James,

The higher humidity you will manage to maintain - the faster it will do. Ziplock bag zipped - 2 weeks. Just covered - 3-4 weeks. Just don't let it dry or water too much. Ziplocked bag doesn't require any watering - since nothing evaporates.
Nice thing to have - a tray with a high humidity dome - all suckers, leaves, starters can coexist there, you repotted something - want to give it a ICU treatment - here it goes for a week.

Irina

Here is a link that might be useful: high humidity dome

In reference to the humidity dome....I buy Rubbermaid Clear Impressions storage boxes, the small shoe box size (about 5x9x14) is about $ 1.28 at Lowes. The box is pretty clear and the lid is a little more frosted. It is high/deep enough for leaves and small plantlets and suckers and keeps in the moisture while letting quite a lot of light in. An added bonus is they stack nicely. Each one holds a lot of 3 oz solo cups. I'm growing a lot of little plants in them and it has worked well for me. Usually when they out grow this box they are ready to come out anyway and the lid comes off. Occassionally when I do need humidity for a taller plant, instead of the lid, I make a dome lid using another box. I invert it over the bottom box and tape them together on each side to hold it in place.

Oh, and last year I had ordered a couple humidity domes but I thought I could use the bottom trays I already had (they measured the same size), well they didn't fit and the water that forms on the dome just runs down onto my table top. So if you order domes, please order the bottom trays at the same time.

tish