Medicago

Medicago L.

Medicago, as currently understood (see Small 1987, Small & al. 1987, Small & Jomphe 1989, Mabberley 2008), is an Old World genus of 83 species that are mostly native to Europe and the Mediterranean area. Most species of Trigonella and Medicago are morphologically well delimited on the basis of their pods (respectively uncoiled versus coiled) but a number of species is obviously intermediate. Small (1987) proved that ca. 23 species that were traditionally placed in Trigonella in fact are more closely related to Medicago (the so-called “medicagoid” trigonellas). His point of view has become widely accepted (Mabberley 2008; see however Hedge & Sales 2000) and also confirmed by molecular data (Bena 2001); it is applied here as well. In Medicago s.l. (incl. Trigonella p.p.) keels and wings are tightly interconnected whereas in Trigonella s.str. keels and wings are loosely or not at all interconnected (Small l.c.).

The residence status of some of the Belgian representatives of the genus is critical (compare Lawalrée 1961 and Lambinon & al. 2004). At present four species are believed to be native: Medicago arabica (L.) Huds., M. falcata L., M. lupulina L. and M. minima (L.) L. (Lambinon & al. l.c.) but only M. lupulina is doubtlessly native. The others are probably only locally native or nowadays more regularly seen as introductions in non-natural habitats.

Several species of the genus Medicago are economically important. Medicago sativa (alfalfa) is widely cultivated for fodder or as green manure. Rather few species are cultivated as ornamentals (probably none in Belgium or only very rarely so) and some are weeds of arable land (and therefore regularly occur as grain aliens). Species of Medicago formerly were among the most characteristic wool aliens in the valley of river Vesdre, their spiny pods easily adhering in the imported sheep wool.

Medicago is a difficult genus and determination of species often requires some experience. However, at present, only few species are more or less regularly introduced (apart from Medicago sativa: M. polymorpha, M. scutellata and M. tuberculata). These species are relatively easily told apart (see key and text). In most cases mature fruits are necessary for an accurate determination.

An up-to-date and very extensive, monographic overview of the entire genus (including keys and illustrations) is provided by Small (2011).

The Belgian collections of Medicago were critically revised by van Ooststroom & Reichgelt (1957, 1958).

1. Corolla blue to violet. Perennial === 7. Medicago sativa

1. Corolla yellow [1]. Annuals or perennials === 2

2. Pod uncoiled, straight, falcate or reniform === 3

2. Pod spiraled through more than one coil === 5

3. Pod reniform, as long as wide (at most 3 mm long), with a single seed. Stems procumbent to ascending (native) === M. lupulina

3. Pod straight to falcate, much longer than wide (more than 3 mm long), with several seeds. Plant erect === 4

4. Inflorescence 1-2(-3) flowered. Pod terete, (30-) 40-100 mm long. Annual === 2. M. monantha subsp. noeana

4. Inflorescence 5-40 flowered. Pod distinctly flattened, 5-8 mm long. Perennial (native) === M. falcata

5. Coils of pod distinctly imbricate (each coil included in adjacent coil), always spineless. Entire plant densely glandular hairy === 8. M. scutellata

5. Coils more or less flat, spiny or spineless. Plant glabrous or pubescent, never densely glandular hairy (occasionally with a scattered glandular hair) === 6

6. Mature seeds papillate. Coils spineless, papery, 10-20 mm across === 4. M. orbicularis

6. Mature seeds smooth. Coils spiny or rarely (almost) spineless, usually much less wide === 7

7. Coils very tightly appressed (coils cannot be separated by hand without probability of injury). Spines very hard, distinctly broadened and terete at base and difficult to bend === 8

7. Coils loosely appressed (easily separated). Spines soft and flexible, not much broadened at base, always with a distinct groove === 9

8. Marginal part of coil veinless (best seen in young pods). Leaflets glabrous above === 3. M. murex

8. Coils without a well-developed veinless area. Leaflets densely hairy above === 9. M. truncatula

9. Edge of pod with four distinct ridges. Leaflets nearly always with a black spot. Plant often with multicellular hairs (native) === M. arabica

9. Edge of pod without or with fewer ridges. Leaflets without black spots. Multicellular hairs absent === 10

10. Stipules entire or merely dentate, not dissected. Leaflets densely hairy above (native) === M. minima

10. Stipules dissected. Leaflets glabrous above === 11

11. Corolla ca. 2,5 mm long. Inflorescence 1-2 flowered. Back of the coil relatively wide (ca. 0,5 mm), smooth. Peduncle always shorter than the subtending leaf === 6. M. praecox

11. Corolla 3-8 mm long. Inflorescence 1-9 flowered. Back of the coil narrower, ridged. Peduncle as long as to longer than subtending leaf === 12

12. Pedicels usually distinctly aristate, at least in some flowers (continuation of the pedicel beyond insertion of the flower). Usually at least some leaflets laciniate. Coils very loosely appressed (space between the coils evident). Pod ca. 2,5-5 mm across === 1. M. laciniata

12. Pedicels not aristate. Leaflets dentate near apex, never laciniate. Coils more tightly appressed (space between coils nearly invisible). Pod 4-10 mm across === 5. M. polymorpha

Additional aliens: Medicago carstiensis Wulfen (SC and SE-Eur., seed alien), M. doliata Carmign. (Medit., wool alien), M. fischeriana (Seringe) Trautv. (syn.: Trigonella fischeriana Seringe) (Crimea, SW-Asia, wool alien), M. intertexta (L.) Mill. subsp. ciliaris (L.) Ponert (syn.: M. ciliaris (L.) All.) (Medit., wool alien), M. intertexta subsp. intertexta (Medit., seed alien), M.cf. littoralis Rohde ex Loisel. (Medit., vector unknown), M. monantha (C.A. Mey.) Trautv. subsp. incisa (Benth.) Verloove et Lambinon (syn.: Trigonella incisa Benth., T. monantha C.A. Mey. subsp. incisa (Benth.) Ali (SW-As., wool and grain alien), M. rigidula (L.) All. (Medit., wool alien), M. tornata (L.) Mill. subsp. helix (Willd.) Ooststr. et Reichg. (syn.: M. italica (Mill.) Fiori) (Medit., vector unknown) and M. turbinata (L.) All. (Medit., grain alien?).