[kmarch]

The myth: To get your orchids to flower, put them in a dark basement for the winter.

Over the years I've heard 3 or 4 different versions of this myth. Some say to put them in a paper bag (sometimes with an apple) under the sink for 3 months or 6 months.

I'll start by getting the obvious problems out of the way.
1) "Orchids"....what orchids are we talking about here? Phals? Mormodes? Pterostylus? My mixed collection? I have 12 different genera, should I chuck themALL down the cellar? Any time someone says, "orchids need..." or "orchids want..." or "to get your orchids to..." the warning bells should go off and a giant sign should flash through your brain that says: WARNING!!! OVER GENERALIZATIONS AHEAD!!!
2) While orchids are found in nearly every climate (except the Arctic and Antarctic) none of the orchid inhabiting climates experience complete darkness for an entire winter. Thus in the wild no orchid would experience 3 months of complete darkness. It is true that some orchids loose their leaves or in some cases all leaves and stems appearing above ground. Pterostylus, an Australian native terrestrial dies off in spring and survives underground only as a small tuber for about 6 months over the hot dry summer months only to emerge in Autumn when it is cooler and the rains start to fall. One could argue that this plant experiences 6 months of darkness underground. The catch is that this orchid has developed in a highly specialized way that enables it do do exactly that, to survive underground as a little corm during the dry season. The orchids that make up the vast majority of our collections do not posses these specialized structures which makes them ill-suited to survive months of complete darkness.
3) This myth overlooks the fact that many (most?) of our orchids flower...in winter! Many phals, dendrobiums, coelogyne, cattleyas/laelias, paphs, phrags, etc., etc. all flower in winter. Having them in a bag in a dark basement is more likely to interrupt their flowering cycle than it is to initiate it.

As with most of these myths, if you dig deep enough, get past the inaccuracies, over generalizations, glaring errors in logic, and simple lack of knowledge about orchids, you can usually find a few grains of truth. Fundamentally this myth is about initiating a flowering cycle. Every orchid has what I call a "bloom trigger" which, simply put, is that which causes the orchid to initiate its flowering cycle (e.g. spike). Because many orchids flower seasonally it is difficult to tell if there is one specific trigger like temperature alone or if more then one trigger operates together (like temperature along with rainfall or day length). There are 2 (possibly 3) bloom triggers at work in this myth: 1) temperature - i.e. the cool basement, and 2) light - that somehow dark triggers flowering, and possibly 3) reduced water - i.e. a cool dry winter. Let's look at these factors one by one:

Temperature: Some orchids' flowering cycles are triggered by temperature events. We know that many phals' spike in Autumn after receiving a diurnal temperature variation of 10-15F. Australian native dendrobiums flower in winter when it is cool. So temperature is certainly a factor in some bloom triggers.

Light: Although I know of no study that has been done that actually verifies that day-length/night-length serves as a bloom trigger I believe it is generally accepted by the orchid community that length of day/night does indicate to the orchid that a seasonal change is at hand thereby initiating a flowering cycle. I regularly hear and see it written that when growing under lights, the length of time the lights are on should be shortened in winter and lengthened in summer. I've done this myself when I grew under lights. And I have never heard a single dissenting voice except to say that it's probably not necessary for orchids that come from the equatorial zone where the day/night length is nearly the same year round. The belief is that longer days in summer trigger vegetative growth: more light = greater ability for a plant to produce energy for itself and that shorter days signal the end of vegetative growth and the start of a flowering cycle.

Reduced Water: Again it is true that some orchids experience a drier winter than summer (thus cooler temps happen along with drier conditions and shorter days) and that some commonly grown orchids (e.g. nobile-type dens) need this drying out (not giving them this can result in heavy keiki-ing rather than flowering). But again this is suggested as a possible bloom trigger for some but not all orchids.

As is the case with all the myths we've looked at so far there is a bit of truth in nearly every aspect of this myth but those kernels of truth have been inundated with gross over generalizations and misapplications, not to mention a fundamental lack of knowledge about how orchids really grow.

Conclusion: Myth Busted

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If you have an orchid myth you'd like me to examine, please PM me through the forum.