Q.Filling a decaying limb on crape Myrtle
I have a large crape myrtle tree that has a limb ( 5″ in diameter ) that has a hole in the bottom and one about 5ft above it. The section in between is hollowed out. I have filled the bottom whole with concrete and I need to know if I should just fill the hole at the top or fill the complete voided area from the top hole to the bottom hole?
Filling cavities with concrete is an obsolete practice in arboriculture. Research since the 1970s and a long record of experience has shown that there is no advantage for structural integrity or physiological reasons, it won't strengthen the limb, and it won't promote healing. If the outer shell wall is very thin and you fear breakage, there are other ways to strengthen the area or restrict movement of the limb that might precipitate a break. Arborists sometimes use bolting and cabling, and in rare occasions, mostly for aesthetic reasons, use aerosol expanding roofing foam to fill a cavity. This material will bulge out as it expands and dries, but you can shape it with a knife and paint it to blend.