let me see, one tree per every 15 seconds. That's four per minute, 240 per hour. Given an eight hour day, that's 2,520 per day. Five day work week makes it 12,600 per week and 50 weeks of work a year (need a vacation you know)....WOW! This guy was busy for almost two SOLID years.
When did he have time to study physics?
Let's look at the numbers, say he plants a million trees at the rate of one tree per day;
1,000,000 trees @ 1/day divided by 365 days per year = 2739.726 years (without factoring the unknown amount of over 1,000,000 trees).
Lets say he has plants a million trees @ 100/day = 10,000 days divided by 365 days per year = 27.39726 years.
Now that's more like it ! < /humor >