Artificial Lights And Winter Rest

[moniluhum]

Most of my orchids are grown in the house under artificial lights. Therefore, the temperature only varies about, at the maximum, 10 degrees if even that. What does that mean in terms of winter for plants?

[Jx3]

I grow under t8 lighting. 16 4ft bulbs total i get a 10-15degree drop in winter and have had no trouble blooming phals, paphs, oncidiums, dens, and masd. The only plants i have problems with are the cattleyas for the life of me i cant get them to bloom.

[raybark]

First of all, not all orchids need a "winter rest". Some just take a short break, then restart growing, and others are particularly active in the winter.

Those that truly do need a winter rest, need a period of no nutrition. Diurnal temperature variation has nothing to do with it, although some of those "resters" do prefer slightly cooler overall temperatures.

And, as it turns out, Dr. Yin-Tung Wang (then of Texas A&M) showed that plants that we have always been taught need a 10°-15°F drop at nighttime to initiate spikes (phals), actually need that much of an overall drop in average growing temperature for a couple of weeks to do so, not a day/night variation.

[moniluhum]

Therefore, plants that grow under lights that do not require winter rest (which require no nutrition) could flower more often because they do not have to go through the normal changes that occur during winter. Is that correct?

[raybark]

I don't know that that is entirely correct, but it seems to me that the closer to the equator the plant originates, the less seasonal variation occurs, so the same may be true for yours.

[moniluhum]

Therefore, to be safe I should withhold nutrients during the winter season on all the plants or just the ones that do not appear to be growing. Any thoughts on that?

[raybark]

If you want to be that selective, you'd be better off to not fed those that are not actively growing.