I usually mix the soil first to hydrate it. I use Promix all the time. I wouldn't worry too much. You could open the jugs on a rainy day or I use a spray bottle and spray down the top of the jug every few days. If it's extremely dry this spring we will all be opening our jugs and watering but the way the weather patterns have been this winter I think germination should happen as normal.

I would bottom water them when they thaw.

ishareflowers has it right. You need to bottom water in this situation. The easiest way I know is to use a couple of big catering aluminum foil trays. I make slits about 1.5 to 2 inches up on the two long sides. Then I sit my containers in the trays and add water. The slits mean the water never rises high enough to float the seeds off the top of the soil. I can see when the water is absorbed and rotate to the next set of containers.

I also use such a tray to group my smaller containers (12-16 ounce plastic cups for longer tap root perennials) from the beginning since 1) they dry out easier and 2) it keeps the cups from falling over (if the tray is full).

I used to wonder why people were pre-wetting their mix before filling the containers. Last year I found out why after I got some potting mix that was bone dry. In previous years the mix I got had the perfect moisture content to use straight out of the bag to fill my containers. It had just enough moisture to allow it soak up the water from top or bottom after I filled and tamped it down in the containers. When peat is too dry and light in color it is very hard to wet it and water runs right off the surface.

With mix that is too dry right out of the bag I put it in a large storage tube, spray it with the sink sprayer, then mix it in with a garden cultivator. It is amazing how much water it takes just to get the mix to that darker and slightly damp but still fluffy state that is perfect for filling the containers.

I concur that bottom watering is the best way to get them damp now although it will probably take a long time. You can tell by the color change of the mix through the side of the jug when it is wet enough. Also they should feel quite heavy for their size. Top watering is likely to just displace the seeds and then run down the sides again.

I've never tried bottom watering a container, so forgive me if these follow up questions are ignorant...

1. Is this something I can do outside or do I need to bring the jugs in where it is warmer to do this?

2. When you say it will take a while, how long? A few hours or a few days?

3. If it happens outside and takes a few days, I may not be able to avoid having then in water during overnight freezes (the jugs are at the school, not my home). Will it be a problem if the water they sit in freezes and thaws while they are being bottom watered?

Hi Emc, the first thought I had was to bottom-water as well. It is probably better if you bring them inside to do this, although it might eventually happen outside once the weather warms.

The warmer the water and the potting mix, the more absorbent it will be and the faster the mix will hydrate. In fact, I would fill the flats with warm tap water, and maybe put them in a sunny spot to get some solar warming. This process may take a few days, maybe even longer.

You could water them from the top with a watering can that has a tapered spout, but this could slosh the seeds around and it will be messy. You could also spritz them with a pump sprayer too, although that still could slosh the seeds around. Seeds have a tendency to get washed down the sides of container, although if you press the mix down firmly all around the container or sprinkle a little sand on top of the mix after sowing, this tends to better hold the seeds in place.

Use warm water whatever you do. Peat moss absorbs warm water much faster than cold.

I am really not sure how long it would take to bottom water them. I guess it depends on exactly how dry they are and the water temp as terrene said. When it is bone dry peat is hard to wet, but when only slightly damp throughout it soaks it up readily.

I would just experiment with a few jugs to see what is the easiest way to get it done. I would hate to see you drag them all indoors unnecessarily. A few days to figure out what works the easiest won't hurt anything.

When I start watering my containers in spring I never bottom water because it would be a pain with my set-up. I sometimes use a mister on the end of a watering wand and stick it into the hole of the jug for a few seconds. I also just use a gentle shower setting on the watering wand and keep it moving over my jug area to give enough time for the water to soak in without flooding the surface and washing away the seeds. That is what happens when it rains anyways. But the jugs are never bone dry when I water this way so I don't know how well it would work in that situation.

Right now we actually have some snow cover here so I don't have to worry about watering yet, than goodness.

Had several dry containers that my kids did last year. When I looked over their finished work (they wanted to do everything on their own) they didn't have the soil moist. If you have snow right now, and what I did with this problem last year, is to have the kids put snow through the opening of the milk jugs. They really had fun with it. Worked very well last year. The snow slowly melted and moistened the whole container. That's how I "water" my potted trees and pots in the hoop house during the winter.

^^^ That's a great idea, less messy and the kids could have fun! If the jugs weren't taped they would be easy to fill with snow. But even then the kids could stuff snow down the spout. If the containers are in the sun they'd probably warm the snow up to melt faster.