I have trimmed around 100 Oleanders in El Paso, TX. All Oleanders in the area were affected by the rough winter weather and 3 day freeze. I cut them back to about 1 foot high because that is where the new growth is. I also clean out all debris and dead leaves from the center core. This exposes new growth to the sun. Another problem with the Oleanders is many are not being cut and people have been advised to wait and see. This is bad advice, it is easy to tell if a branch is dead because it will be brittle and break. These dead branches must be removed. The plant is trying to feed the dead branches and the new growth is suffering for it. If the Oleanders are left alone and not trimmed the dead material will attract bugs, esp. Aphids and ants which have attacked almost all Oleanders in the area. After pruning I wash off the aphids and water the plant, and then I apply a mild diluted pesticide, almost any type will work, whether organic or not. Good Luck, Jeff - Keystone Lawn Care - El Paso, TX 915-920-5333