Certified GKH Gardening Expert
This is a sign that the plant is ill. Is the lower stem firm or soft?
If it is soft, this indicates that rot has gotten into the stem. This is often caused by standing water or too much water. It may also be cold damage. Have you had a bad winter where you are? If it smells fishy, it may be bacterial soft rot. Unfortunately, there is no cure for soft rot.
If it is firm, you may have the start of a fungus infection. Treat the plant with a fungicide.