Q: I have twenty Leyland cypress, twelve feet tall. When do I fertilize and what do I use?
A: The first question to ask is if the Leylands actually need fertilizing. Do you want them to grow much over twelve feet tall? If not, they can thrive without yearly fertilization, especially if you mulch an area four feet on all sides so roots can spread out and anchor the plants from wind damage. If you want to increase growth, use any landscape fertilizer three times per year: spring, early summer and fall.