1. Leaves toothed, most also lobed (at least some asymmetrically so)…Broussonetia
1. Leaves entire, not lobed…2.
2. Leaves cuneate to rounded at base; leaves > 1.5× as long as wide; shrub to small tree…Kalmia
2. Leaves cordate at base; leaves about as long as wide; medium to large tree…3.
3. Flowers white to yellow; capsules linear, >10× as long as wide; leaf undersurface with curly simple hairs; nectar glands present in the main vein axils on the undersurface of the leaf (visible from the underside or the upperside in fresh leaves and herbarium specimens as a triangle 1-4 mm on a side)…Catalpa
3. Flowers lavender; capsules ellipsoid, < 2× as long as wide; leaf undersurface with branched (dendritic or stellate) hairs; nectar glands absent…Paulownia
