STEPHEN G. HAW

Paeonia delavayi, a variable species

The New Plantsman 8 (4) dec. 2001 251-253

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In a recent article in The New Plantsman (Haw (2001)), I accepted the conclusions of D. Y. Hong, Pan and Yu (1998), that ihe Paeonia delavayi complex (i.e. Paeonia L. subgenus Moutan (DC.) Seringe Section Delavayanae (F C. Stern) J. J. Halda) could be divided into only two species. P. delavayi Franch. and P. ludlowii (Stern & Taylor) D. Y. Hong. This makes good taxonomic sense, but clearly causes some problems for gardeners, as plants that are quite distinct for horticultural purposes are now all merged into the single species, P. delavayi. A glance at the synonymy of this species given in my article (Haw (2001): 167) will make the problems obvious. I now propose to resolve at least most of these problems by dividing this one species into two varieties and several formas. It must he borne in mind, however, that intermediates between these varieties and formas certainly exist in the wild, so that distinctions between them are not by any means entirely clear-cut.

Some populations of P. delavayi tend to be much lower-growing than others. This difference often persists in cultivation and is not merely a result of growing conditions. Even D. Y. Hong, Pan and Yu (1998: 555) note that one of the populations they studied included only short plants rarely reaching 1 m in height, with only current-season shoots above ground and woody parts underground. These low-growing, often subshrubby plants differ markedly from taller plants reaching up to about 1.8 m in height. Intermediates certainly exist, but it seems reasonable to recognise two varieties of this species on the basis of height.

Within these two varieties there is a wide range of flower colour. In both varieties, plants with flowers of various colours exist. I propose to recognise major colour variants as formas within each of the two varieties. Intermediates undoubtedly occur, sometimes possibly as the result of hybridisation between different colour forms, but most plants can be assigned with little difficulty to one or other of the formas. Hybrids are known to occur in the wild: see photograph of a hybrid swarm photographed in the Zhongdian region, NW Yunnan in The New Plantsman 8: 169 (2001).

TAXONOMIC TREATMENT

Paeonia delavayi Franch., Bull. Bot. Soc. Fr. 33: 382 (1886); Huth, Bot. Jahrb. 14:273 (1892); Stern, Stud. Gen. Paeonia 44 (1946); K. Y. Pan, Fl. Reip. Pop. Sin. 27: 47 - 48, pl. 5 (1979); D. Y. Hong, K. Y. Pan & H. Yu, Apn. Missouri Bot. Gard 85: 554 - 564 (1998). Typus: China, NW Yunnan, Likiang [Lijiang], Delavay 1142 (holotype P - n.v., isotype K).

For a description of this species, see Haw (2001: 167).

KEY TO VARIETIES

1. var. delavayi

KEY TO FORMAS

1a. var. delavayi f. delavayi

Syn. P. delavayi var. atropurpurea Schipcz., Not. Syst. Herb. Hort. Petrop. 2: 47 (1921)

Included in this forma are all taller-growing variants of the species with predominantly red flowers in this type forma: P. delavayi of gardens, with dark red'flowers belongs here.

1b. var. delavayi f. lutea (Delavay ex. Franch.) S. G. Haw, stat. nov. Typus: China, NW Yunnan, Eryuan County, Mt Hea Chan Men, 25 May 1883, Delavay s.n. (lectotype, P - n.v., isolectotype, K);

Syn. P. lutea Delavay ex Franch., Bull. Soc. Bot. Fr. 33: 382 (1886); Huth, Bot. Jahrb. 14: 272 (1892); P. delavayi var. lutea (Delavay ex Franch.) Finet & Gagnep., Bull. Soc. Bot. Fr. 51: 524 (1904); P. delavayi var. lutea f. superba Lemoine, Rev. Hort. 14 (1906); P. lutea var. superba (Lemoine) hort. ex Gard. Chron., Ser. 3, 44: 50 (1908); P. x handel-mazzettii J. J. Halda, Acta Mus. Richnov., Sect. Nat. 4 (2): 31 (1997).

Included here are all the taller-growing variants of the species with predominantly yellow or orange flowers. Orange-flowered plants may be the result of hybridisation between plants with yellow and red flowers and their inclusion here is therefore more or less arbitrary. P. delavayi var. lutea of gardens belongs here.

As far as I can ascertain, there is no clear record of white-flowered plants tall enough to be placed with this variety.

2. var. angustiloba Rehder & Wilson in Sarg., Pl. Wilson. 1: 318 (1913). Typus: China, W Sichuan, W of Tachien-lu [Kangding], descent to Yalung River [nr. Yajiang], 3000 - 3600 m, Oct. 1908, Wilson 1333 (holotype A - n.v.). Syn. P. potaninii Komarov, Not. Syst. Herb. Hort. Petrop. 2: 7 (1921).

Here belong all the low-growing plants* of this species, attaining not more than 1 m in height. Previously they have often been regarded as a separate species, (e.g. by Stern (1946: 49-50)). The flower colour varies from dark purplish-red through yellow to white and I accordingly recognise three formas on the basis of this colour variation. The name var. angustiloba has priority in this rank, having first been published in 1913.

* [Ed. In the wild the normal tall clump-forming plants of P. delavayi var. delavayi are in marked contrast to the low-growing var. angustiloba. Whereas the former produces tight clumps and only occasionally suckers, the latter is often widely suckering and, on occasions, no more than 30 cm tall in flower.]

KEY TO FORMAS

2a. var. angustiloba f. angustiloba

This name includes the typical 'P. potaninii', a low-growing plant with deep maroon-red flowers.

2b. var. angustiloba f. trollioides (Stapf ex Stern) S. G. Haw, stat. nov. Typus: China, NW Yunnan, Deqen, Baima (= Beima) Shan, Mekong-Yangtse divide, 11,000 ft., open stony pastures, Forrest 13195 (holotype, E).

Syn. P. trollioides Stapf ex Stern, Journ. Roy. Hort. Soc. 56: 77 (1931); P. potaninii var. trollioides (Stapf ex Stern) Stern, Stud. Gen. Paeonia 50 (1946); P. X franchetii J. J. Halda, Acta Mus. Richnov., Sect. Nat. 4 (2): 31 (1997).

I include plants with orange flowers under this name, but, as noted under var. delavayi f. lutea (above), these may be the result of hybridisation between plants with red and yellow flowers, so this inclusion is more or less arbitrary.

2c. var. angustiloba f. alba (Bean) S. G. Haw, stat. nov. Typus: t. 49 in Stern, Stud. Gen.

Paeonia (1946) (holotype).

Syn. P. delavayi var. alba Bean, Trees and Shrubs 3:265 (1933); P. potaninii f. alba (Bean) Stern, Stud. Gen. Paeonia 49 (1946).

This name is applied to white-flowered, low-growing plants of the species, which Sir Frederick Stern (1946: 49) called P. potaninii f. alba.

This classification separates all the most commonly cultivated variants of this species at least at the rank of forma. If it is found necessary to distinguish between cultivated plants that are assignable to the same forma, then it will probably be appropriate to use cultivar names. P. delavayi is a suckering plant that is often propagated vegetatively, so that distinct clones can readily be maintained in cultivation.

BIBLIOGRAPHY

Haw, S. G. (2001). Tree Peonies: a review of their history and taxonomy. The New Plantsman 8 (3): 156-171.

Hong, D. Y., Pan, K. Y. & Yu, H. (1998). Taxonomy of the Paeonia delavayi complex (Paeoniaceae). Annals of the Missouri Botanical Garden 85 (4): 554 - 564.

Stern, F. C. (1946). A Study of the Genus Paeonia: London, RHS.

Stephen Haw, Worton Edge, Over Worton, Chipping Norton, Oxfordshire, 0X7 7EW