Is merging two companies a good idea when they are family owned and operated?
To better yourself, immerse yourself in learning about business. There's a high correlation between business success and business knowledge . . . and most unsuccessful owners either don't know what they don't know or fail to apply key knowledge to their operations.
That said, becoming an expert marketer could help both enterprises. If your father has been in business and survived for more than two decades, how can you use his current customer base to leverage your own landscape business? And what can he do with his current customer base to get additional business and/or customers? What would a good marketing campaign do to generate more leads? What would a 10 percent rise in his price points do for his bottom line? How would a 10 percent increase in his profit margin affect his overall profit?
Answer those questions for his business, and you will have a better idea how to answer the same questions for yours.
There are a lot of ways to get where you want to go. Just be sure you equip yourself with the best information you can. And while it may be tempting to go the merger route, it is better at this point to think in terms of niches for both companies--and work on making each successful in its own right.
All the best.