Spring is here, almost (Primula denticulata)

This blog post was originally written over 3 years ago! Though it is now late in 2020, and the pandemic is still with us, looking ahead we can hope that life returns to normal soon. Primula denticulata is surely a wonderful symbol of that hope.

One of the most photographed Primula in the wild is the showy and locally abundant species, Primula denticulata. It is distributed across the Himalaya from Afghanistan through to Sichuan, but it was first collected in Nepal. It was described in 1805 by James Edward Smith and the original description includes a painting. The type specimen LINN-HS 271.2.2  (Herb Smith) was collected by Dr. Buchanan and resides at the Linnean Society. The type location is "the moist parts of the hills about Chitlong in Nepal, flowering from February to April". Buchanan's journey is detailed in "An Account of the Kingdom of Nepal", written in 1819. Chitlong (27°38'59.27"N 85°10'12.17"E) is very near to Kathmandu, though overlooked by plant enthusiasts as they head for more popular trekking areas.

Primula denticulata color forms

 

 This species varies across its distribution and authorities have disagreed on the distinctions, creating numerous species which have since been lumped into P. denticulata including P. adenophora, P. aequalis, P. alta, P. cyanocephala, P. harsukhii, P. hoffmeisteri, P. limnoica, P. paucifolia, P. platycrana, P. sinodenticulata, and P. telemachica. A one time even P. capitata and P. erosa were thought to be synonymous. Primula cachemiriana, described from cultivated plants, persists as a name given to plants covered with dense yellow farina. Adding to the confusion are dwarf states which resemble P. atrodentata but can be distinguished by the presence of persistent basal bud scales which were once part of the winter resting bud. 

P. denticulata basal scales flatten to reveal true leaves and flower buds

  Many garden selections have been made. The compact flower heads are composed of numerous erect flowers in shades of purple, pinkish-purple, reddish-purple or white. It is winter hardy in my garden in Calgary, Canada though it does resent water around the resting bud in winter. It is easily grown from seed, which is produced in copious amounts and can be vegetatively propagated by splitting crowns or by root cuttings.


Masses of plants in Bhutan

 

Pam Eveleigh © 2020

 

 

 

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Primula sinensis....or Not

Primula sinensis is a familiar houseplant, though perhaps not as popular as it has once was. Like Primula obconica, this species is known for its beautiful variations in flower colour and form . Because of this variability and its availability at the time, it was the subject of some of the first studies done on genetics and heredity. Using the principles of Gregor Mendel ,  R.P. Gregory conducted experiments with Primula sinensis from 1903 until his death in 1918, investigating 18 pairs of characteristics as described in a posthumous paper by co-collaborator William Bateson (see also Mendel's Principles of Heredity, A practical Example starting pg 293, with color illustrations). With all its variations, it is no wonder it was a popular garden plant, still desired, but unfortunately it can cause allergic contact dermatitis which may have contributed to its scarcity today.

Primula praenitens from Bot. Reg. 7:t 539. 1821.

The origins of Primula sinensis in the wild are unknown as the original material came from gardens at Canton (Guangzhou), China. It was described with illustrations twice in 1821, as Primula sinensis Sabine ex Lindley in Coll. Bot. (Lindley) t. 7. 1821 and as Primula praenitens Ker Gawler in Bot. Reg. 7: t. 539. 1821. The description by Ker Gawler points out the previous use of the name Primula sinensis by Loureiro in 1790 which is given as the reason for using a different name than that given by Sabine. Though this is indeed the case, it was thought that Loureiro's name was invalid and so the name Primula sinensis has been used since. However, it is now determined that Loureiro's description is valid and so Primula sinensis Sabine ex Lindley is now "nom. illeg." The name Primulidium sinense (Sabine ex Lindley) Spach was also published in Hist. Nat. Veg. (Spach) 9:355. 1840 but this is deemed nom. illeg. as being superfluous for Primula praenitens.

So the correct name for this species is Primula praenitens!

According to John Richards, the name "Primula sinensis" is "conserved", but I can find nothing official in the International Code of Nomenclature list of Conserved & Rejected Names though the most recent version is not yet available online. Richards also notes that Primuls sinensis may be only the cultivated form of the wild species, Primula rupestris which was described in 1918 by Balf.f. & Farrer.
Halda considers Primula rupestris to be a synonym of Primula sinensis and discusses this in his book "The Genus Primuls in Cultivation and the Wild", pg 63.
The Flora of China published the name Primuls sinensis but the online version notes that the correct name should be P. praenitens. It lists Primula sinensis as being from Guizhou and Sichuan and Primula rupestris from W Hubei and S Shaanxi and the two are distinguished in the key by Primula sinensis having a larger calyx in fruit and not retaining old leaves around the base of the plant (and by location).

Historical images taken by Ernest Henry Wilson are here and here. A beautiful image from the wild can be seen here.

So what is the species described by Loureiro as Primula sinensis? I guess that will be the subject of another post!

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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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