Q.
I also have questions regarding watering Oleanders (see attached pics). I have
2 separate hedges I'm currently grooming and both are in full sun exposure for
about 6 hrs. My lawn currently waters them for 15 min. per day and they also
each have 2 drip feeders at a rate of 2 gph each for 15 min. 3 times per day.
The issue I'm having is the leaves are yellowing rapidly and appears to be
worsening as the months go on. I did fertilize them this spring with 2 tbs of
chelated iron to the soil and 1 tbs of liquid magnesium per bush. Did I over
fertilize? I'm hoping this issue is not series as in leaf scorch. 
A. Most of the problems
on your oleander appear to be from the older growth and shading. I would prune
them differently. I would remove one or two of the largest stems from the base
of each plant, not prune at the top. You would do this next February, just
before new growth. You will see new growth coming from the base and where the
cuts are and in places where it receives light. Every year or every 2 or 3
years you will do the same to encourage new succulent growth from the base.
Continually pruning at the top of the plants, hedging, will create big old wood
at the base with no leaves. As the wood gets older, it drops its leaves. If you
want to have leaves, you have to continually renew young growth from the
bottom.
