Common St John’s Wort Seeds Hypericum Perforatum – is a good general-purpose meadow plant that grows well on a wide range of free draining soil types where there is plenty of sunlight. Plants typically grows to about 2 foot in height and produce bright yellow flowers from June to September. Common St John’s Wort is a useful plants for bees and looks best growing with other wildflowers that bloom in mid to mid late summer such as Common Agrimony, Greater Knapweed, White campion and Small Scabious. Alternative Names for Common St John’s Wort include Perforate St John’s Wort