We’re Orchidding Around

Longwood’s Orchids // Collection Management // Wild Orchid Conservation // Orchid Breeding // Orchids are very confusing & interesting

Sorry about the pun, it’s terrible but I couldn’t help it  😉

I’ve been working in Longwood’s Indoor Display department since I got back from Miami. I’ve worked in a few different areas but predominantly I’ve been working with the Orchid Grower, Greg, at my request. I find orchids fascinating but they are DIFFICULT and CONFUSING, and I had forgotten most of the amazing things we were taught by Kerry Waters at RBGE. So this has been a great opportunity to sort out my Paphiopedilum from my Phragmipedium, my pollinium from my pollinaria and my stipe from my viscidium.

Longwood has a large orchid collection that was started by Pierre S DuPont back in the 1920s. They still have some orchids from this time in the currently approx. 6,300 strong collection- really old orchids! There are about 2,200 different varieties, of which a large proportion is Cattleya and things that look to me like cattleyas but probably aren’t (like Laeliocattleya, Brassolaeliocattleya,  Sophrolaeliocattleya, Cattleytonia, Brassocattleya… not confusing at all, right?). The orchid collection is very significant to Longwood and the annual Orchid Extravaganza is hugely popular.

Unfortunately, much of the collection is infected with virus: either odontoglossum ring spot virus or cymbidium mosaic virus. This doesn’t necessarily kill the plants (many have been infected for decades) but those that survive are weaker, the foliage becomes ugly and the flowering can be affected. Currently, Greg- who’s been in position for 18 months- is waging an epic and brutal campaign to eradicate the virus with the following battle tactics…

  1. Replace the less important/readily available stock with clean plants from outside Longwood.
  2. Improve the health of the remaining plants with better watering, feeding & environmental conditions and repot the entire collection. This will promote growth of the orchids to the extent that they can grow faster than the virus can spread within the plant. Then you can remove the new, virus-free growth and chuck out the old & infected part of the plant.
  3. Stop any further spread of the virus. Luckily it’s spread mechanically- it’s not airborne or waterborne- so avoiding contact between plants and sterilising tools/ hands makes a huge difference. In practical terms this means you have to sterilise tools with a blow-torch and wear a different pair of rubber gloves for each individual  plant. That’s a LOT of rubber gloves. Actually now I come to think of it, I’ve spent a good deal of my time at Longwood wearing rubber gloves and sterilising things. Hmmm.

This is obviously a big task and there are some issues which make it even more difficult, like how complicated orchids are to look after and the fact that the greenhouses holding the collection are very old and not ideal for orchid growing. However, there are lots of plans for improvement so things are looking up for the collection.

Whilst working with Greg, I’ve learnt a lot about the management of tropical, subtropical & temperate orchids, as well as learning a few more genera and improving my understanding of the family. I’ve done a range of different things but the important things I’ve learnt include particular ways of watering different genera/species of orchids (they’re really fussy), how to pot them up correctly (they’re really fussy) and how light and temperature can alter flowering and growth (they’re really fussy). Of course it’s all worth it because the flowers are so beautiful, varied and unlike any other angiosperms- or “Those Soil Plants” as Greg calls them. Here are few new-to-me orchid growing tips that I’ve picked up…

  1. Tropical epiphytic orchids like to be potted tightly- some extremely tightly. For example, when potting Phalaenopsis (the orchids you buy from Tesco), you should play the game of “how small a pot can I shove this huge mass of roots into, and how much of the growing medium can I crush in there with them?” Obviously using immense skill & precision all the while. Ahem.
  2. You should always position your orchids so that the new growth is facing towards the south//the direction of most light (unless it’s a species which grows evenly in a circle in which case it doesn’t matter): this will encourage the new growth to be upright instead of reaching for the light and getting all wonky
  3. The necessity of see-through pots is a total myth. Although many epiphytic orchids have green roots, they don’t contain the correct structures for full photosynthesis and therefore the amount they contribute to the plant is negligible. Clear pots are handy for keeping an eye on the amount of root growth but are not required- so don’t feel like you have to shell out extra for them.

I’ve also had the opportunity to help out with a bit of orchid breeding: both for conservation purposes and for aesthetic purposes. More of The Science!

I left Greg and went back to the research department for a couple of days to accompany the research curator, Peter, in collecting some Cymbidium parviflorum seed pods from the wild, from the same population that we visited in flower back in May (see here if you missed it), and another population he’s been working with. Peter is initiating a native orchid conservation project at Longwood, working with landowners and land conservation organisations to collect wild seed of local species, grow them on and return them to the wild, as well as keeping some at Longwood.

Of course it was brilliant to go off hunting in the woods for orchids again, and much harder since they no longer had bright yellow flowers to make them easy to spot! It was also fascinating to learn about how to sow the seeds for successful germination because, yes you guessed it- they’re really fussy. Orchid seeds are all absolutely tiny and look like little specks of dust when they are mature. They are notoriously difficult to germinate because they require very specific conditions, such as the presence of a fungus to provide it with sugars (there is specific fungus required by each species); and the seed can have very strong dormancy. However, if you sow the seed when it is immature you can overcome these issues. Somehow, the immature seed will just grow straight into being a plant if you sow them onto sterile agar containing the correct sugars & minerals for that genus/species. Interestingly, Cypripedium germination is most successful when you put a bit of potato in with the agar solution. Weird, right? Apparently there are some kinds of plant chemicals which encourage germination and so growers have taken to putting different bits of fruit & vegetables in with the seeds, depending on what the species of orchid. No one knows why, but Cypripediums like potatos and Orphrys (that’s our UK native bee orchid) like radish. So that’s what we did! We collected the seed pods when they were mature enough to be viable, but not fully mature, about 50 days after pollination. I then sterilised the pods using bleach and sowed them in the tissue culture hood, in agar mixture T839 for Cypripediums, with a little cube of russet potato in it. And guess what- they’ve germinated! Win! I now have plans to build a clean room in my house, and am putting in orders for agar, petri dishes & radishes…

Aside from orchid cultivation for conservation, I’ve also helped out with some propagation for aesthetic purposes. Longwood is possibly alone in North America in holding a large collection of Disa uniflora, a rare orchid from South Africa which is very beautiful. Look:

IMG_0044
Gorgeous. One of Longwood’s Disa Hybrids.

Longwood has been growing & breeding this orchid since the 1960s when they collected it from the wild. It is very short-lived, often dying after flowering and so needs to be regrown from seed regularly. Longwood’s orchid growers have always bred the species by selecting for particularly good traits and have also hybridised it with other species of Disa. I was lucky enough to help Greg do some breeding with the Disa, and to work with the results of last year’s breeding: transferring seedlings from test tubes into the real world. It turns out that the hardest parts of orchid breeding are 1. having enough understanding of orchid genetics to know which plants to pollinate with which; and 2. keeping records of what you’ve done! The actual pollinating bit is easy & the sowing and pricking out isn’t so difficult either.

I’ve finished my stint working with Greg now, and am off to work in the rest of the conservatory for a bit, before going to join the outdoor department for my final rotation. It’s been a fascinating few weeks & I’ve learnt a lot- thanks Greg!

 

 

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