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. 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. A discussion on the status of P. dasycaulon is 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 10
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 a thick main root, without side tubers parviflorum ssp parviflorum
Plants with side tubers parviflorum ssp tuberculum
10 Leaves simple to shalowly lobed, base cuneate, margin undulate to crenate klinghardtense
Leaves different, mostly pinnate or lobed to rachis 11
11 Inflorescence multi-flowered, taller than 10cm 12
Inflorescence few-flowered, up to 10 flowers (can be more in cultivation), not taller than 10cm 18
12 Pedicel shorter than nectar tube 13
Pedicel longer than nectar tube 15
13 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 14
14 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
15 Inflorescence stalks densely branched, red when fresh, drying into a thorny structure persisting for one or more seasons 16
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 17
16 Posterior petals auriculate crithmifolium
Posterior petals not auriculate anauris
17 Inflorescence densely branched, panicle-like paniculatum
Inflorescence not panicle-like adrianii
18 Leaves succulent, pinnae narrow and linear (2-3mm), appearing glabrous to the eye but microscopically hairy ceratophyllum
Leaves not linearly pinnate, visibly hairy 19
19 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 20
20 Petioles microscopically pubescent, appearing white, plants tuberous, dry peduncles and petioles persistent for several seasons dasyphyllum
Petioles visibly hairy, plants normally not tuberous (only one Klein Karoo population known with tubers), dry peduncles and petioles not persistent for several seasons 21
21 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 22
22 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.


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

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).

Leave a Reply

Your email address will not be published. Required fields are marked *

This site uses Akismet to reduce spam. Learn how your comment data is processed.