In all the years that I have grown cattleya species, there is no one rule that applies to all of them. The general guide of reducing water in winter is because pots take longer to dry in less sun and cooler temperatures. So watering times are extended for this reason. Ray is also right in that less sun (and no active growth) means less feed. David is also right in that all variables must be taken into consideration in your grow area.
You have to watch each plant and know their cycles, which may differ even within the same species. This is especially if you grow them under constant lights (like me at 12 hours in winter). I water my plants throughout the year and never rest them. I just let them dry one or two days longer.
My general home growing guidelines are these:
1. plants that are in active growth requires feed and water, no matter what time of the year. Jenmanii and warneri grow through winter. Trianae, warscewicziis and lueddemaniana may start as early as late winter (Feb/March). So watch new growths and water accordingly. Good nitrogen is essential for strong growths and good light (even in winter).
2. when growths mature, there are two ways to treat them:
a) for winter growers, they usually flower straight away in early spring so must have constant water and feed to maintain flowers, rooting usually after flowering. They will usually rest through summer with regular watering and less feed (roots dry in between).
b) for summer growers like labiata, schroederae, maxima, dowiana, eldorado, bifoliates, violacea, percivaliana, mossiae, and trianae (second growths), water and feed well till fall, then pull back feed (to once a month) but regular watering (after they dry 1-2 days). They will trigger blooms themselves by the amount of light and darkness. Labiatas will flower in Sept, jenmanii in Oct, maxima in November, percivaliana in Dec, trianae in Jan, schroderae in Feb, etc.
3. Dowiana, walkeriana, nobilior and most bifoliates will flower as soon as growths are maturing in the middle of summer. These need a good drying period in winter (**very important to let dry 2-3 days if no active growth or roots will rot very very easily) and almost NO feed (until new growths start in early spring).
4. I spray my plants almost every day throughout the year, esp sunny days and early (before 12 noon) but they dry by nightfall. NEVER leave wet leaves on Cattleyas or they will rot the new growths (even if the water isn't visible on the new growths). Increase air circulation if you have to.
TIP: During spraying a thin mist is on the leaves and pot surface, but I spray a little water stream on the inside of the pots (trickle down the inside of the pots) so that the roots grow in to find the water.
Since most of my plants are on semi-water culture (little water tray under each pot), the roots look downwards to find the water instead of wandering outside (the occasional wandering roots are guided back into pot with a tag push from the sides).
TIP: You can put a little moss below the new growths to encourage roots to go into the pot (if you find them wandering way too much).
5. If in doubt to water, DON'T! Better to wait a day or two. They can tolerate dryness in medium than too wet.
This is my method. Hope it may help shed some insight.
