Found this out on San Juan Island in the empty crotch of a missing branch of what was likely a big leaf maple or perhaps a Garry oak (tree had not yet leafed out). Any idea? Likely a native of some sort, this was in a state park not a cultivated area.

Very cool whatever it is. The growth habit reminds me of Piggyback Plant (Tolmiea menziesii) which was a popular houseplant back in the 1970's.

I'm wondering if a type of miner's lettuce? Claytonia perfoliata. Not sure if they grow on trees.

Aha, it does look like Claytonia, maybe C. perfoliata: http://garden.org/plants/searc...

I'd imagine if seed(s) landed in the crook of a tree or rock crevice it would sprout.

Funny I didn't ever see any plants on the ground, but perhaps the local deer population has taken care of that. These crotches (found in more than one tree) were about 5' above the ground and the island deer are fairly small so maybe that's why they are growing in the trees. It just caught my eye, the green was really bright and fresh looking, like a salad in a bowl.

Claytonia was my initial thought as well.

Bonehead said:Funny I didn't ever see any plants on the ground, but perhaps the local deer population has taken care of that. These crotches (found in more than one tree) were about 5' above the ground and the island deer are fairly small so maybe that's why they are growing in the trees. It just caught my eye, the green was really bright and fresh looking, like a salad in a bowl.

Maybe a bird dropped seed that landed in the crook of the tree or maybe it was blown there by wind?