I have a very large dual trunk oak that was struck by lightning last night. It blew off a large section of bark and has a split along one trunk about 30 ft. How can I keep from losing this tree? The effects of a lightning strike vary greatly and all you can do basically is cross your fingers and wait! You will want to try to minimize any other stresses to the tree this summer. The most common one would be drought. You might consider giving supplemental water to the tree once summer kicks in, maybe once or twice a month when there is no rain. If it is a post oak, you need to be very careful not to overdo it. Saturated soils for long periods of time are really hard on post oaks.