collections, especially from northeastern Missouri, to have larger flowers, longer stipules, and rounded fruit segments, somewhat similar to those of D. canadense. Isely (1990) noted the existence in the Southeast of occasional plants resembling D. paniculatum, but with very short petioles. He suggested that such plants might represent hybrids between this species and D. ciliare. Such plants eventually may be found in Missouri, as the two putative parents frequently grow in proximity. Evidence for hybridization with D. rotundifolium is discussed under that species.

 


 

 
 
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