Just watered our Lemon Verbena plants in the field, and this one is a good example of what happens to a healthy plant that was pruned heavily in the process of harvesting leaves. It grows back quickly, and it produces more stems that will provide more leaves to harvest later.
The first year I grew Lemon Verbena I was very hesitant to cut the stems at all. I was afraid I'd damage or kill the plant. Now I've learned the truth - Lemon Verbena is more like a bush than a flowering plant. Once it is established, pruning it is a good thing because it promotes bushier growth.
So, take it from me, don't be hesitant or afraid to cut back your Lemon Verbena plants growing outdoors.