I’m wondering if there is a way to get the leaves to drop off of my witch hazel in the fall, or before it blooms?
Some witch hazels have a habit of holding onto their dead leaves (this is called marcescence). Leaf drop (leaf abscission) can also be affected by weather patterns or by the age of the tree. The only way to get them off the tree before they finally do it themselves is to remove them by hand.
An article by Phil Clayton, published in the January 2007 issue of The Garden, mentions that some yellow-flowered varieties have this trait. Here is an excerpt which quotes Hamamelis expert Chris Lane:
A (…) free-flowering yellow selection (…) is H. x intermedia ‘Ripe Corn’. The only downside is its habit of hanging onto old leaves as the flowers open. This trait occurs in some other cultivars and is usually frowned upon by growers (…) a mild autumn followed by a sudden frost can make more leaves hang on to branches. Fortunately, as with H. x intermedia ‘Ripe Corn’, older plants often grow out of the habit.
An article entitled “Ranking the Scents and Sights of Hamamelis” from the February 25, 2011 posting in Swarthmore College’s Scott Arboretum Garden Seeds blog also includes a chart “Ranking Leaf Retention and Fragrance of Hamamelis.”