I don't get it. Are you wanting to grow these seeds in these bottles? As in, two matching 'bottle gardens'? Why do you want to know what to put in the bottoms of the bottles? Aren't you going to put the seed mats in there? You could put gravel for drainage, but I don't think the seeds will do well. They will probably germinate, but if the bottles are closed, and even probably if they aren't, the seedlings will get damping off disease (caused by a fungus), and will just rot away to nothing, and you will never see flowers. To avoid damping off, you will have to use either a terrible-smelling product called No-Damp, or chamomile tea brewed at medicinal strength (at least 5 tea bags to a teapot, steeped for 20-30 mins). Personally I've never used chamomile tea, so I don't know how well it works. But using strong chemicals in a terrarium is never recommended, because they cannot be washed out.

Hi DeweyMn,
I think sahoyaref is right. It sounds as though you have one of those garden seed mats that you roll out like turf grass. Is this correct? If so, I don't think it will do very well in a closed humid bottle without ventilation. Inside it will mold. Those mats are designed to hold water like a sponge (like a chia pet). But, moving air keeps it fresh. If it does sprout it will rot (like veggie sprouts in a wet bag- slimy yuck). I hope this doesn't dampen your terrarium spirit. Give it a shot, who knows. If you do decide to give it a shot, keep with the larger texture soils like sand and some perilite for drainage and larger pebbles- lottsa air space (not water or you'll end up with a bog). YOu may have to fiddle with nutrients, depending on the plant needs. I think you should try a container garden instead. Maybe large punch bowls? That could be pretty, especially colored glass. I wish you all the best!! -ddot

Thanks for the info. I also read up a little more on this site for additional info. Had to put w.c. plan on back burner due to other projects but I'll experiment a little as suggested. Again, thanks.

I buy those mat kids for a quick picker upper for my garden. They do very well, but, the grow tall, a water bottle will not be sufficiently tall, they germinate very close together and I usually thin them out, even when growing them outside, so I wouldn't try planting them in a bottle.
Ana :)