Promenzella ‘Sunlight’ is a primary hybrid between Promenaea xanthina and Warczewiczella marginata. There is some doubt as to its exact parentage since, according to some sources, ‘Sunlight’ is a hybrid between P. ‘Limelight’ and P. xanthina. I haven’t been able to get to the bottom of the mystery yet, which I find infuriating. However, it is safe to say that if the name Promenzella is correct, then the Warcsewiczella parent has brought absolutely nothing at all to the table, because the hybrid looks exactly like Promenaea xanthina, both in and out of bloom. I might charitably guess that the plant has extra hybrid vigour, but I doubt that this is the case somehow.
I was given this plant, some time ago, in an order of other orchids as a refund for the extra postage I’d paid. Only in a 6cm pot and in full bloom, it really is a miniature and should fit comfortably into anyone’s collection. There seems to be some dispute over the temperature that Promenaea should be grown at, but all I really take from this is that they are quite adaptable provided certain conditions are met, and these conditions seem to apply to quite a few members of Zygopetalinae. The first is that they do not like to dry out, and benefit from being grown in a more water-retentive medium than comes naturally to me (sphagnum moss works well, although it needs changing regularly as the plants also dislike stale conditions at the roots). With Promenaea and, seemingly, its hybrids too, it is quite easy to tell when they are short on water because the foliage turns a greyish colour, much as in the common spider plant (Chlorophytum comosum). Many of them don’t seem to like being disturbed, although this might be more the result of repotting at the wrong time (I like to wait until new shoots have started rooting, and I’ve not had any problems yet). Similar to the more commonly grown Zygopetalum, Promenaea (and Warczewiczella for that matter) are very prone to their leaves becoming marked, so it is best to keep the foliage dry if you possibly can. A lot of this comes down to the temperature and air movement though, as I grow warm with a fan blowing during the day, I find that marked foliage tends not to be a problem. Promenaea likes to grow less bright than many orchids, and leaves will scorch if light is too bright. Aim for light levels suitable for Phalaenopsis or maybe a little brighter. I should add a tip here, which is, that if you are fortunate enough to grow under lights (as I do), you can get away with growing the plants under much brighter light with no ill effects.
The flowers are the most fantastic buttercup yellow and are produced singly or in twos on short, pendulous inflorescences which hang below the foliage, usually over the edge of the pot. Inflorescences are produced from the new growth, usually two per pseudobulb, as it matures, so flowers are naturally produced at the edges of the plant rather than in the middle, allowing them to be seen without the foliage getting in the way (or, from a biological point of view, improving access to pollinators). I was concerned that the buds were blasting, as a brown spot started to appear on their reverse. However, it turns out that the throat of the flower is brown and this is what can be seen at the back of buds before they open. The colour is disappointing for the first couple of days, but the yellow intensifies as the flower ages, and they positively glow after about a week.