What would cause my vincas to quit blooming?

annual vinca or perennial?

Sherrie, it could be the temp., are these under a tree? Do you have them in good fertilized soil?, You may want to look into this, and even use your trollel, and scoop some soil back, and put in new peat soil, and this may really help you. Tho remember, in hot tempt, a lot of flowers espec. in this high tempatured summer - likely are not producing. If you have this in a large pot, made with the redish crock like material, I would move it to a shaded area, for the heat of the day. Only have it in the sunshine, early in the morn, and then about 11:00 move it to the shaded areas.. if you have any. This is a very diff. yr than ever before. In your area, this yr., the temps are in the 120's, and wow this is very diff. Best wishes, J.

Some information you may find helpful:

http://mikesbackyardnursery.com/2014/06/vinca-flower/

Good Luck!