It is very easy to over water Cattleya orchids
Cattleyas need to dry out between watering
Water and wet roots are the cause of “root rot”
It is better to grow Cattleyas in shallow pots to dry out faster
Cattleya roots need to breath
These are popular orchid growing concepts and if you grow your orchids according to these concepts you can grow very nice orchids even though every one of these concepts is wrong.
There are four kinds of water available to water your orchids, Reverse Osmosis (R-O) water, rain-water, surface water, and well water. The first three are all acceptable while well water is the major problem that causes orchids to grow poorly. When Roy Tonkanaga was in Florida recently he talked mostly about the value of “flushing” your pot and he came to the conclusion that R-O water and rain water were best for orchids without really knowing much about the supportive chemistry and never mentioned surface water as he was not familiar with its use
I collect water samples in the ubiquitos plastic bottle and write the location on the bottle. I keep these in a closed cupboard in the dark to prevent poosible alge growth. The second picture is a TDS—total dissolved solids meter. What is a total disollved solids meter??? A TDS meter is just a voltmeter. When chemical compounds are disolved in water they ionize virtually 100% at low concentration levels and form two ions or electrolytes that carry a positive and a negative charge. A TDS meter has two metal electrodes. When they are inserted in a solution and the battey is turned on it measures the voltage between the two electrodes just like any voltmeter. The larger the concentraion of electrolytes in the solution—the greater the voltage. This “voltage” is then coverted into what is called ppm-parts per million of charged particles in the solution. In chemistry these compounds are called “salts” that is where the compound sodium-chloride, table salt, got its name. The following table is a selection of different water samples analysed for their concetration of disolved salts.
Ocean water—-too high to measure
Orchid Island Botanical nursery 810ppm pH 8.2
My well for sprinkling my lawn 410ppm pH 8.2
Port St. Lucie Municipal water 349ppm pH 7.2
Rob Palmer’s well 286ppm
Melbourne Municipal 314ppm pH7.6
My salt water swimming pool 255ppm
Vero Municipal water 210ppm pH8.2
Snowbird water, Utah 208ppm pH8.2
St. Paul surface water from the river 182ppm pH8.95
Minneapolis surface water from the river 178ppm pH8.92
Chicago surface water from Lake Michigan 174ppm pH8.5
Lancaster Gardens, Costa Rica 144ppm
Rainwater from rain barrel 61ppm pH7.2
Rainwater from bucket 28ppm pH7.0
Rainwater from the Bahamas 32ppm pH7.0
RO water from Publix 6ppm
The average well water in coastal areas of Florida is 350ppm plus, a few wells are better, and some are worse. Note; the well water from Orchid Island is about as bad as it gets. Melbourne water is a mixture of well water, surface water from the St. Johns river and some R-O treated water. Many cities like Vero Beach treat their worst well water with Reverse Osmosis and mix it in with the rest of their well water. The wells farther inland in Florida tend to be a little better than the costal areas. My well has 410ppm which is average for wells in Vero Beach. Palmer orchids well has only 286ppm which helps Rob Palmer be an above average grower. Surface water runs about 175-180. Rainwater from my rain barrel is higher than rainwater collected in a bucket because there are decaying leaves in the gutter which give off some salts especially a minute amount of Nitrogen. The well water in Minnesota is generally worse than the well water in Florida and the people that get their surface water from the Mississippi river have no problem, but in the suburbs, and outstate they generally have to resort to putting in their own RO system for water for their orchids.
For water to noticibly affect Cattleya growth two things are required, (1) a level of concentration of disolved salts, usually above 350ppm and (2) a length of time exposed to that level. The first plant above is the typical Florida Cattleya watered with the typical Florida well water. The lead pseudobulb has no roots yet and looks fine. The second pseudobulb has good roots which have been in the high salt “climate” a year and looks fine but from the third pseudobulb back, they are shrucken and generally twisted and the leaves are twisted. It takes one to two years, at 350ppm to kill the roots—”rot root” and cause the appearance of the shrunken pseudobulbs. In the second picture; the plant watered exclusively with rain water has all plump pseudobulbs with erect uniform leaves.