To dry hydrangeas, place the cut stems in a vase or pitcher with no water. Make sure they are not too crowded, and will get plenty of air-flow. They should dry naturally in a few weeks. If you have hydrangea bushes, it's best to let the blooms dry outdoors, right on the stems. Wait until the blooms have darkened, and have a paper-like appearance. Cut as low on the stem as possible.