Easily-confused!
If your specimen has stem/leaf arrangement:and the leaves:then you have:
╟ alternate are ♤ heart-shaped except for a __ flat-base, and
stem interior=​cham­bered with periodic diaphragms like bamboo
lookalike Japanese knotweed  Fallopia japonica
are ♤ heart-shaped with a ∪ rounded-base, and
stems are woody
lookalike eastern redbud  Cercis canadensis
╫ opposite taper at both ends, and
pass the dogwood leaf test
lookalike flowering dogwood  Cornus florida
are ♤ heart-shaped with a ∪ rounded-base this plant, please continue below …

Verify with Google images.

Learn more about hardy catalpa Catalpa speciosa

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