Rama vs. ramo
While the Spanish words ramo and rama both relate to plants and branches, they are not interchangeable and refer to different concepts. The primary distinction is between a structural part of a tree and a collected bunch of flowers or sprigs.
Rama
A2A rama is a branch, which is a structural, woody part that grows from the trunk or a larger bough of a tree or shrub.
Un pájaro carpintero hizo un nido en la rama de aquel pino.
(A woodpecker made a nest on the branch of that pine tree.)
Tuvimos que cortar una rama que estaba a punto de caer sobre el tejado.
(We had to cut a branch that was about to fall on the roof.)
La rama más baja del manzano estaba llena de fruta madura.
(The lowest branch of the apple tree was full of ripe fruit.)
La filosofía es una rama del conocimiento muy compleja.
(Philosophy is a very complex branch of knowledge.)
Ramo
A2A ramo is most commonly a bouquet or bunch of cut flowers. It can also refer to a small bunch of herbs or sprigs, or a specific field or sector of industry or knowledge.
Mi esposo me regaló un ramo de tulipanes por nuestro aniversario.
(My husband gave me a bouquet of tulips for our anniversary.)
La novia lanzó su ramo de flores a las invitadas solteras.
(The bride tossed her bouquet of flowers to the single guests.)
Por favor, compra un ramo de perejil fresco en el mercado.
(Please, buy a bunch of fresh parsley at the market.)
Mi tío trabaja en el ramo de la construcción desde hace veinte años.
(My uncle has worked in the construction sector for twenty years.)
Summary
In essence, think of a rama as a single, structural branch that is part of a tree. In contrast, a ramo is a collection of items (usually flowers) that have been cut and gathered together, forming a bouquet. A simple way to remember is: la rama is on the tree, and el ramo is often a gift.