A. Vitex, or chaste tree, is relatively pest free. It originates from the Mediterranean region where the summers are usually hot and dry and the winters cool to cold and wet.
|Vitex in winter|
The only real problems the plant has are if the roots remain too wet or the plant doesn’t get enough water. So my reaction to your question was concern about your irrigation practices; either watering it too often or not giving it enough water when you do irrigate.
Both could cause similar problems. If the roots stay too wet, root rots develop and you might see a thinning of the canopy and branches dying back. Watering too often results in poor growth or worse. If overwatering continues, you would probably see dieback in the tree and eventual death from root rots.
If the plant does not receive enough water, the plant canopy will begin to thin out and along with that a reduction in blooms. If you feel like this tree does not get much water then try flooding the area around the tree once a week in conjunction with your irrigations. If the problem is not enough water, you should see a reaction to additional applied water in 3 to 4 weeks.
|Vitex in bloom|
It also will do best with irrigations similar to other most of your landscape or fruit trees. This means regular deep irrigations.
Avoid daily irrigations. Water about twice a week during the hot summer months. In the spring and fall months, water deeply and thoroughly once in a week. As temperatures cool towards winter, you would probably irrigate deeply every 10 to 14 days.