On the verge of giving up with Masdevallia and Pleurothallis
 

Hi guys,

So I have a Masdevallia Paivaeana and Pleurothallis Rowellii. When I first got them they were in tiny plastic pots
With bark and came from a specialist nursery. To start with I kept them in the plastic pots but then the PR started developing black leaves and the nursery told me it was likely heat stress and suggested moving them to a cooler space, putting them in terracotta and spraying the top of the roots each day. I did all this but the PR lost all except 1 leaf. Now the MP is losing seemingly healthy leaves left right and centre and I'm at a total loss. I'm in the UK, they are on an East facing windowsill in a ventilated Ikea Akerbar greenhouse as the humidity in my house is quite low. Typically the temperature inside the Akerbar gets to around 20°c and the humidity sits at around 60-65%. Can you guys help me save my babies please?!

The Masdies are similar to Draculas. Most people grow these in a humid environment (greenhouse, aquarium, converted refrigerator), under lights and with a fan. I know someone that grew Masdies in a basement, lights, fans, humidity, consistent temperatures...he had quite a collection. He still has some but, lately, he has been growing Cattleyas (much easier).
Here is some information about your orchids that I hope will help you. Good luck!

https://www.orchidspecies.com/maspaiveana.htm
Masdevallia Culture Sheet - American Orchid Society

IOSPE PHOTOS

Andy's Orchids'

I am not an expert but have kept many Pleurothallis alive and flowering for a decade or so despite being a former serial orchid-killer. Mine are in self-watering pots with a combination of small bark and moss and not in an excessively warm or humid environment. Recently I over-watered and over-warmed and lost several of my long time plants. Wicking water whilst not drowning or drying out the roots has worked best for my plants. Also my temps range from 10 or lower to 20 with a draft from the window next to the plant stand. Hope you can save your RP. He's lovely.

Serial orchid killer did make ne chuckle

This might be helpful for you (scroll to the bottom). If you're willing to water a bit more frequently, and setup a humidity drip tray, then this is a good way to go.
Isle of Portland Orchids - Growing cool orchids from South and Central Americas

Personally I've had some success with masdevallias in clay pots and a mix of sphag and leca, as well as open bark mix in plastic pots. During summer I have them hanging outside under a tree, then autumn I bring them into an unheated utility room under a grow light.

Also they're very sensitive to hard water. I use rain water and not much fertiliser. Too many minerals can also make the leaves go black.

Hope that helps!

The point about using little fertilizer is a good one.

There are a couple of facts that support that:

One is the fact that it only takes about 5 grams of NPK for a plant to add one pound of mass. These tiny creatures are unlikely to add a pound of mass in the grower’s lifetime.

The second is that many of these plants get little rain, but are often shrouded and dripping from dew. Water condensed from the air contains extremely low dissolved solids - it is nature’s distilled water, after all - so the nutrient supply from host plants, microbes, etc., is meager. Plus, their root systems are proportional to the plant size, so don’t have much gathering power.

I just grow my masdies and pleuros in an unheated spare bedroom, not enclosed just sitting on a table in a west facing window. In the winter probably about 14-16C and summer 18-20C - I think the lack of air movement will be encouraging rot.

I don't spray them, just water once or twice a week - I use the water retentive orchid compost that you can buy in most supermarkets- small bark and clay substrate.

Funny you added this link as this is the nursery they came from!

Thank you all for your advice. I had her out of her pot tonight and found I may have been being over generous with the water. So she is now in fresh bark (not watered!) and I'm praying I did it in time....watch this space!