What's the deal with dormancy?

[Butters]

Hi, all.
I keep hearing about winter dormancy. My question is about dormancy in orchids, especially in sub-tropical/tropical areas. For instance, I'm in sunny South Florida where there isn't really a winter (our seasons seem to be hot and less hot.) Unless there is a legitimate cold front coming through, temperatures where I'm at don't really get below 60 at night.

Do they still need a dormancy period? How would I know if my orchids need dormancy? A lot of them are putting out new growth of some kind.

Thank you.

[Subrosa]

Some do, some don't. Some need a cooler dormancy, some don't. You're going to need to be more specific.

[Ray]

Originally Posted by Subrosa

Some do, some don't. Some need a cooler dormancy, some don't. You're going to need to be more specific.

Spoken like a true orchidphile ...

Orchids are "niche" plants; their needs have evolved to what was available where they happened to land. Regions with distinct dry seasons, when food is less available to the plants, has led them to survive by going into a period of dormancy.

Relocating them to an environment that doesn't have those same conditions - even if it's to a semi-tropical climate we perceive as an improvement - is actually an increase in stress on the plant, so we try compensate by artificially adjusting the conditions as well as we can.

[Salixx]

Just for further perspective, there are many places where the climate and zone is considered "tropical dry." For instance, if you go to the USVI, they have deciduous trees that drop their leaves at certain times of the year- the dry season. They are going dormant just as the trees where I live in New England drop their leaves and go dormant. However, they do so for different reasons.

This is where knowing your plant helps. Those from tropical dry areas may not need a temperature differences but, instead water differences. Some many need multiple environmental changes, I.e. Water restrictions and lowered temp.

*edited for poor gramma and spelling and auto correct errors (thanks iPhone!)

[3rdMaestro]

I agree with salixx. Get to know your plants. You say they are still putting off growth? What kind of orchids do you have? I know for me, I have some dendrobiums that will continue growing as long as conditions permit but without the dry winter, they won't really bloom (at least for me), they'll just keep growing. By contrast, a catasetum needs a distinct rest or else risks death. If you don't know what orchids you have, maybe post a picture?

One other thing, depending on the orchid, "winter rest" doesn't necessarily mean cold. It may mean dry

[Butters]

I have a MaxillariaTenuifolia, Encyclia Tampensis, Phal Champorensis, Iwanagara Appleblossom, a noid Phal, a noid Dendrobium, a Brassocattleya binosa x .ttl stars, a Cattleya 'Hawaiian Flare', and an angraecum 'Mark Aldridge.'

Would any of these need a dormancy period? (Maybe this is how I should have started it. Sorry guys, I'm still learning.)

Ray, that makes since. Even in South Florida there is a well defined dry season.

I didn't even think about it being a a stressor for them. So used to creature comforts that we have that I just assumed (you know what happens when you assume...) that's all they would need.

[WalkingHorse]

As has been said, "It depends". I highly recommend Florida Orchid Growing - Month By Month by Dr. Martin Motes. Very readable and written from the perspective of an orchid grower in southern Florida.

[Roberta]

Just looking at your list, the only plant that could have even "semi-dormancy' is the Dendrobium, and that depends on what kind. If the Den-phalaenopsis type (which is a good bet) it doesn't. The Angraecum could probably use a bit of reduction in water but doesn't need it (I looked it up, actually Angcm. Memoria Mark Aldridge) and its parents are from the warm, wet part of Madagascar. But just in general, in winter when days are shorter and a bit cooler, things just don't dry out as fast, so reducing water to match the rate of drying is what you would want to do anyway. But none of these look to me like the ones that want drastic change. If one of those cold fronts is forecast, don't water! An orchid can survive a cold jolt if it is dry. Cold and wet is bad news.

[Leafmite]

If you get any cool, wet weather, be sure to use a fungus preventative on the Angraecum (unless you are already dosing it with extra Calcium). They tend to be rather prone to fungus attacks during cool, rainy weather.

I agree, though, with what has been said. None of what you have appears to need a winter rest if the Dendrobium is a Phal-type. Cooler temperatures mean that the medium and leaves do not dry as quickly and fungus can flourish so you just need to keep that in mind.

[Ray]

Originally Posted by 3rdMaestro

One other thing, depending on the orchid, "winter rest" doesn't necessarily mean cold. It may mean dry

I'll take that a step further - as I've learned from semi-hydroponic culture, "winter rest" doesn't actually mean cold or dry, it means no nitrogen.

With plants in S/H, folks are successful when allowing the pots to dry, or when watering normally, but avoiding all fertilizer until new growth resumes.