Dr Mow gave you excellent advice. I too (in fact I'm doing it this morning on a couple of commercial properties on busy highways)use nice signs where the properties look really good. Like today(SUnday) I will put one of our signs on the largest account we have on a busy road. Thousands of cars pass this place per day and the turf , plants and flower displays get quite a number of complments according to the guy who manages this property. I leave the signs up from early am to early pm and then pick them up this evening.(they are closed on Sundays by the way)
I dont expect that a single call will happen short term, because we are now past the prime time for flowers, mulch etc....but....what signs will do for you is get your name out there,,,,and then when someone needs something, they may remember your business name.(we only advertise in the commercial white pages in the phone book. I've had more than a few people tell me they wrote down our phone number months ago as they were impressed with how things looked on a certain property.
If you are persistent at putting your name in front of people over and over again, you will get a response....but over time...not instantly. THese guys here on LS say it over and over and over...that word of mouth is your best advertisement. Once you start getting these referrals, they will build upon thesmselves and you may end up actually getting more calls then you can handle.....all of this assumes one thing...THAT YOU DO ABOGE AVERAGE WORK and the little extras that Dr Mow mentioned above. Too often we all talk too much about the lowballers and the cheap customers. Yes they are out there in large numbers....but I can tell you from only being in this biz full time for a couple years, that there are many people who want quality work and someone who will be reliable and professional....and they are willing to pay for it too. High quality work and good customer service is almost a lost art in our society....so when you provide this, you give people a reason to refer you, and keep you as their service provider....good luck and be persistent.