Verbena L.

Tutin, T. G., Heywood, V. H., Burges, N. A., Moore, D. M., Valentine, D. H., Walters, S. M. & Webb, D. A., 1972, Flora Europaea. Volume 3. Diapensiacea to Myoporaceae, Cambridge: Cambridge University Press : 122-123

3. Verbena L. 3

Annual or perennial herbs or small shrubs. Leaves opposite or rarely in whorls of 3. Flowers in bracteate spikes, usually arranged in panicles or corymbs. Calyx tubular, 5-ribbed and unequally 5-dentate. Corolla hypocrateriform, weakly 2-lipped, with obtuse or emarginate lobes. Stamens inserted at about the middle of the corolla-tube, included. Stigma unequally 2-lobed. Fruit separating at maturity into 4 nutlets.

Several American species, as well as their hybrids, are grown in European gardens and sometimes escape. Among them, V. canadensis (L.) Britton , Mem. Torrey Bot. Club 5: 276 (1894) ( K aubletia Jacq. ), from E. North America, and V. peruviana (L.) Druce , Rep. Bot. Exch. Club Brit. Is. 3: 425 (1914) ( V. chamaedryfolia Juss. ), from South America, are locally naturalized in Germany and the latter also in E. France (near Strasbourg). V. canadensis has pinnatipartite to 3-fid leaves and shortly pedunculate spikes elongating in fruit, with crowded, large and showy flowers in shades of blue, purple or white. V. peruviana has crenate to incise-dentate leaves and long-pedunculate spikes with crowded, large and showy, bright scarlet to pink flowers; both are perennial herbs.

1 Leaves dentate to incise-serrate, sessile, amplexicaul; spikes very dense

2 Bracts distinctly longer than calyx; spikes pedunculate, not crowded 1. rigida 2 Bracts equalling or shorter than calyx; spikes mostly sessile and crowded 2. bonariensis 1 At least the lower leaves deeply incised to 1- to 2-pinnatisect, petiolate; spikes slender, becoming lax

3 Stem scabrid on the angles, usually erect; fruiting spikes 10-25 cm 3. officinalis 3 Stem strigulose, usually procumbent; fruiting spikes up to

8 cm 4. supina