Our collection of sorts is three years old now, the trees are healthy, grow beautifully and can be visited after pre-scheduling! We have 10 pieces, about 15-year-old huge pecan trees as well, but these are also the seedlings of the late-ripening varieties and their nuts rarely ripen. Pecan trees (carya illinoinensis) take 20 to 25 years to reach full maturity and get 60-100 feet tall, with a spread of 30-50 feet across. But don't get discouraged yet: Pecan trees started from container grown stock (such as the ones Perfect Plants offers) will begin to produce nuts in as little as 4-8 years..