Purple Loosestrife can be the mainstay of summer planting as it offers height and colour towards the end of the summer season when you are craving something new. Lythrum salicaria ?Robin' can be very long-flowering and with those towering spikes of beautiful pinky-purple flowers, it will provide interest when other plants are starting to fade. It's the perfect plant for gardening beginners because all they require is a position in a moist, sunny border and they will delight year after year. Height: 90cm (36). Spread: 45cm (18).