Have you worked with Japanese Black Pine before?
I killed one once. It was a baby.
Well, you can inquire with the person from whom you bought it to be absoluetly sure, but it's definitely a JBP in my book. I'm glad to see you winter it in the greenhouse - they're not very cold-hardy.
And there's no time like the present to start learning. First thing to learn is that there's a season for everything. It's too early to decandle, but you can "pinch" candles. When you pinch them, you just break them off above where the needles are beginning to emerge. Remember that with black pines, everything we do is with an intention to balance the growth. By "balance", I mean that all of the candles are growing at the same time and are the same length. All of the needles are the same length and density everywhere on the tree. So everything we do is with the deliberate intention to weaken the strong and strengthen the weak. So with candle pinching, you break the big candle only. Leave the little ones alone.
To learn the mechanics - go to Jonas' page and read carefully this post:
http://bonsaitonight.com/2015/03/31/pinching-spring-candles-on-black-pine/
I think you can carry it out on your tree.
Only candle pinching for now. Nothing else. It's not the season for it. You can use the quiet time to learn more. Read the other entry's in Jonas' blog to learn the rest of the seasonal techniques for black pine care. You'll love them - they are really fun to grow.