Bill, when I was in CT, we used a newsletter that was very effective. We'd do it quarterly, but it was a quality newsletter. I put services that I would be offering the next quarter and explain them in easy to understand ways, (de-thatching, aerating, different fert apps, landscaping) If I had a real nice landscape job, I'd feature it and give address, etc to go check it out, You can throw a joke or funny picture or something to keep intrest, I would advertise for my families other business' with coupons. The possibilities are endless. Frequently asked questions is one I think I'd put in there now.
Good Luck and let us know how you make out.