Understanding Primula odontocalyx

In the Spring 2015 AGS/SRGC show at Kendal, a plant was shown as “Primula aff. odontocalyx” and this has resulted in discussion over whether this is Primula odontocalyx or not.

P. aff odontocalyx: courtesy David Rankin

Primula odontocalyx was first described as a variety of P. petiolaris in 1895, but was then elevated to species status by Pax in 1905. The species was based on Farges971 collected near Tchen-kéou-tin (now Chengkou  county, NE Sichuan). The plant in question came from Wushan county, just south of Chengkou so the location is a good match. The Flora of China gives the distribution as S Gansu, W Henan, W Hubei, S Shaanxi, Sichuan, but not W Yunnan (Mekong Salween divide) where apparently the BASE 9547 P. aff. odontocalyx was collected. The similar and related species P. euosma is from that area and the BASE collection may be that species.

The description of the species says that the large flowers are borne on a scape and that the calyx has 2-3 teeth on the apex. There are 3 sheets of Farges 971 in the Paris herbarium, showing 9 plants in total. Most are 2-3 flowered, but vary from single flowered to 6 flowered.  Though a key characteristic is the calyx teeth, and the species was named for this feature, not all of the type specimens show this. Some are entire and undulating. This is a discrepancy noted previously by Smith & Fletcher. The show plant is white flowered but this was a variant in a normal purple with a white eye flowered population.

The plant in question spreads vegetatively by short stolons and this feature isn’t seen on the herbarium specimens nor is it mentioned in the description of P. odontocalyx, but the material available at the time was limited and the plant was not in cultivation then.

Links to the relevant descriptions, herbarium sheets and more images are available in the species gallery under P. odontocalyx. In general it seems as though the description of the species P. odontocalyx was unfortunately difficient causing uncertainty about this species. There is no doubt in my mind that this plant in question falls within P. odontocalyx.

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Primula marginata

One of the earliest Primula species to bloom in the spring is Primula marginata. This species was described in 1792 from garden grown plants collected from the wild in 1781. In the wild, it almost always grows on limestone, on mossy or grassy ledges on steep cliffs, boulders or slopes or from crevices, usually on the north side. Probably the most striking feature of this species is the irregular leaf edges lined with farina and the variation in this feature is what endears it to gardeners. Named and selected forms vary in the leaves and also in the bluish tone and size of the purple flowers. It is amazing that in the wild so many variants grow side-by-side.

Like other members of the Auricula Section, the plant produces elongated stems as the lower leaves die and new leaves are produced from the growth point. The plant will produce side branches along this lengthening stem and if the stem or side branches are underground or in contact with the soil, roots will be produced, making it a simple process to encourage the plants to make viable offshoots that are easily detached from the mother plant. In the garden, floppy plants with long stems are less desirable, but it is just a matter of burying the plant so that the neck is level with the soil again to tidy it up. I remove the dead leaves before doing so.

Three forms of Primula marginata in cultivation

Wild Primula marginata showing old stems

 

Remove dead leaves, plunge plant so that the growth point is just above the soil

 

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Primula boreiocalliantha

Primula boreiocalliantha is one of the most beautiful species that I have seen in the wild. In 2009, and again in 2014, I saw it near to Hong Shan in Yunnan and then again in 2014 in Muli, Sichuan. This species has  4 synonyms : P. coryana (from Muli), P. muliensis (from Muli), P. propinqua (from Yunnan) and P. hongshanensis (from Yunnan). It is distinguished by large, rose purple flowers to 3.5cm wide and spear shaped leaves, thickly coated with farina below. The flowers appear in tiers or whorls. This species seems to require specific growing conditions, usually under mature rhododendrons with little competition from other herbaceous plants. I have seen it growing in the company of P. szechuanica and P. secundiflora.

 

The video below is from Hong Shan in 2014. More images are in the Species Gallery.

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Kingdon-Ward 1914 Burma expedition

This expedition is detailed in Kingdon-Ward’s book “In Farthest Burma”, Seeley,Service & Co. Ltd. London, 1921. The principle area covered is the divide between the ‘Nmai Hka river in Burma and Salween river in Yunnan, with the most time spent exploring the area around Hpimaw. Included is an appendix with a list of many of the collections made in 1914 and also a later expedition of 1919. Very few Primula species were seen on this expedition, but they included P. fragilis, P. coryphaea (now bella) and P. sciophila (now bella) which were then described as new. Kingdon-Ward thought that he had found P. beesiana below the Feng-Shui-Ling (pass), but this was later described as a new species, P. burmanica. Other species listed by Kingdon-Ward in his book are P. praticola (now taliensis), P. seclusa (now mollis), P. calliantha, P. involucrata, P. helodoxa, P. serratifolia, P. euosma, P. sonchifolia, P. limnoica (now denticulata), P. listeri and several undetermined species. The determinations on these might have changed since the book was published.

Primula burmanica

Kingdon-Ward's route in 1914 in Upper Burma

Last year, North Face and National Geographic sponsored an expedition to Myanmar (formerly Burma) with the goal of measuring the height of the mountains Hkakabo Razi and nearby Gamlang Razi to determine which was higher. The expedition is detailed in a blog, but more significant is the fact that access to the northern part of Myanmar is now possible though still difficult. Trips from Fort Hertz (now Putao) can be arranged. The most productive area of Kingdon-Ward's route was near Hpimaw Fort 26° 0'0.64"N, 98°38'0.47"E which is just over the border into Western Yunnan, China and possibly not open to foreigners. Of particular interest would be to find Primula densa (KW 3536) which was found on the Burma side, just south of Gaulam, and within 10kms north of Hpimaw. The type specimen of this species is very meager and though there are images of plants identified as this species from Arunachal Pradesh, images from the type location would be valuable. If you are planning a botanical trip to northern Myanmar, please contact the webmaster.

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