Ask about the company's advanced training designations, i.e. "Do you your employees hold any special designations, like a FNGLA certification or Arborist designation?" and, if so, "what degree of excellence have they achieved?" Knowing how serious the company is about training and about hiring only the best will go a long way towards helping you make a choice
Knowledge, Skill, Experience
The proof of a great landscaping company can be measured by these indicators, all under the heading of "how many years have you been in business? How large is your staff and what is the average tenure of your key employees? and "How many different services (disciplines) are you expert in?"
This is the most important of all first impressions. Workers not wearing uniforms whose appearance is unkempt and whose clothes are dirty, even though they are in a "dirty" business, will tell you a lot about the professionalism and attitude of a landscaping company.