Not sure how much it will help, but check out their website (link below).

I wouldn't expect to see much this time of year as spring has barely sprung and most native plants are barely beginning to emerge from dormancy. They grow a lot of exotic water plants like tropical water lilies and lotus (the real reason for going, in my opinion), but they don't get going until well into the summer.

Here is a link that might be useful: Kenilworth Aquatic Gardens

Thanks, they actually don't say what's coming up on their web site, but I suppose I could call them. l saw in other places: marsh marigold, and something like trout lily, so I think things are getting going, but its possible they don't have natives.