Asarina

''Asarina'' is a flowering plant genus of only one species, ''Asarina procumbens Mill.'' Search for "Asarina", the trailing snapdragon, which is native to France and Spain and introduced in Germany, Switzerland, Austria and Hungary. Originally placed in the Scrophulariaceae (figwort family), the genus has more recently been moved to the Plantaginaceae (plantain family). Species from North America formerly placed in the genus ''Asarina'' are now placed in '' Holmgrenanthe'', ''Lophospermum'', '' Mabrya'' and ''Maurandya'', as well as '' Neogaerrhinum''. ''Asarina'' is now regarded as exclusively an Old World genus.

Description

The single remaining species of the now monotypic genus, ''A. procumbens'' is a foetid, strongly pubescent, viscid subshrub of trailing/mat-forming habit reaching a height of only 10-20cm. The somewhat woody main stems give rise to lax creeping/cascading stems bearing opposite, long-petioled, hairy, lobed, reniform-to-cordate leaves with crenate and often red-tinged margins. Flowers solitary or in short racemes of only two or three, fragrant, bumblebee-pollinated, borne in the leaf axils. Corolla cream-coloured, somewhat resembling that of Antirrhinum, the tube bearing faint violet striations, the upper part divided into two keel-like lips, the lower bearing paired inflated lobes, concealing the corolla tube, with a three-lobed margin; pistil violet, persistent, stamens four. Base of corolla bearing (starting behind inflated lobes and extending into corolla throat) a dense mat or beard of deep yellow trichomes. Calyx tubular, five-toothed, densely hairy. Peduncle narrow where joined to stem, thickening greatly to junction with fruiting calyx, reflexed so as to lie parallel to capsule. Fruit a dry capsule, glabrous, subglobose, shorter than the calyx and dehiscing at the apex by two openings separating three valves, the central valve bearing the persistent withered pistil. Seeds small, brownish-buff, roughly conical, testa finely incised with deep sinuous furrows. Seed distribution is by epizoochory, the sticky fruiting calyces becoming attached to the fur of mammals or the feathers of birds, allowing the small seeds to trickle from the dry, open capsules.http://erick.dronnet.free.fr/belles_fleurs_de_france/asarina_procumbens1.htm Retrieved at 11.07 on Thursday 9/6/22.

Endangered habitat

''A. procumbens'' is a semi-evergreen alpine chasmophyte, favouring partial shade, its preferred habitat being crevices in silica-rich, non-sedimentary rocks. This type of habitat - "Mediterranean siliceous inland cliff" - is designated by endangered habitat code H3.1d by the European Red List of Habitats. The term siliceous cliffs (in this context) refers to those which are composed chiefly of quartz-rich rocks (making them of an acidic character) of either igneous type, such as granite, diorite and andesite, or metamorphic type, such as gneiss, slate, schist and quartzite. Low-altitude cliffs of this type - as favoured by ''A. procumbens'' - are more affected by human disturbances than high mountain cliffs, as the latter often occur within nature reserves and other protected areas. Cliffs at low altitudes, by contrast, are susceptible to a wide variety of threats including the shoring-up of cliffs over roads and railway lines, sport and leisure activities -particularly rock-climbing - and, at lower elevations, mining, quarrying and invasive/alien plants.
In the French part of its range ''A. procumbens'' is seldom to be found growing at altitudes below 400m, with an upper limit of some 1800m.

Distribution in France and Spain

''A. procumbens'' is not a common species in the French part of its range, even having protected status in the Auvergne region. Its strongholds in France comprise the Pyrénées-Orientales (taking in the Franco-Catalan area of historic Rousillon) and the Massif central - notably the Cévennes. In Spain the plant is native to the Pyrenean region, but may be found naturalised elsewhere.

Cultivation

''A. procumbens'' grows best in somewhat dry partial shade. Soil: well-drained, sandy/gravelly, humus-rich, moderately moist: dislikes excessive winter wetness. Blooms most profusely in climates in which summers are not excessively hot. Pollinated by bumblebees. Plant is evergreen in mild climates, although may be killed outright by heavy frost, in which case may be propagated afresh: self-seeds readily. Uses: trailing alpine or ground cover. Thrives and increases rapidly as a container plant. Not usually invasive in gardens, though one report of aggressive growth from southeastern U.S.A. Rainy Side Gardeners https://www.rainyside.com/plant_gallery/perennials/Asarina_procumbens.html Retrieved at 9.37 on Tuesday 14/6/22. Pruning: not usually needed, though may be cut back in autumn if foliage is spent or untidy. Hardiness zone: U.K. H3. USDA zones 8,9 & 10.

Weed status in Australia

''A. procumbens'' has escaped from cultivation to become an attractive (and not, at present, invasive) weed in the inner suburbs of the Australian city of Melbourne, managing to grow in such harsh urban habitats as cracks in the mortar of brick walls and kerbstones and the juncture between brick walls and tarmac.
Such weedy populations are short-lived and do not produce abundant seed, because of the current absence of bumblebees from the Australian insect fauna (in its native habitats in France and Spain Asarina is buzz-pollinated by bumblebee species): the Australian native bees and introduced honeybees of Melbourne find Asarina flowers resistant to their attempts at pollination. This situation is, however, likely to change for the worse, should bumblebee species already present in neighbouring Tasmania cross the Bass Strait, in which case bumblebee-pollinated species - such as Asarina - hitherto considered "safe" (i.e. non-invasive) garden plants in the state of Victoria - would rapidly become invasive due to increased production of viable seed. Michael Cook hypothesises that the Asarina colonies currently observable in suburban Melbourne may be more the result of wind-blown drift of packaged seed sown by local gardeners than of the setting of seed by garden plants and plants maintaining a foothold as weeds. Michael David Cook, Weeds of Melbourne https://weedsofmelbourne.org/trailing-snapdragon-asarina-procumbens Retrieved at 10.54 on Sunday 12/6/22.

Species reassigned to other genera

At one time placed in ''Asarina'':

*''Asarina acerifolia'' (Pennell) Pennell = '' Mabrya acerifolia'' (Pennell) Elisens
*''Asarina antirrhiniflora'' (Humb. & Bonpl. ex Willd.) Pennell = '' Maurandya antirrhiniflora'' Humb. & Bonpl. ex Willd.
*''Asarina barclayana'' (Lindl.) Pennell = '' Maurandya barclayana'' Lindl.
*''Asarina erubescens'' (D.Don) Pennell = '' Lophospermum erubescens'' D.Don
*''Asarina filipes'' (A.Gray) Pennell = '' Neogaerrhinum filipes'' (A.Gray) Rothm.
*''Asarina flaviflora'' (I.M.Johnst.) Pennell = '' Mabrya flaviflora'' (I.M.Johnst.) D.A.Sutton
*''Asarina geniculata'' (B.L.Rob. & Fernald) Pennell = '' Mabrya geniculata'' (B.L.Rob. & Fernald) Elisens
*''Asarina hirsuta'' Pennell = '' Mabrya erecta'' (Hemsley) Elisens
*''Asarina lophospermum'' (L.H.Bailey) Pennell = '' Lophospermum scandens'' D.Don
*''Asarina petrophila'' (Coville & C.V. Morton) Pennell = '' Holmgrenanthe petrophila'' ( Coville & C.V.Morton) Elisens
*''Asarina purpusii'' (Brandegee) Pennell = '' Lophospermum purpusii'' (Brandegee) Rothm.
*''Asarina rosei'' (Munz) Pennell = '' Mabrya rosei'' (Munz) Elisens
*''Asarina scandens'' (Cav.) Pennell = '' Maurandya scandens'' (Cav.) Pers.
*''Asarina stricta'' (Hook. & Arn.) Pennell = '' Neogaerrhinum strictum'' (Hook. & Arn.) Rothm.
*''Asarina wislizeni'' (Engelm. ex A.Gray) Pennell = '' Maurandya wislizeni'' Engelm. ex A.Gray

Gallery

File:Curtis's botanical magazine (10594334356).jpg, Colour plate from Curtis’s Botanical Magazine 1806
File:Asarina procumbens church wall Paxton Scottish Borders.jpg, Specimen growing out of crevices in front wall of church grounds, Paxton, Scottish Borders
File:Asarina procumbens cascading down wall beside Paxton church gatepost.jpg, Detail of cascading stems of church gate specimen
File:Asarina procumbens woody growth producing cascade of flowering stems.jpg, Woody growth at top of specimen producing cascade of flowering stems
File:Asarina procumbens woody growth mid shot.jpg, Mid-shot of woody growth and cascade of flowering stems
File:Asarina procumbens detail of woody stems.jpg, Detail of woody stems growing out of crevice in church gate wall.
File:Asarina procumbens growing between wall and tarmac.jpg, Outlying plant growing between wall and tarmac at pavement level
File:Asarina procumbens flowering shoot with buds and senescent flowers.jpg, Flowering shoot baring buds at varying stages of development and senescent flowers
File:Asarina procumbens slipper-shaped flower buds.jpg, Paired, slipper-shaped flower buds borne at a leaf node
File:Asarina procumbens single flower viewed from above.jpg, Single flower, viewed from above, revealing purple dorsal stripe
File:Asarina procumbens flower pollinated by Bombus hortorum.jpg, Close-up of flower of Paxton specimen being pollinated by garden bumblebee,
File:Asarina procumbens and pollen-covered Bombus hortorum.jpg, Pollen-covered garden bumblebee, newly emerged from flower
File:Asarina procumbens, paired seed capsules with reflexed peduncles.jpg, Paired seed capsules, showing distinctive reflexed peduncles, borne at a node with paired opposite leaves
File:Asarina procumbens single ripening seed capsule greatly enlarged.jpg, Single, ripening seed capsule, greatly enlarged: contrast between pubescent peduncle and calyx and glabrous capsule
File:Asarina procumbens single capsule showing dehiscence by three valves.jpg, Ripe, buff seed capsule (showing reflexed peduncle) dehiscing by three valves to reveal brain-like seeds
File:Asarina procumbens detached, imperfectly dehisced, ripe seed capsule and seeds.jpg, Detached, imperfectly dehisced, ripe seed capsule with shed seeds
File:Asarina procumbens detached three-valved capsule with ripe seeds.jpg, Perfectly dehisced capsule detached to show three valves, central one bearing dry, persistent pistil

References

* Ellison, Don (1999) Cultivated Plants of the World. London: New Holland (1st ed.: Brisbane: Flora Publications International, 1995)
* Graf, Alfred Byrd (1986) Tropica: color cyclopedia of exotic plants and trees for warm-region horticulture—in cool climate the summer garden or sheltered indoors; 3rd ed. East Rutherford, N.J.: Roehrs Co
* Lord, Tony (2003) Flora : The Gardener's Bible : More than 20,000 garden plants from around the world. London: Cassell.

Botanica Sistematica

{{Taxonbar, from=Q1532290

Plantaginaceae
Plantaginaceae genera
Monotypic Lamiales genera
Taxa named by Philip Miller