“Laburnum” is a genus for two small trees in the pea family.  The flowers are bright yellow on long hanging stalks with many flowers together.  Both species are sometimes called “golden chain tree”.  Gandalf’s fireworks, to be described that way, must have been long, swooping successions of gold starbursts.

• 01.017 and laburnums of fire

Wikipedia contributors. “Laburnum.” Wikipedia, The Free Encyclopedia. Wikipedia, The Free Encyclopedia, 21 Apr. 2015. Web. 9 May. 2015.