Aloysia

Aromatic shrubs, deciduous or evergreen, leaves whorled and the flowers in spikes. Typically an American sub-tropical to tropical genus, but extending as far north as California and Utah. In UK gardens normally needing a sheltered spot, or protected in winter. Well worth trying is A. citrodora (synonym L. triphylla) for the amazingly lemon-scented leaves.

The flowers produce nectar that is attractive to many midsummer butterflies, including large and small whites, small tortoiseshells and painted ladies.