What is collective noun for stalks?

There isn't a specific collective noun for stalks in common usage.

However, you could use a more general collective noun depending on the context, such as:

* Bunch (for stalks of flowers, celery, etc.)

* Cluster (for stalks of fruit, grapes, etc.)

* Stand (for stalks of corn, wheat, etc.)

* Patch (for stalks of plants growing together)

You could also use a descriptive phrase like "a row of stalks," "a field of stalks," or "a bed of stalks" to indicate the quantity and arrangement of the stalks.