The quoted text makes it sound as if that particular time of year wasn't when such flowers would normally bloom. Florists, of course, have cut flowers available all year, but perhaps these blooms were actually potted, growing plants in a place/time they wouldn't normally be seen (roses growing in December in Alaska, for an extreme example)? And that's why they were unseasonable....? Even with more context, I think that this sentence would be considered to contain awkward phraseology.
Student or Learner