Too Much Calcium?
 

I've had a lot of poor results in recent years when I repot from moss to Orchiata. My problem is just "failure to thrive". I use some crushed limestone in the bottom of well-drained plastic pots and I've read that Orchiata is slaked with lime. Both K-lite and MSU-RO fertilizers have been tried over extended periods (I use RO water). It's not easy to tell how much water they want because the rocks in the bottom make the pots always heavy. I don't water when I can see condensation on the wall of the pot.

My difficulties have included Phals, Paphs, Catts, and Oncidiums. I was wondering if anybody else has had this problem, and whether there's such a thing as too much lime in the pot.

I believe, if the roots aren't wrapping the limestonr, most of the dissolved minerals from them are drained by the holes on every watering.

New Orchiata holds very little water. Lots of people take a while to learn new watering habits. Try increasing your watering - maybe a lot. Use a wooden cooking skewer to determine whether the medium is still wet deep down inside.
Using skewers to determine when to water

jmrathbun -

You are not very specific about the problems you are having.

Are the plants growing new roots, or not? Staying well hydrated, or not? Blooming, or not? Same problems with all plants, or are the Cattleya problems different from Phalaenopsis problems?

If you can be more specific about why you think your plants are not thriving, members here can be more helpful.

Photos would help as well!

Details
 

Instead of flourishing -- getting bigger every year -- many of my plants are regressing -- fewer and smaller spikes, fewer healthy roots, leaves withering and pseudobulbs drying.

I think you're not watering enough. That would account for what you describe.

water
 

You may be correct. I'll try more water and see what happens. I've always been afraid of overwatering; it seems the symptoms are very similar...

Since orchiata tends to be hard to hydrate, I agree more water (really better watering) is the place to start.

At each watering flush copious water through the bark to assure the roots are getting wet. Multiple (2 or 3) flushes in a row are beneficial. Each flush should be thorough enough to wet all the roots.

You still want the medium to be dry or nearly dry before the next watering cycle. For most plants this will mean watering 2 or 3 times a week.

John, don't be fearful of "overwatering". Water, by itself, is not an issue, and you can likely water heavily and frequently - if your potting medium is in good shape.

Where excess water becomes an issue, is when the medium is too fine and dense, either through the use of too small of a particle size to start, or if the medium has broken down. In those situations, water can be held in-between the particles, cut off the free air flow to the roots, and literally suffocate them.

That is an unlikely scenario with Orchiata.

I water everyday in hot weather! Most of my Cattleyas are in medium to large grade orchiata.

To continue the above helpful discussion, a particularly stark divide has emerged in a group of Phals that I purchased nearly three years ago. Some were in moss and some in bark. Three got repotted, partly because I thought it would be good for my watering schedule to have all in the same medium. Three didn't, including two in moss and one in bark. The three that weren't repotted are doing splendidly... bloomed for a couple of years and are now reblooming on big, branched spikes. The leaves look magnificent, too, and most roots remain in the medium. The three I repotted look horrible: they have lost most leaves, bloom on shorter spikes with fewer blossoms than when purchased, and they have a lot of roots out of the pots. I use orchiata over a limestone base, MSU-RO 1 tsp per gallon weekly alternating with my usual RO water, they also get monthly Kelpmax 1 tbsp per gallon. So care is identical, age is identical, I use the same potting techniques as I have for nearly 20 years, they grow outdoors in summer and under a 400 watt HID lamp in winter where it's a bit cool but humidity remains around 60.... no difference except the repotting. What's wrong?

I believe you are poisoning your plants. It could be from calcium, but I suspect it is a general situation.

First of all 1 tsp/gal of MSU RO is about 175 ppm N. Personally, I'd not exceed 75 applied weekly, and I know a lot of folks who say 50 is the max.

Add to that the fact that Orchiata doesn't absorb well and dries rapidly. That means that you're probably concentrating the residues in the potting medium quite rapidly.

Add to that the dolomite used in the production of Orchiata, and your solution ion concentration is probably though the roof every time you water.