If you got the tree fully in-leaf and planted it, then it is possible you will see no more growth. Some japanese maples are done with their spring flush of growth pretty early in the season. By late spring to early summer and into fall, the tree should produce good root growth, with or without any more top growth.

Some varieties or cultivars of Japanese maples will put out a second flush of growth in mid to late summer but not all. Depending on the shock to the tree due to planting you may or may not see this. Fertilizer applied in early summer can also cause this later season growht, but I do not recommend nitrogen fertilizers for at least a year. If you want to use a little liquid 0-10-10 mixed at 1/2 strength and apply monthly for the season that would be fine.

It can take 2-4 years on the ground for you to see "typical" growth characteristics as well as leaf shape and color. For example, a 3 year old Bloodgood planted in the ground here in Southern, Oregon, after being grown in nursery shade, can take 3-4 years in the ground with adequate sun to develop the correct leaf shape and deep purple color.

Michael