Plant Lythrum in reliably moist soil in full sun, where it will produce tall, colourful flower spikes through summer. It also grows well in a pond basket positioned at the water’s edge, with the crown just above the waterline

Apply a generous mulch of well-rotted compost around the base in early spring to feed the soil and plant, and help retain moisture. Deadhead or remove fading flower spikes if you want to limit self-seeding and keep growth tidy.

Cut back spent stems to ground level in late autumn to prepare for fresh growth the following spring.