Question
My verbena tapien, violet blue, have been in the ground for a year.  We live in northern California and they made it through the mild winter.  They are profuse with flowers but there are nearly no leaves.  What happened.  I pinched back in early spring, fertilized and waited.  The centers of the plants were all bald and now it's hard to find any leaves at all.  I went so far as to buy new ones and put them in among the established ones.  I just wanted to see leaves.  Is is mildew?  I use drip irrigation and on these lovelies I put a riser with a circular pattern to help them spread.  It goes off three times a week now that the rains have stopped.  Could you help me.  I don't want to see them die out.  When they were first in they were exquisite.

Answer
I think that watering three times a week is too much - this plant is prone to mildew, and dislikes having the foliage wet. I'm not sure what you mean by a "riser" - is this some sort of irrigation sprinkler?  

In any case, I'd water verbena DEEPLY once every 5 days in really hot weather and once every 7 days in cooler weather - by deeply I mean a soaking where the sprinkler/soaker hose is on for an hour or more.  This will encourage deep root systems.

Right now, however, I'd cut the plants back to about 5" tall.  Fertilize again with either a liquid fertilizer or a time release such as Osmocote Indoor-Outdoor.  If you think they look like they have had mildew (powdery grey coating on leaves or stems) or have crown rot (blackened stems near the soil level) you could try spraying with either Green Cure for Mildew or Serenade for the crown rot.  

I think that too much water is the culprit here - a deep soaking less often is usually better than a little frequently.

I hope this helps,
C.L.