Seasonal temperature variation

[whitepine84]

Good afternoon,

I live in Minnesota and currently there's a good stretch in the forecast where the temperature will get down into the low 50's and 60's. I'd like to leave my plants outside for a while so they are exposed to some lower temperatures to hopefully help them flower. How long do I need to leave them out, and how cold is too cold?

Additionally, which orchids would benefit from this? I was planning on my Dendrobiums but I also have some Maxillaria, Bulbos, and phrags.

Thank you!

[Ray]

To the best of my knowledge, none of those rely on "delta-T" to initiate spiking.

While some might be able to tolerate it, I have never (intentionally) allowed my plants to ever go below 50°F, and prefer to keep them at least five degrees warmer.

[Roberta]

Even for the Dendrobiums, depends on which ones. Nobile type, lindleyi, speciosum, kingianum, and probably most of the deciduous ones from the Himalaya area and south-west China might benefit, but there area plenty of Dens from more tropical areas that don't need or want that chill. Time for some research... when in doubt, better to err on the warmer side. (Better to miss the flowering than to kill the plant) Especially since in your area, Mother Nature can surprise with more than forecast cold. Down to the mid-50's F likely is OK for all, but lower than that, some caution is in order. Especially since it is sudden - many orchids can adapt to cold with a gradual cool-down, but are likely to resent a sudden jolt of cold.