Mock Vervain (Glandularia, Verbena × hybrida, V. peruviana), fam. Verbenaceae.
This ornamental plant, originating from America, is very rare in Kyiv. It is propagated from seeds and grafts. If planted indoors in pots in advance, the flowers will appear as early as May. Scarlet and lilac flowers of the cultivars are very abundant for that small plant size (less than 20 cm).
Despite so similar names in Russian and Ukrainian, Vervain does not have anything in common with Willow or Loosestrife.