How to Grow it: Primula 'Arduaine'
First published in the Alpine Garden Society journal (June 2014 - Volume 82 No2 - Page 154)
Ever since I first obtained a plant of Primula aureata I've had a long and lasting passion for primulas belonging to the section petiolaris. Having fallen for the yellow flowers and heavy farina of P. aureata and its derivatives, I then discovered their blue flowered relatives and photographs of these were even more beguiling. Their location in the wild (Nepal, Bhutan & China), simply add to the appeal. Primula bhutanica is, for me, the most desirable of this small and closely related grouping but my first plant proved very difficult to keep and was quickly lost. Opportunities to obtain plants from this alliance are always brief and unpredictable so when I spotted P. 'Arduaine' on a nurseryman's stall at one of the early AGS shows some years ago I snapped it up. The literature told me this was a chance find in a Scottish garden and is believed to be a cross between P. bhutanica and P. whitei. The fact that this plant is a hybrid coupled with the fact that it was a 'garden plant' (albeit in a Scottish Garden somewhat different from my own) suggested that it might be a little easier to grow than the parent P. bhutanica. That has proved to be the case since not only have I been able to keep the plant for many years but I manage to propagate it regularly and bulk up my stock.
I believe the key to growing P. 'Arduaine' (and indeed the other petiolarid primulas) is to use a very light and airy compost. Articles in past issues of the 'Bulletin' (particularly those written by John Dennis – a very well-known and successful grower of Asiatic primulas and the petiolarids in particular) make reference to this requirement. My own preference is for a mix of equal parts leafmould; Perlite; Vermiculite and a proprietary ericaceous compost. Under no account must plants be 'firmed in' when potted up. Leave the compost 'light and fluffy'. Note the complete absence of grit or loam based compost (the staple ingredients of my P. allionii mix). In fact the regime could not be more different from my P. allionii regime since those plants are given a very firm packing whenever repotted. I have never felt inclined to try growing 'Arduaine' in the garden since I would not expect my heavy clay to be even remotely to its liking. However, given its origins, this would be worth trying by those who are blessed with conditions more akin to the 'light and fluffy'.
P. 'Arduaine' has proved easy to propagate by pulling apart an established plant to provide single rosettes which are then used to make either rooted divisions or trimmed with a short stem to make cuttings. Kept under a simple propagator lid these will soon establish and grow on. In spite of the literature stating that 'Arduaine' does not set seed, I have propagated from seed on several occasions; although, to date, none of the seedlings has proved as easy to manage as the parent. On all occasions, seed has been set following my intervention with a small steel needle charged with pollen from another petiolarid species (usually, but not always, the parent species P. bhutanica). Plants have never set seed without my help. Of course I cannot guarantee that seeds are not the result of self-pollination, although the fact that other commentators say that 'Arduaine' never sets seed would strongly suggest this clone is incapable of setting seed using its own pollen. I understand that self- pollination can be inadvertently induced by the act of introducing alien pollen to the stigma and so perhaps this possibility cannot be entirely discounted.
In my experience 'Arduaine' will happily increase and relatively quickly produce a multi-rosetted crown, but is difficult to grow into a big plant since the central rootstock rots away after a few years (usually leaving the outer ring of rosettes to continue – or in my case to serve as the next generation of divisions/cuttings).
I find that 'Arduaine' suffers little from pests/diseases although my stock is watered with Provado (Thiacloprid) a couple of times a year and the cuttings/divisions are sprayed with a proprietary fungicide. These precautions may well explain my trouble free experience.