Ages ago I got some seeds of Syringa meyeri, the Meyer or Korean lilac, and they grew in a wooden box for years. Then we moved here in 2006 and they remained in the box, never getting more than about a foot tall. I finally planted them in the garden and for a few years they grew larger but didn’t bloom. Last year they bloomed and this year they are larger and blooming better still. They have large leaves and the flowers are at the top in fairly large terminal clusters (panicles).