Not only does the leaf blade have an identifiable shape but the base of the blade where it connects to the petiole also has an identifiable form. The American Hosta Society cultivar registration process designates 4 possible leaf base shapes.

Tapered Leaf Base -In this case, the sides of the leaf blade blend straight into the petiole.

Flat or Truncate Leaf Base - This refers to a leaf bottom that is straight across and flat.

Rounded or Attenuate Leaf Base - The bottom of the leaf is curved and converging at the petiole.

Cordate or Heart Shaped Leaf Base - The bottom of the leaf has two equal lobes that join at the petiole. When this occurs on nearly round leaf blades, there may be overlapping or folding where the leaf blade and petiole join together.