Answer: There really shouldn't be any difference in growth rate of your citrus, providing growing conditions are exactly the same - exposure to sunlight, water and nutrients. It has been my experience that plants in containers suffer less transplant shock and therefore grow faster than the same plants in the ground. So, what you're experiencing is certainly puzzling. However, it sounds as both trees are responding to feeding, and to the summer weather. I'd be careful when feeding the one in the container; salts can build up and burn the roots. Use a water soluable fertilizer, diluted to half strength and apply every 3-4 weeks to your containerized citrus.
Best wishes with your trees!
Q&A Library Searching Tips