Looks like Trapa. Here is a link that might be useful: Waternut

Thanks for the help, everyone. I now know that I have Water Hyacinth (sp?). I'll take pics of the rest of them tonight. BTW, do you know if I can over-winter the WHs in my little indoor "pond" (it has a waterfall, but no filter yet... a filter will be added very soon though)

Very interesting page; it's always fun to look at plants from a different perspective (ie, I don't fish so I wouldn't think of them in these terms); and it's nice to see pictures of local plant collections. If I might make a suggestion, though, it would be really helpful to include the Latin names as well as the common name. I just did a google image search for 'pondweed' and practically every picture on the page was a different plant; and especially since this is on the internet, what is 'pondweed' in Tennessee is probably something else altogether in Oregon, and heaven only knows what plant is called Pondweed in Australia; with the Latin name at least we'd all be thinking about the same thing. Just putting the name in parentheses after the common name would be really helpful to those of us who are interested in a more botanical sense, and it's easy to ignore if you don't want to deal with it. If you aren't sure what the species is, just putting 'Carex spp', meaning 'some species of Carex' is better than nothing. You're right that most water plants aren't included in the easy wildflower guides; they're not so easy to ID. I don't mean to be critical, I enjoyed looking at your site, but this is a relatively easy change that would be very helpful to a lot of us. WW

I have these plants from my organic garden for exchange: Creeping Jenny (a.k.a. Moneywort, Lysimachia nummularia); Lemon Balm; Helianthus multiflorus Flore Pleno (a.k.a. Perennial Sunflower); Aegopodium podagraria 'Variegatum' (a.k.a. Snow on the Mountain/Bishop's Weed/Goutweed); potted white blooming Lysimachia clethroides; Perilla (a.k.a. Beefsteak Leaf, Beefsteak Plant, Chinese Basil, Wild Sesame - when they come up in May); small bleeding hearts; tall pink Phlox; several kinds of tall & medium high fall Asters; Phalaris arundinacea picta (a.k.a. Ribbon Grass, Reed Canary Grass); purple loosestrife; Tradescantia x andersoniana (blue); orange Campsis (Trumpet Vine); burgundy daylilies with yellow centers; self-seeding blue morning glories,..... I am looking for all kinds of aquatic plants, blue or white or lemon yellow perennials or self-seeding annuals. Please see my page for details. I need the aquatic plants ASAP. I am in Brooklyn, near the Brooklyn Museum. Will travel to Manhattan.