I had never heard of it either, so I looked it up on the internet. The pictures look just like C. bicapsularis, even the seed pods look identical. I found one web site that says the difference is chiefly in blooming time - C. surrentensis blooms in summer, C. bicapsularis in fall.
My Christmas cassia/C. bicapsularis is loaded with sulphur cats, as usual - personally, I'd like to have a summer bloomer so I'd have the beautiful blooms twice a year.
Sherry

Here is a link that might be useful: Cassias

Im trying popcorn cassia ( I got seeds from trade on seed trade)this year hope it works well I also have candlestick cassia but no butterflys yet this year sad....Angie

You will like the popcorn cassia, Angie. It grows very fast and the sulphurs love it. The problem I've had with them is that they seem to pretty much die off with a freeze. Some come back, but most do not. I'm in Central Florida, zone 9B.

Thanks all, I am trying to encourage my neighbors to replace a tree they lost, as this tree would be similar in size (and would attract more butterflies), and ran across this surrentensis name.
Sherry you got further than I did searching on it, thanks for sharing the link. Personally I have a small bicapsularis (I guess), bunch of bahama, and some candlestick seedlings. Also have a bunch of the invasive cassia, which is in a couple of little patches, and since it is constantly cut for feeding cats it has never had a chance to bloom and be invasive (picked a bunch of them out of the forest where it grows wild). It is such a great food resource. Once more of the little ones get going I'll be removing the "bad" ones. Anyway, thanks again everyone!