There isn't a single, specific term for when a stem grows up. However, depending on the context, you could use several terms:

* Erect: This is a common term for a stem that grows straight up.

* Ascending: This term describes a stem that grows upwards but may have a slight curve or bend.

* Upright: This is similar to erect, but can also be used for stems that are slightly angled.

* Vertical: This is a more technical term for a stem that grows directly upward.

The best term to use will depend on the specific angle and direction of the stem's growth.