Hollyhock and Marsh mallow

Hollyhock noun - Any of various plants of the genus Althaea; similar to but having smaller flowers than genus Alcea.

Marsh mallow and hollyhock are semantically related. In some cases you can replace phrase "Marsh mallow" with "Hollyhock", this terms are similar.

Marsh mallow noun - European perennial plant naturalized in United States having triangular ovate leaves and lilac-pink flowers.

Hollyhock and marsh mallow are semantically related. You can use "Hollyhock" instead a noun phrase "Marsh mallow".