Q.Spindly Pinkerton Avocado Tree
I just got it in March and it has grown 2 feet already. It is in a pot. How can I make the trunk stronger?

Certified GKH Gardening Expert
It sounds like the tree doesn't get full sun. Anything less than 8 hours of direct sunlight, or equivalent, will cause a spindly tree. Otherwise, test the soil for nutrient deficiencies, though these will appear as lesions or spots on the leaves rather than stem elongation.
Here is an article for more information on the care of the tree:
https://www.gardeningknowhow.com/edible/fruits/avocado/indoor-avocado-plant-care.htm
This collection of articles will offer more information: