Note #13: Draft Key to Section Otidia

The following is a short key to the section Otidia of the genus Pelargonium. This is a draft key and is in the process of testing. The characters should be taken to be representative of adult plants or at least a few years of age. For plants in cultivation, the key should be used with caution, although the characters have genearlly be chosen such that they are not too plastic, as often happens in cultivation and has been the source of much confusion.

Please click the hyperlinks provided in the key for distribution maps, photographs etc.

Please also note that there are known populations of natural hybrids between subspecies of carnosum, as well as between parviflorum, carnosum and laxum. These may be therefore difficult to determine. Hybridisation in cultivation is frequent as the plants are easily cross-fertilised by bees also in the Northern hemisphere.

P. dasycaule is treated as an insufficiently known taxon, following the discussion available here.

Feedback would be hugely appreciated if you notice inconsistencies or lack of clarity. Please use the comment section below.

1	Stamens facing sharply downwards, posterior petals sharply curved backwards	2
	Stamens facing forwards, posterior petals curved at 90 deg or gently curved backwards or sharply curved back at the tip only	4
2	Stems thick (up to 4cm), tubers or thickened roots absent	keeromsbergense
	Stems thinner (<2cm), with tubers or thickened roots	3
3	Side tubers absent, stems >8mm thick, lamina margin sharply and deeply dentate	laxum ssp laxum
	With side tubers, stems <8mm thick, lamina margin entire or crenate	laxum ssp karooicum
4	Petals shorter than or equal in length to sepals	5
	Petals much longer than sepals	11
5	Hypocotyl develops into a round to irregularly shaped caudex (not an elongated taproot), seasonal stems <5mm thick, annual growth >10cm	pachypodium
	Stems thicker than 5mm, annual growth <10cm, mostly much less	6
6	Stems thin (5-10mm)	7
	Stems thicker than 10mm	8
7	Plants with several tubers connected by thin roots, flowers scented	albersii
	Plants with a thick, long taproot, flowers not scented	parviflorum ssp karasbergense
8	Posterior petals tennis racket-like, as long as sepals, white or pink, without markings	parviflorum ssp rotundipetalum
	Petals yellow, white or pink, with or without markings, posterior petals not tennis racket-like	9
9	Plants with side tubers	parviflorum ssp tuberculum
	Plants with a thick main root, without side tubers	10
10	Pseudo-umbels with up to 15 flowers, petals mostly cream-yellow or pink	parviflorum ssp parviflorum
	Pseudo-umbels with up to 30 flowers, petals intensively yellow	brevipetalum
11	Leaves simple to shalowly lobed, base cuneate, margin undulate to crenate	klinghardtense
	Leaves different, mostly pinnate or lobed to rachis	12
12	Inflorescence multi-flowered, taller than 10cm	13
	Inflorescence few-flowered, up to 10 flowers (can be more in cultivation), not taller than 10cm	19
13	Pedicel shorter than nectar tube	14
	Pedicel longer than nectar tube	16
14	Pedicel only a few mm long, barely visible in a very compact flowering pseudo-umbel, inflorescence maturing from the perimeter towards the centre	polycephalum
	Pedicel longer and visible in a flowering pseudo-umbel, inflorescence maturing from top	15
15	Leaves succulent with narrow pinnae, hairs microscopic, without tubers	carnosum ssp ferulaceum
	Leaves herbaceous, broadly lobed and with visible indumentum, roots tuberous	carnosum ssp carnosum
16	Inflorescence stalks densely branched, red when fresh, drying into a thorny structure persisting for one or more seasons	17
	Inflorescence stalks not drying into a thorny structure but disintegrating after flowering, with mostly only the central inflorescence rachis remaining on the plant for one or more seasons	18
17	Posterior petals auriculate	crithmifolium
	Posterior petals not auriculate	anauris
18	Inflorescence densely branched, panicle-like	paniculatum
	Inflorescence not panicle-like	adrianii
19	Leaves succulent, pinnae narrow and linear (2-3mm), appearing glabrous to the eye but microscopically hairy	ceratophyllum
	Leaves not linearly pinnate, visibly hairy	20
20	Leaves broadly lobed, laminas >3cm broad in adult plants	carnosum ssp carnosum
	Leaves pinnate to bipinnatifid, laminas <3cm broad in adult plants, usually <1.5cm	21
21	Petioles microscopically pubescent, appearing white, plants tuberous, dry peduncles and petioles persistent for several seasons	dasyphyllum
	Petioles visibly hairy, plants normally not tuberous (Klein Karoo and Koue Bokkeveld populations known with tubers), dry peduncles and petioles not persistent for several seasons	22
22	Lamina more or less as long as petiole or shorter. Pseudo-umbels per inflorescence 1-2	alternans ssp parviinflorescens
	Pseudo-umbels of 1-3 flowers. Nectar tube 3-9mm, petals auricled. Posterior petals recurved close to the tip	23
23	Lamina conspicuously longer than petiole. Pseudo-umbels per inflorescence at least 3	alternans ssp alternans
	Pseudo-umbels of 1-3 flowers. Nectar tube usually conspicuously longer than 10mm, petals not auricled	alternans ssp longicalcar

By Matija Strlic, Ljubljana, Slovenia.

Acknowledgement

With thanks to Emily Hazell, Royal Botanic Gardens, Kew, for careful reading and comments.

Subsequent changes

29/12/2022: “P. brevipetalum and P. dasycaulon, while possibly good taxa, are treated as insufficiently known for the time being. P. brevipetalum should differ from P. carnosum ssp. ferulaceum by a larger number of flowers per pseudo-umbel” changed to “P. brevipetalum and P. dasycaulon, while possibly good taxa, are treated as insufficiently known for the time being. P. brevipetalum should differ from P. parviflorum ssp. parviflorum by a larger number of flowers per pseudo-umbel.”

29/12/2023: (i) P. brevipetalum added to the key, following recent findings. The text added on 29/12/2022 removed; (ii) Koue Bokkeveld populations of tuberous P. alternans additionally referred to, following recent findings; The status of P. dasycaule clarified as insufficiently known, following recent findings.

Citation and Copyright

© The Author. This work is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License.

ISSN 2464-014X.

Cite as: M. Strlic: Draft Key to Section Otidia, Pelargonium Notes, #13 (2020).