ARUM ORIENTALE

PROTOLOGUE: Arum orientale , published in Flora Taurico-Caucasica 2: 407 (1808). The protologue is reproduced below.

DISTRIBUTION: EC. Europe to W. Caucasus: Albania, Armenia, Austria, Azerbaijan, Bosnia and Herzegovina, Bulgaria, Croatia, Czechia, Georgia-GE, Greece, Hungary, Israel, Jordan, Kosovo, Krym, Lebanon, Montenegro, North Caucasus, North Macedonia, Palestinian Territories, Poland, Romania, Serbia, Slovakia, Slovenia, South European Russia, Syria, Türkiye, Türkiye-in-Europe, Ukraine.

DISTRIBUTION NOTE: iNaturalist: Blagoevgrad, Giurgiu, Mehedinți, Plovdiv.

SPECIES DESCRIPTION:

Tuberous herb sprouting in mid-autumn to late autumn from a discoid, horizontally orientated tuber 4—6 cm across, 2—2.5 cm thick. Petiole terete, 18-46 cm long, 3—7 mm wide, deep green, usually stained with purple, especially towards the base. Leaf-blade broadly hastate, apex obtuse to subacute, 8.5-25 cm long, 5.5—17 cm wide, deep green

INFLORESCENCE:

Inflorescence smelling moderately of horse-dung (subsp. orientale, subsp. longispathum) or sweet, fermenting (subsp. sintenisii). Peduncle much shorter than to almost equalling the leaves, terete, 11-19 cm long, 3-4 mm wide, deep green, sometimes stained with purple. Spathe 14.5—30 cm long; spathe-tube oblong-cylindric, 2.5—5.5 cm long, 1.5-2.5 cm wide, constricted apically, exterior mid-green with dull purple staining towards the margin and apex, fading to greenish white at the base, interior greenish white below, purple above; spathe-limb ovate to ovate-lanceolate, 12—24.5 cm long, 4—7 cm wide, erect at first but the apex soon flopping forwards, acute to rather bluntly acute, externally pale to mid-green, heavily to moderately stained purple, median vein pale green, internally similarly coloured, but with much heavier purple staining, apex mid-green. Spadix ⅓–½ as long as the spathe-limb, 5.5—16 cm in total length; appendix slender-clavate to cylindric, long-stipitate or stalkless, 3.5—13: cm long, 3.6-6.5 cm wide, dull mid-purple, stipe when present generally paler. Staminodes in c. 2 whorls forming a zone 4—7.5 mm long, yellow, flushed with purple; bases conic, + smooth, yellow. Interstices: upper 2.5-4 mm long, ° sparsely grooved, minutely verrucate, yellow; lower + absent. Staminate flowers in an quadrate zone 2-5.5 mm long, 3-5 mm wide; anthers yellow with purple tips, connectives yellow. Pistillodes in 3 or 4 whorls forming a zone 3-7 mm long; bristles filiform, flexuous, 2.5-6 mm long, yellow, flushed with purple; bases compressed conic, smooth, deep yellow. Pistillate flowers in a globose-cylindric cluster, 4.5—20 mm long; ovaries globose, 1.5-2 mm long, dull oblive-green, stained with purple apically; stigma papillose, green. Fruiting head cylindric, 4—5.6 cm long, 2-2.5 cm wide; berries oblong, 5~10 mm long, 3.5-5 mm wide

ECOLOGY:

sea-level to 950 m; altitude: 0-950 m

DISTRIBUTION MAPS:

ETYMOLOGY:

Latin, “eastern”, for its range east of the main European species.

NOTES:

1. The inflorescence is carried below the foliage, and smells of cattle dung and urine.⁵

2. Two taxa Boyce treated in 1993 as subspecies of this species were raised to species in 2006: Arum longispathum and Arum sintenisii.⁵

3. In pot culture, seedlings of the group of species centered on Arum orientale (including Arum sintenisii, Arum elongatum, Arum apulum, Arum nigrum and Arum gratum) can make tubers the size of a Brazil nut by the end of the first season and flowering plants within three years, if they are fed regularly and the whole pot of seedlings is moved up, without disturbing the root ball, into a larger pot with fresh compost below and around it as soon as roots show at the drainage holes.¹²

REFERENCES:

1. Plants of the World Online, Royal Botanic Gardens, Kew — Arum orientale

2. Flora Taurico-Caucasica 2: 407 (1808) — protologue.

3. iNaturalist: Arum orientale

4. Boyce, P.C. 1993. The Genus Arum: a Kew Magazine Monograph. Royal Botanic Gardens, Kew.

5. Boyce, P.C. 2006. Arum – a decade of change. Aroideana 29: 132–137.

6. Albre et al. 2003. Pollination ecology of Arum italicum (Araceae). Botanical Journal of the Linnean Society.

7. Diaz et al. 2006. The effectiveness of some mechanisms of reproductive isolation in Arum maculatum and A. italicum (Araceae). Botanical Journal of the Linnean Society.

8. Chartier et al. 2013. Geographical variations of odour and pollinators, and test for local adaptation by reciprocal transplant of two European Arum species. Functional Ecology.

9. 2006. Studies on the Genus Arum (Araceae).

10. Gibernau et al 2003. Arum Pollen longevity & viability.

11. Croat T.B 1989. Ecology and Life Forms of Araceae a Follow-up.

12. Aroid-L mailing list, Peter Boyce, January 5th, 1998

Additional photos by Alan Galloway, via the International Aroid Society

Additional photos from iNaturalist by Alexey Zyryanov, SteveM4560, Алена Ручка, Мария, Шильников Дмитрий Сергеевич, Mirko Ubović, Théo Philippe, Alexandr, demina-masha, Julia V. Shner, aleksandrabrusova, aleksandrzubar, Aleksei Baushev, Alexandra, Elena Kirichok, lullula-m, Max Kindler and Богданович Светлана