Oca and the wonderful Album Vilmorin

I had not expected to write anything new today, as we are far away from the garden, wandering around the streets of Antwerp. However, I am drawn like a magnet to book shops – even if the books on display are in languages I do not read, as attested by the recent purchase of two books from a garden centre in Finland. Browsing through the second bookshop I stumbled upon today, I came across a wonderful book: a collection of prints of the 46 colour plates that together form the Album Vilmorin – Les Plantes Potagères, along with interesting historical notes and information on the plants, in English. I had seen these before, but not in such a volume. Vilmorin, a renowned French seed company issued one plate per year, in the years 1850 to 1895, each comprising beautiful botanical illustrations of a collection of fruits and vegetables from their catalogue.

Album Vilmorin 1869

There was never any doubt that this book was leaving the shop with me, but as I flicked through, something in particular caught my eye – plate Nº 20, 1869 – at the bottom of which are two illustrations of oca (Oxalis crenata, syn. O. tuberosa) – both a yellow form and a red. Plants of genus Oxalis are referred to as wood sorrels, which might readily cause some confusion with the perennial herb, common sorrel, that is more familiar, either as an addition to salads or as used in soup. Common sorrel is from a different family, although shares with wood sorrels a bitter taste derived from oxalic acid, which is toxic in sufficient quantity. Oca, or oka, is a small, often colourful, somewhat potato like, tuber native to the Andes. I became aware of this interesting vegetable only a couple of years ago, and have yet to grow it, although it is ‘on my list’. I was interested to see it in such an old publication, as I had garnered the entirely false impression that its presence in Europe was more recent. I should have known better.

I have since found reference to oca in the Arcana of Science and Art from 1835, which suggested that it “…has been much talked of, as an auxiliary to the potato…”. The previous year’s edition gave only brief mention of its introduction, supplying a date of 1831 for the first planting of the tuber in this country by a Mr Lambert, from a tuber brought from South America by a Mr David Douglas. John Rogers, in The Vegetable Cultivator, 1839, describes the crop in some detail, including successful methods of its cultivation, and noting that “…in the course of three or four years it was found to be quite as hardy as the potato…”. Rogers also described the means of its introduction to this country, which agrees with that previously noted, but supplies a date of 1832. Rogers notes the use of not only the tuber, but also the succulent stalks for tarts, as a substitute for rhubarb, as well as a fodder crop. John Claudius Loudon, in The Horticulturist, 1849, also concurs on a date of 1932. However, he goes on to note that “the plant was much cultivated ten years ago, but is now out of repute”, with another species of the Oxalis genus coming into favour, O. deppei (syn. O. tetraphylla), and said to be of superior flavour. He notes, however, the continued use of the stalks and leaves in tarts. O. deppei did not seem to fare much better, there being little reference to its cultivation as a food crop here, although it is mentioned for various decorative uses.

A great many publications of the 1830s refer to the cultivation of oca, some in quite positive terms as an “improvement on the potato”. One interesting point that is noted in several such publications is that it is best planted not whole, as one would with a potato, but by cutting sections with one or two eyes – as with potatoes, these are the points on the tuber at which new vegetative growth will spring forth. With oca, the eyes are typically colourfully marked on the skin so readily identified. Oca was observed to have a tendency to produce much vegetation at the expense of developing useful sized tubers. Planting sections with few eyes was one suggested way of combating this excess growth, as was the cutting down or thinning out of the foliage. This is certainly advice to consider when I eventually get around to trialling this crop myself. Also advised is the exposing of the harvested tubers to sunlight, which is practiced in its native environment and has the effect of reducing the levels of oxalic acid. Again, a divergence from the cultivation of potatoes, as one would not expose those to sunlight for very long, as they turn green and inedible. When harvesting main crop potatoes for storage, it is good practice to spread them out in the sunlight for just a couple of hours to help set the skins, before moving into the dark from which they should not be exposed further. Another difference is that oca can be eaten raw, in addition to preparations along similar lines to potatoes.

That it fell out of favour is clear from its decline into relative obscurity, until revived at least a little by recent renewed interest in exotic crops. The initial excitement surrounding this vegetable, and even some degree of success in its cultivation, failed to secure it a regular place in the kitchen garden. The potato remained untoppled by this much more modern import. It has, however, one particularly significant advantage over the potato; namely, the latter’s susceptibility to blight – more specifically, late blight, Phytophthora infestans – that caused so much devastation from the mid 1840s. Late blight was as yet unknown when oca was first introduced here. John Lindley, author of a text that I have found to be most useful in selecting interesting varieties of top fruit, A Guide to the Orchard and Kitchen Garden, 1831, writes in a later publication, A Natural System of Botany, 1836, that “…the tubers are insipid, and not worth cultivation; for which, however, they have been recommended of late years…”. He does, however, give some small reprieve in that “…the stalks of this species are intensely acid, and make an excellent preserve.”. By the turn of the century, it had all but disappeared from note. It is included, if somewhat briefly, in The Book of Rarer Vegetables, by George Wythes and Harry Roberts, in 1906. Here its introduction is dated to 1829, but from the more detailed accounts of its introduction in the preceding literature, a date of approximately 1832 seems most likely.

This all goes to remind one of the range of fruits and vegetables that were cultivated in years past. Some vegetables that have only relatively recently become popular once again, as our tastes have broadened alongside low cost travel and transportation, were once commonly cultivated in the great gardens of the 1800s. Still others have yet to experience any sort of revival, and are now rarely cultivated. The Victorians were enthusiastic plant collectors, bringing seeds and plants of both decorative and edible sorts back from their extensive travels, and then somewhat unreasonably expecting their head gardeners to be able to cultivate these plants hailing often from rather different climes. The head gardeners of the time were, however, extraordinarily adaptable and often found a way to cultivate plants that were rather marginal propositions. Something of that enthusiasm seems to have been lost as these gardens fell into decline in the 20th century. I find perusing horticultural texts from the period, which tend to be written with practical cultivation in mind, fascinating indeed. The scholarship of the authors, the range of cultivars described, especially of top fruit, and the scale of the texts, are simply astounding, and there remains much merit in what is written, even for gardeners of today. Indeed, there are no modern equivalents to these great works that I am aware of. Organic gardeners may be especially interested in texts written before the advent of synthetic fertilisers and pesticides, rampant use of which has blighted agriculture for so many years. Many such texts are now freely available online in digitised form.

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