Yes - the leaves of the different hydrangea varieties will tell you if they are from different species such as the oak leaf, the smooth leaf or the big leaf but the leaves will not tell you as easily about the different varieties - such as a lace cap or an Endless Summer. In general the bigger the leaf the more likely it will need afternoon shade and more room. The smaller leaf hydrangeas can take more sun. You may be able to visit a large nursery or garden center with a leaf sample and try to match up your foliage to the named plants at the nursery. Don't worry  too much however. Part of the fun of gardening is the surprise factor and once your gift hydrangeas bloom you can move them (hydrangeas transplant easily in early spring) if necessary and the type of flower will make it easier to figure out the name of the varieties you have. Keep growing, Marianne Binetti