I have purchased a Larix laricina ‘Blue Sparkler.’ It appears to be a dwarf larch but I can’t find any information about it. Could you point me toward a reference?
According to an article by Kathryn Lund Johnson in The American Gardener, volume 87, no. 6. (2008) entitled “Wicked and wonderful: witches’ brooms,” Larix laricina ‘Blue Sparkler’ is a witches’ broom cultivar. It was introduced in 1993, and is a dwarf deciduous larch with “a dense habit that is reminiscent of miniature fireworks. Its blue green needles turn gold in autumn, then drop. In 10 years, it can grow three feet high and two-and-a-half feet wide.”
Witches’ brooms are a type of deformity that can occur for a number of reasons, according to the article, including dwarf mistletoes, fungi, viruses, bacteria, and aphids. Witches’ brooms on conifers are used as a source for propagating new cultivars. The propagator takes a cutting from the broom, and this ‘scion’ is “either rooted directly or grafted to young conifers that serve as the ‘understock.’ When grafting, the wound is given a year to heal. The understock is then removed and a new plant stands in its place.” This method was pioneered by Sidney Waxman, a professor of plant science at University of Connecticut, Storrs. He is responsible for developing the ‘Blue Sparkler’ tamarack you are growing.
Iowa State University has a page of information about the phenomenon of witches’ brooms.