Fertilize at the beginning of the first spring season after planting the tree. Adding fertilizer right away may stunt the growth of a Thuja Green Giant.
Use a 10-10-10 fertilizer every two weeks starting after the last frost of the season and until the first week of summer. Use of a stronger fertilizer during the first year of the tree's life could kill the roots.
Decrease the amount of fertilizer to once per month during the summer. Continue fertilizing the tree until the ground begins to frost over.
Stop fertilizing your Thuja Green Giant during the winter.
Fertilize the tree in the same time increments for as long as you have the tree. You can begin using a stronger fertilizer on the second year.