In the garden: Striking flash of purple

Purple loosestrife

Gerry Daly

July 30 2017 02:30 AM

In flower in wet ditches and damp meadows around the country, especially in the damper counties, purple loosestrife is one of the most beautiful, native wild flowers. And it is grown in gardens, too, at least in its selected forms, where it suits a damp area very well and needs little or no attention.

Its narrowly upright flower stems covered with ranks of small pink purple flowers are very striking, even from a distance. The stems can grow to one-metre tall in fertile, moist soil, or in a wet ditch, but much less in poor ground that is wet and boggy. It can be a bit over-enthusiastic in a border of less vigorous plants.

It is best planted along with other wet-ground plants, such as Japanese water iris, darmera, gunnera, meadowsweet and skunk cabbage. These are robust plants that thrive in the same conditions and they would make a fine show of colour and foliage at varied times of year.

Purple loosestrife is often seen growing by roadsides with the fluffy white flowers of wild meadowsweet. The pink cultivated forms look great with it, too. Wild valerian is another native flower that can be seen growing with purple loosestrife in wet marshy ground. Valerian has upright flower stems with rounded heads of pale-pink or white small flowers, and is not to be confused with red valerian that grows on dry stone walls, although the two are related.

Purple loosestrife flowers from summer to autumn, the flowers offering a good contrast with the many kinds of yellow daisy-flowers of late summer and early autumn. The purple looks great with the orange spikes of montbretia nearby.

There are various forms of lythrum and two species are generally grown in gardens. Some were selected from the wild species, Lythrum salicaria, such as 'Feuerkerze', with rosy red flowers; 'Robert' (bright pink) and 'Happy' (dark red). 'The Beacon' is a good variety (rich rosy-purple).

Others are selections of a different species, Lythrum virgatum, and this kind is somewhat smaller in height with smooth leaves and does not look as wild as the hairier wild species. Its flowers are smaller, too, and more red-purple than pink-purple.

A good kind is aptly called 'The Rocket'. 'Rose Queen' is a lovely variety with bright, rosy red flowers and a tidy habit of growth.

Give these plants full sunshine and reasonably good, moist, fertile soil to induce lots of branching flower stems with some height.

Remove the flower heads before the seeds are shed to prevent them from seeding about. There is a tendency to spread by sending out shoots too, but this problem is usually easily enough contained by growing them with other moisture-loving plants.