solid when dry soft when wet???

Sounds like a thin layer of cardboard with minimal binder, if need be i suggest making your own paper mache for the task, and depending on how small the seeds/plants are you could thin it out by sanding/cutting.

I recently was given something very similar to this, a sheet of cardboard about the size and shape of a beer coaster, which contains seeds for a lemon scented bottlebrush, simply plant the paper, keep it wet and watch it grow.

Hope that i've been of some help.

You can also use water retention gel that is sold at florists and garden supply stores . When dry, the gel is in the form of small hard drystals, but when wet, they're gelatinous . They also come in attractive colors, so that's an additional benefit for ornamental purposes .

Use a sponge, i would say

cow manure...

You must have considered old/used newspaper already. I pull several hand fulls, of same day issue, out of convenience store garbage can for my worm beds. (they are to lazy to recycle) Price -vs- aesthetics?

There's an Aussie firm that manufactured "camping toilet paper" that was impregnated with seeds for native bush. (Like wattles and Teatree) It won an "inventors" award over here, but took the inventor a little time to convince the toilet tissue manufacturer to make the special run of this product.

This stuff was highly stable until it encountered water.

"YATES" distribute "seed tape" for small seeds like carrot and spring onions to assure even plant spacing. They use a paper like carrier in that system also.

Another group involved in roadside soil stabilisation use a spray on mixture that is very much like PVA adhesive to hold seeds and mulch inplace during germination.

Cardboard (or any medium) with a weak binding agent seems like the most practical way to go I guess. What are some normal binding agents? What would be a super water soluble binding agent? Remember I can't agitate to get the binder to fail so it would literally have to fall apart with added tap water.

water retention gel seems like a very interesting idea. I googled a little bit about it. I don't really want the expansion though and they're sold in chunks not a thin solid sheet. If I apply heat or something to them you think I can reform them into a thin sheet? I really like the idea of getting a gel after watering and the colors would actually be nice.

Any other ideas in the direction of solid turning to gel with added water could be awesome...

Thanks to everyone for the help!!!

I suggest investigating water soluble paper used for maintaining inert atmophere between pipe sections during welding. After the welding is complete, the paper is flushed away. The material is inexpensive and works well.

Sounds like you need to look for an appropriate sponge.

clay

Peat moss? You may have seen the compressed discs used for sprouting of seeds...

You need to determine the optimum PH for germination & fast growth.

Polyvinyl alcohol is a water soluble polymer that is available in sheet form. It can also be purchased as a liquid at any marine supply store. You could take the liquid and cast a thin film.

I think this has already been done.......it's called peat moss.....hardens into nearly a brick when dry, then expands and softens when wet......and you don't have to manufacture it.

Do you need the seeds to stay "dry" until they reach the destination?

I have germinated small seeds and very delicate cuttings in AGAR film, or even gelatine.

The seeds can be suspended in the material and do not move. You can very precisely place them in whatever spacing or pattern that you wish. They can germinate and grow from the medium and also push roots into the soil/mixture below. The gelatine sheets could be any colour or flavour that you might like to use. (You could use vegetable dies to colour the material [I want royalties if you use this idea.] but that might influence the leaf colour for a small time as the die will be absorbed.)

The drawback though is that the seeds begin absorbing water from the time they are placed into the material and will then germinate/sprout based on the time/temperature relationship for the species involved.

Gelatine is very cheap, no dangerous byproducts and readily understood by your staff, customers and anyone else interested.

Thanks everyone for the diversity of ideas!!!

I've just set up a table full of a bunch of tests. I'll let you know how it goes. Seems like the simplest solution is some kind of medium with a simple binder. Simple is always better I guess...

The seeds have to stay dry until they are received.

Thanks again!!!

Rice paper?

So just to update in case anyone is interested. I've been trying different things. Clay seems to work pretty well. I've used it as a binding agent in peat moss and fine perlite. I think that it will work well like this. Also PVA works. Anyone know where I can get PVA that is clear or white in color? The PVA that I've been playing with is just mold release that I got from Tap plastics.

I've got a lot of options now, just need to see which will be best.

Also I want to try rice paper that seems pretty simple and awesome.

I have a pack of those soluble welding sheets in the mail that I should be receiving soon, so I'll let you guys know if that works too.

I'm gonna have to start looking into how base vs. acidic these different things will make my water. Any ideas on that? How can I easily test ph, can i just grab one of those pool tester things? Clay is base I assume? Peat moss is acidic? What is PVA?

you've got the peat ph right.

Clay really depends on the source...

a Simple Soil test will give a good general indication of the water soluble run off of different soils... http://www.planetnatural.com/site/xdpy/sgc/Soil%20Care/Soil%20pH%20&%20Test%20Kits

What ph are you looking for?

looking for ph 7.0ish not too worried about it though. I should be able to adjust with an additive pretty easy.