I've found that the more knowledge I've shared with a client the more they recognize the limits of their DIY abilities. This came up with one of our regular clients when he told me he'd bought a chainsaw. I asked him about whether the store he bought it from sold him the necessary safety gear, then about how he sharpens it. He asked me what he should have in the way of PPE and how to sharpen properly. After I explained it to him, he gave me the chainsaw and said, he'll just call us when he needs to get something done! That saw is sitting in my basement.
As the new owner of an existing business, Royce, you need to educate your existing client base as to who you are and why they should continue to rely on the company for the tree care needs. But what are those needs? Do they really know what they are? Not likely. There's all sorts of info you can share. Tons of material from county extension offices, ISA, TCIA, Forest Service, etc. Setting up a quarterly newsletter is a great step. Tie the timing of them into when they should be starting to look at different aspects of caring for their trees. It's January going on to Feb, your newsletter at this point could cover the stuff they could be doing right now and then prepping them for what needs to be done in the early spring (They're selling spring fashion in the stores now not winter).
Did you introduce yourself in the first letter? How many responses? How many pieces were returned undeliverable? Take that first step in "scrubbing" your contact list. That's not to say those addresses are no longer any good, someone's living there, but that it's not the right info attached to that name. Do some leg work to find out who is actually at that address. Start with a Google search see what name comes up. You may have to go passed the first page but it's likely there. Why? People will more likely open up a piece of mail with their name on it. Once you've cleaned up the list then send out another mailing with more info about you and your business, changes you may have made to improve service, like a quarterly newsletter to provide them with information about trees, tree care and any news that might require a heads up, like, a new pest infestation that is coming your way. Ask for their permission to send it to them and how they would like to receive it. Does that sound pushy? Provide them with an easy to use form that they can mail back at no cost or a website link to do it online. You'd be surprised at how many older folks are internet savvy.
Keep the newsletter just that, newsy. It can be fun, playful, but needs to reflect your company's brand. Provide your contact info in a easy to find place with a way for them to query you or request a visit. You could even set up an "Ask the Expert" column. If it's a virtual newsletter then it could link to a blog on your webpage.
YOU ARE NOW A BUSINESS PERSON THAT PROVIDES TREE CARE, not the other way around....