Gas plant or Dittany (
Dictamnus albus) is a wonderful garden plant that should be grown more often. The intriguing pink or white flowers are followed by unusual seed capsules that smell like lemon oil. Not surprising since this is in the same family as
Citrus, the Rue family (Rutaceae). An especially frost hardy member of the family, it grows well even in southern Scandinavia though the northern most populations are in Germany and Poland.
Of course the most fascinating trait of this plant is that its flowers produce flammable oils. Hold a match near them on a warm, still Summer evening and the oil will ignite and flare up. Though in my garden they mostly bloom in late Spring.
There are several videos online demonstrating this effect.