Masdevallia striatella leaves yellowing

[ejramer]

I recently bought a Masdevallia striatella and to my dismay found that it had some patches of scale. I cleaned those off with rubbing alcohol yesterday, and today some of the leaves (the ones I cleaned and possibly a couple others) are turning yellow in blotches. Could this be from the rubbing alcohol? Or are my conditions not favorable? I have it in indirect sunlight (sheer curtain, patches of shade from other orchids) during the day, approximately 70-75* F. At night I've been moving it outside to benefit from the 50*F nights. Is the moving between indoors and out too much stress? I would leave it outside all the time but I don't have a good growing area, only a west-facing patio that gets very strong afternoon sun and none during the rest of the day. I'm in an apartment so I can't set up or plant anything outdoors except on my patio.
First photo: before cleaning scale. Second photo: after cleaning scale (5 days apart).

[Roberta]

Scale insects suck the juices from the underside of the leaf, and often the first thing one notices is the yellow spot on top of the leaf when the scale is on the bottom. So cleaning off the scale didn't cause the problem... if you had left it a bit longer, you would have seen the yellow above with the scale below. It just took a bit of time for those chlorotic areas to appear. The scale had already done its damage. All the moving might be a stressor... is there any chance that you could rig something to shade the plant outside from that western sun? Masdevallias typically like shade, don't need a lot of light. Temperatures both day and night sound pretty close to ideal. Where to you live?

I can't tell for sure from the picture, but it looks a little dry - Masdevallias also tend need to be a bit on the damp side.

[ejramer]

Thank you, Roberta. The medium is quite dry. I was planning to water tomorrow but probably should have today. It's such a tiny pot and it dries out quickly. I'm in the San Francisco Bay Area, and I have been thinking about getting a mini greenhouse to use on my patio that would filter the light and also provide some warmth when our winter nights get below 40*F. Do you think that would be better for it than moving around? It would be a little on the cooler side overall. I could use a seedling heat mat on very cold nights (haven't bought one yet but I have an outdoor outlet that would make it very easy to use).

[Roberta]

One caution on the mini-greenhouse... it's fine when skies are overcast and the air is cool. But if the sun hits it, can heat up quickly (think windows closed in a car, or "greenhouse effect") That Masdevallia should be fine down to 35 deg F, especially since it will be on your sheltered patio (the building will radiate some heat) When it's cold, keep it a little drier (but never bone-dry, with no pseudobulbs it does not have any moisture reserve) Ideally, do your watering in the morning so that dries out a bit before the night cold hits. If you are in SF itself, or on the Peninsula, you are in a terrific area for growing Masdevallias. (When I go to the SF orchid show, and the society sales table is full of beautiful Masdies, I have to slap my own hand to not reach out and take them all home... my summers are on the warm side for them, and so my success rate isn't great though I'm finding some that will tolerate if not enjoy the conditions that I have)

[ejramer]

I am on the east bay side (Berkeley area, close to the bay) so I think it's a bit less favorable. It's very mild, but I sometimes see frost on the grass in the morning in January. I probably should put a thermometer right on my patio to measure how much warmer it is than the surrounding air

[Roberta]

Originally Posted by ejramer

I am on the east bay side (Berkeley area, close to the bay) so I think it's a bit less favorable. It's very mild, but I sometimes see frost on the grass in the morning in January. I probably should put a thermometer right on my patio to measure how much warmer it is than the surrounding air

Do check your actual temperature on the patio (as opposed to the generic weather report) ... it only takes a degree or two of warmth to not freeze the plant. My temps occasionally get down to the mid 30's F, even more occasionally close to freezing (on my patio thermometer), and I have about 90% of my orchids outside. Even when it gets that cold, it's not for more than a few hours. If we get into a weather pattern where there is serious frost for many hours over a week or so, you can bring it in - but you'l have a forecast to warn you. If acclimated - and leaving it outside as the weather cools off, it will do that naturally - orchids aren't that fragile, especially those that want to grow on the cool side.

Summer is really the bigger problem... if it gets warm, keep it fairly wet. I use clay pots, on the hypothesis that the roots get a bit of evaporative cooling.

---------- Post added at 08:40 PM ---------- Previous post was at 08:25 PM ----------

If you REALLY want an excellent reference on growing in the SF Bay area, get your hands on "A Bay Area Guide to Orchids and their Culture" by Mary Gerritsen, published by the San Francisco Orchid Society. It addresses all of the micro-climates in the Bay Area in detail and is full of examples of what grows under what conditions. If you go to an SF Orchid Society meeting or contact them, I'm sure they have the book available. (I got it for myself, knowing that my conditions are just a little different, but close enough that I can figure out the adjustments)

[ejramer]

Thanks for the advice! I will see about finding a good place to keep it outdoors and monitor the temperature. Will also try to get a copy of the book! I found it on the SF Orchid Society website with online ordering, so that should be easy.