I don't really have much to add here, I don't grow barkeria. However, two things come to mind: roots being as not massive as they are can get their nutrients from the pbulbs without harming the plant. Also, according to my boss (one of the preeminant horticulturists in the mid-atlantic region), roots dont ever stop growing even during the winter dormancy (which is why they often recommend planting broad leafed deciduous trees during the fall. growing roots + no leaves = minimum stress on the plant during establishment, though given what people do catasetinae seem to be the exception i suppose). So if I'm to hazard an educated guess (and thats all it is) I'd say wait until you get new shoot growth.

Just to confuse you, I am going to advise the other way.

Roots are the main source of new nourishment and the sooner they get their own and not take away from the rest of the pseudobulbs, the better for the plant as a whole.

Just to be clear, I only mentioned the Barkeria as an example. Another plant that just came to mind is my Dend delacourii. That one is totally leafless and has been kept completely dry all winter. When I took a look into the pot today, I could see lots of new, white roots. If it behaves like it has in the past, it will probably be a couple of months before I see new growth.

K

Well try this one on. Root growth will end up being more extensive and efficient if it is somewhat starved at first. Based on that I would wait for new growth rather than new roots as the sign to resume regular fertilization. Notice I said 'regular' fertilization. I don't know that the odd low concentration feed during the winter is a terrible thing. Most orchids in nature spend their winters with the roots in contact with low concentration feed.

H

Some of my hybrids catts stop growing pbs and leaves in the winter but roots will grow like crazy so I still fertilize. The way I see it, growth is growth, regardless of roots or leaves. They can canabalize and get their nutrients from older growths but maybe they'll grow better if they don't need to.

I fertilize every other watering throughout the winter with a balanced fertilizer - 1/4 tsp per gallon of dyna-gro 7-9-5. Though I have not grown any of what you've listed, this has not proved detrimental to any cym, onc, brassia, tol, catt, laelia, zygo, phal, dend, paph hybrids, or cym species that I grow.

Don't know if that helps, but it's my experience and perhaps you can use it to weigh your options.

Steph

Interesting question Kevin. I have the exactly opposite situation, where I have new growths cannibalizing old pbulbs until they're actually turning brown and drying up, with no signs of root growth. To water or not to water..hmmm

Doesn't new growth of roots signify that the plant is ready to seek out more moisture and nutrients? That it's getting enough light energy from it's leaves to be ready to compensate with more with water and nutes? That's how I reason...plus I've seen alot of root growth ever since i started using lights, which never used to happen in the winter...so I just keep fertilizing and watering and they don't seem to mind!

May I point out 2 more things?

1. As it IS in its winter dormancy, watering should be at a minimum anyways, which means fertilizing really shouldn't be done to begin with. Compared to shoots and flowers,roots don't take much energy at all to create (evidenced by my point about roots growing on trees even when the tree has no leaves) Ergo feeding really not necessary at this point
2. I dont really think starting now vs march would amount to much difference considering how little energy the plant is using/needing at this point (see root energy from point one).

You make a good point. It really surprised me to see the root growth on the above mentioned Dend since it hasn't had a drop of water for a couple of months. Maybe a misting now and then, but no water to speak of.

K

I agree with terpguy and Howard. Green growth signals the use of nutrients. Start to feed. Roots are better left underfed.

Dirt plants will form larger, denser roots when they must seek out nutrients. Bigger root systems, better plants. New leaf growth calls on nutrients in the soil or in the case of orchids, older bulbs.
Over fertilized plants have smaller, weaker root systems.

I do not fertilize roots, only new growths.

Jane