Answer: Based on your description I think what you are seeing is probably normal. The flowers are interspersed along the branches. The flowers do not turn into foliage. The new growth starts as little green tufts and then elongates to eventually look more full along the entire tree. Here is a photo of a larch in bloom. You may need to cut and paste the complete url into your browser.
If you are still not sure, you might consult with the nursery staff where you purchased the tree, or with your county extension. They may appreciate an overall photo of the tree along with a few closeups of the branches and blooms.
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