Each and every person born on earth will (have to) belong to any one of these 27 stars. If you have the exact time of birth, it can easily be traced down by any astologer. Now each tree here corresponds to that particular star.
Each tree here keeps giving energy to that particular person / people born during that particular star. So any ailments or health problems are set right / healed / cured when you spend / request / talk / meditate near or under that particular tree, corresponding to their star.
So the presence of the complete set of 27 trees directly creates a healthy and sound physical, mental, psychological and spiritual beings. Which is the ultimate and absolute bliss to oneself and to the earth too.