Rheum rhabarbarum POLYGONACEAE
1. Habitat, growing at edge of our yard with grass, clover, wild geranium, spruce and birch. 
2. Leaves- simple, alternate
3. Inflorescence is a panicle
4. Flowers- ovary superior 3 fused carpels.
5. Achene fruit.
6. 6 petaloid tepals
7. 6 connote petaloid tepals.
8. Stamens, 6-9.
9. Dehiscent fruits.
10. 3 fused carpels.
11. I cant tell the placentation, the seed fell out of the carpel so maybe it is free central placentation.
12. 1 seed per carpel.