for cercis canadensis Forest Pansy?
Can you recommend a reliable source
Magnolia Garden Nursery, 45 miles northwest of Houston, has it in two sizes
It is a wholesale nursery only. Contact a local nursery and ask if they will order it for you.
Fairweather Gardens has 4-5 footers listed. I've always had good luck with their material.
Here's the PlantScout rundown: http://davesgarden.com/ps/search.php?search_text=forest+pansy&submit=Search
I went to Greenwood Nursery last summer (I was in the area and invited myself over ;o) If they're shipping out the trees I saw, you won't be disappointed - they were very large and healthy-looking.
I picked up a ~1.5" caliper (5' or so) 'Forest Pansy' last spring from a nursery in the McMinnville area. It bloomed great this spring (before the cold snap came through and knocked everything back a month...) Good luck in your search - I think you'll really like the spring foliage on 'Forest Pansy'!
Greenwood is okay, though not always the cheapest -- it depends what you're buying, and I haven't looked at that cultivar (though I should: the generic C. canadensis puts on a show ever year here). Get a free membership from them and you get a bit of a discount on orders.
ForestFarm has always been good in my experience, though this year I have a plant from them that seems to be dead, dead, dead... the buds haven't opened, must drop them a line. It astounds me how they can grow so many things well. (Some rosarians have claimed that they've got some of their species roses mis-identified and won't listen to people trying to correct them, but that is about the worst thing I've heard: the R. sericea pteracantha [Wingthorn, impossible to mis-identify] I bought from them earlier this year has gone from buds to blooms and lots of ferny-looking foliage.)