I have 2 established Emperor I that are looking scarce like this right now, but I noticed that there are still a lot of unopened buds, as CPPgardener said, it is still early (17th May now) and at least where I'm (Montreal Quebec) it has been a rather cold Spring so far. Low day temps do not promote fast growth. Even if you don't see big obvious buds JMs can throw new growth from secondary buds, you can't easily see. Best of luck with your tree and do post updates so we all can learn from your experience