Polystachya longiscapa

It's been a while since I have posted here, but I had a bit of time to take photos of my Polystachya longiscapa.  I purchased this plant from Afri Orchids in Summer 2019, and this is the second bloom under my care.  The type specimen was collected from the slopes of Lupanga Peak (Lukwangule Platerau), the southern part of the Uluguru Mountains, in Tanzania. The species are found in both northern and western slopes of the Uluguru Mountains at altitude 700-1680m as a lithophyte (Mytnik-Eismont et al. 2011).  In nature, this species is found in only this area, so it is a narrow endemic species.  Interesting, the Uluguru mountains appear to contain many plant species endemic to the area (Temu et al. 2008). 

 

When I saw the flowers, I thought they look quite different from the typical flowers of Polystachya. Indeed, the placement of this rather taxonomically unique species has been difficult.  Some authors separated the early branching Polystachya species into several genera; Dendrobianthe, Neobenthamia. Indeed, P. longiscapa is one of them, and it was put in Dendrobianthe (Cribb and King 2006), or monotypic genus Neoburttia (Mytnik-Ejsmont et al., 2011).  However, phylogenetic reconstruction with plastid DNA showed that P. longiscapa is sister to majority of Polystachya spp., and it diverged long time ago from the rest of the group (Russell et al. 2010).  By looking at the phylogeny, I think it is more natural to leave it and all other early branching Polystachya species in the genus Polystachya, instead of establishing several genera with a few specie in them.

When the plant is extending the long inflorescence (about 80cm long), it starts to drop leaves.  You can see in the photo below, only two leaves are left, and they are becoming brown.  The new pseudo-bulb is getting formed at the same time.  The pseudo-bulb is about 20 cm, and the leaves are about 40cm.  It is a bit too big for my grow tent, and the tip of the inflorescence was touching the ceiling of the grow tent. I grow it potted in medium bark at the lower end of intermediate temperature; the max/min daily temperature is 29/18C (84/65F) in the summer and 21/13C (70/55F) in the winter. I don't give any rest periods when they are dropping leaves.

The flowers seem to open gradually, and some older flowers drop before all flowers open.  They may make a bigger display if they open at the same time, but I can enjoy the flowers longer. The flowers are slightly fragrant.

 

Literature cited:

Cribb, P., & King, K. (2006). 556. Polystachya longiscapa: Orchidaceae. Curtis's Botanical Magazine, 23(2), 153-156.

Mytnik-Ejsmont, J., SZLACHETKO, D. L., & Baranow, P. (2011). Neoburttia, a new genus for Polystachya longiscapa (Polystachyinae, Orchidaceae). Pol. Bot. J, 56(1), 45-49. (link to PDF)

Russell, A., Samuel, R., Rupp, B., Barfuss, M. H., Šafran, M., Besendorfer, V., & Chase, M. W. (2010). Phylogenetics and cytology of a pantropical orchid genus Polystachya (Polystachyinae, Vandeae, Orchidaceae): Evidence from plastid DNA sequence data. Taxon, 59(2), 389-404.

Temu, R. P. C., & Andrew, S. M. (2008). Endemism of plants in the Uluguru Mountains, Morogoro, Tanzania. Forest Ecology and Management, 255(7), 2858-2869.