S/H for cattleyas ?

[Dorsetman]

Global warming ?

Last year in UK we had the longest warm and sunny summer since 1976. This year so far has looked set to follow, and the latest long-range forecast from our UK met' office 'threatens' 3 months of unusual heat to come...I can keep the greenhouse to a max of about 35˚C., but no less with my present set-up, in these weather conditions. ( usually about 20˚C. at night.)

I am having difficulties keeping my cattleyas properly hydrated - I fear overhead watering with a spray or rose on my watering lance ( water lodging in new growths is not too clever ..) I find some new growths shrivelled and burnt up - It takes me several days to water every pot ( about 500) by dipping etc, and I have only an hour or two per day to look after all my orchids .( I am the carer for my wife, who may be in her last days... I won't say more ).

Humidity is fine, 65-70% by day, and upwards of 90% by night, but still they are too dry - I suppose.....

They are potted in either straight bark, or those repotted over the last 12 months in bark/rockwool cubes mix, or those repotted in the last 2 weeks or so with an addition of shredded sphagnum moss. Maybe those mixes will be an answer, but maybe not.

I have done well growing oncidiums and many other genera in S/H in the past using an inert mineral compost - "baked clay pebbles" and think to try this with my cats. The trays of water, an inch deep, will surely lower root temperature, and could keep them wet enough. But what about resting ? How to keep that bit of moisture which they seem to need ?

Any experience, actual, not theoretical, please ?

[Sheryl]

Sending hugs Geoff.

[raybark]

I have grown lots of catts and related genera in semi-hydroponics. The key is moving them over just as the plant is actively growing brand new roots, as the existing root system will take the move poorly.

As the inventor of the technique, and the person with arguably the most experience with it, I am quite sure any plant can be grown that way, but I am equally certain that does not mean any person can grow any plant that way. "Semi-hydro" only defines the use of an inert medium and the use of a static reservoir to deliver the water. There are a great many more cultural parameters that determine an individual's success with a specific plant.

In my warm, wet greenhouse in Pennsylvania, I was never successful with hard-cane dendrobiums, while others will tell you they are the ideal beginner plant for the technique. I had a customer in Delaware who won all sorts of awards for her cacti, succulents and caudiciforms grown that way....who would have guessed?!?!

A shot in the dark here, Geoff: is your calcium supply sufficient? Your description of the new growths pushed my thinking inthat direction for a moment.

[Dorsetman]

Thank you for the suggestion Ray ; any kind of deficiency/imbalance had not occurred to me. I should say that it is only perhaps 1 in 10 or 1 in 20 plants showing this, and some of them have several growths, only one of which is like this.
However, the fertiliser mix which I am adding to very low EC water ( good rain, or RO water) is one dveloped from the MSU fertiliser as discussed in the AOS mag, - June 2003.. The developed formula is :-

11, 8N + 2,7K2O + 11, 8CaO = 3, 5MgO + 4, 8SO3 plus trace elements.

The N is not urea, and is intended to be fully absorbed. Bark, which is my present basis is fairly rich in Calcium and I think is released as the bark breaks down, if the pH is correct. My fertiliser/water solution usually comes out at about 6.0 pH when the EC is 600µS and if not is corrected to lie in the 5.8-6.3 range , with dilute phosphoric acid or potassium hydroxide as the case may be.

Everything else in the greenhouse is growing well ; but a thought, despite what I have said about humidity; the other benches have been covered with polycarbonate sheets to present a flat surface ( slightly sloping for drainage) and are covered with capillary matting, fed with water by micro-drip jets every few days to keep them fairly damp - and perhaps keep the roots cooler too.
There is no doubt that the cattleya bench is a lot drier ; it always was when I used metal ballast lighting which inevitably provided heat too ; I had thought that switching to LED would be an improvement, but not noticeably so, I find.
I have been toying with the idea of using the cap[illary matting trick on the cattleya bench.
Those other benches grew plants well but with poor flower count until I realised that my enthusiasm for hanging plants over them, meant poor light ; this does not happen with the cattleys which have supplementary lighting . So I added supplementary lighting to the side benches ( sun-blaster strip lighting) and now they too are flowering well.

[raybark]

Thank you for the suggestion Ray ; any kind of deficiency/imbalance had not occurred to me. I should say that it is only perhaps 1 in 10 or 1 in 20 plants showing this, and some of them have several growths, only one of which is like this.
However, the fertiliser mix which I am adding to very low EC water ( good rain, or RO water) is one dveloped from the MSU fertiliser as discussed in the AOS mag, - June 2003.. The developed formula is :-

11, 8N + 2,7K2O + 11, 8CaO = 3, 5MgO + 4, 8SO3 plus trace elements.

That would likely rule out a calcium deficiency.