Once or twice per year, the US Botanic Gardens offers the opportunity to tour their production greenhouses which are on a separate location from the public greenhouses. This is where they maintain collections and produce things like the bedding plants you see around the facility. They have a wonderful collections of orchids, succulents, and more.
They have a great variety, but also may have multiples of the same thing - usually because they've had it long enough to divide it many times. But sometimes, they keep the plant together and just pot it into a giant milk crate, like this Isochilus major. The plastic basket it is in I'll estimate to be approximately 30 by 18 inches, maybe a bit bigger, with the plant spilling out of it in every direction.
There was a nice assortment of Epidendrums, but due to their octopus like nature I had a hard time identifying source pots and therefore names. So these are just interesting pictures.
There was also quite a crop of dendrobiums, especially a large number of classic Nobile hybrids. They were all above my head so I can't give you a name on them, but they all looked rather like the old style hybrid that is slightly larger and needs colder temperatures in the winter to set buds. Still very nice of course.
Among the dendrobiums of note were Dend. caryicola on the left, which was labeled as a CITES seizure. If you fancy it there are a number of quite similar species available, such as Dendrobium aphyllum. I'm not sure I can tell the difference between them. The photo on the right shows Dend. speciosum. This is the first time I've seen one of those in person and the plant is massive. The canes were about 2 inches in diameter and about 2 feet long topped with a pair of thick, one foot long leaves, generally looking like a large Cattleya type thing. The plant was not very attractive, but the flowers are quite nice.
Of the many lovely paphs and phrags in bloom, there was one Paph. De Witt Smith which I was quite smitten with. I'd like to get some seedlings of this, but I suspect I'll not be able to find any. The plant is large so they've had it a while, and one sad thing about paph hybrids is that often you only see them for a short period of time and then you don't get an opportunity to buy that one ever again. With few exceptions they just don't get remade. Fortunately there are plenty of other exciting things to be growing.
These two closely related species are Paph. glaucophyllum and Paph. victoria-regina. These and related species and hybrids are great things to grow because they produce multiple flowers sequentially over a period of months.
A very adorable Pleuro. circumplexa. This is a small species about 5 inches tall.
Gongora scaphephorus, like all Gongoras, was well flowered on an elegant, pendant spike. These flowers were also nicely fragrant, but I can't remember what it smelled like. Citrus-ish, perhaps?
I will leave you with a couple photos from the succulent house. Above is Pachypodium succulentum, an interesting caudiciform species. I've never grown this one but have been pleased with the other Pachypodium species I have tried. They seem hardier than the more commonly seen Adeniums in my opinion.
A violently red-orange Echinocereus triolochidatus in full bloom.
They have many other plants in other greenhouses - gingers, anthuriums, bedding plants, cycads and more. Visiting the main public complex located next to the capitol building in DC will give you quite a display and impression of the variety of their collection. I highly recommend it!