Why native wetland plants earn their place

Britain's fens, marshes, pond margins and damp meadows were once stitched through the landscape, and the plants that grew there evolved alongside our bees, hoverflies, butterflies and moths. That shared history matters. Native wetland species flower when our pollinators need them most, offer nectar and pollen in shapes and depths our insects can actually reach, and ask for little more than damp ground and a decent stretch of sunshine.

You do not need a pond to grow them. A bog garden, a damp border, a half-barrel on a patio or a few large pots standing in saucers of water will all do the job. Here are three of the best natives to start with, plus a supporting cast worth knowing.

Purple loosestrife: the tall magenta magnet

Purple loosestrife (Lythrum salicaria) sends up stiff, elegant spikes of magenta flowers from June right through to September. It is one of the finest late-summer nectar sources we have, and its flowers are deep enough to reward the long-tongued bumblebees — garden, red-tailed and carder among them — that often struggle with shallow, open blooms. Hoverflies crowd the spikes on warm afternoons, and butterflies will visit when little else is in flower.

Grow it in full sun at the edge of a pond or in any soil that stays reliably moist. Plants reach roughly 1.2 metres, so give them room and plant in groups of three to five for impact. Leave the seedheads standing through winter — they feed finches and shelter overwintering insects — and cut back hard in late February or early March.

Water mint: small flowers, huge footfall

Water mint (Mentha aquatica) is the quiet workhorse of the wetland garden. Its lilac, pom-pom flowerheads appear from July to September and are shallow enough for short-tongued bees, hoverflies, bee flies, small beetles and a steady stream of butterflies, including peacock, small tortoiseshell and comma. The aromatic leaves are also a larval food plant for the mint moth, whose tiny caterpillars stitch the foliage together.

It thrives in shallow water at the pond edge, in boggy ground or in a pot plunged into a tray of water. Be warned: it spreads by runners with real enthusiasm, so plant it in a basket or a large pot if you want to keep it in bounds. Cutting it back lightly in midsummer encourages a fresh flush of flowers into autumn.

Hemp agrimony: the butterfly buffet of late summer

If you plant only one thing for butterflies, make it hemp agrimony (Eupatorium cannabinum). Its fluffy, dusky-pink heads open from July to September and are irresistible — red admiral, peacock, small tortoiseshell, painted lady and comma will all settle on them, often several at once. Bees, hoverflies and day-flying moths join the party, and a handful of specialist moths use it as a larval food plant.

It grows to around 1.5 metres on stiff, reddish stems and is more forgiving of drier soil than the other two once established, though it still prefers a damp root run. Plant it towards the back of a border or in the moist margin of a wilder patch, and resist the urge to tidy it away in autumn.

A supporting cast of British natives

Once you have the trio above, widen the season with a few companions.

• Marsh marigold (Caltha palustris) — golden cups in April and May, invaluable for early-emerging queen bumblebees and hoverflies.
• Water forget-me-not (Myosotis scorpioides) — delicate blue flowers from May to July, loved by small bees and hoverflies.
• Ragged robin (Silene flos-cuculi) — pink, frayed petals that draw in bumblebees and butterflies.
• Greater bird's-foot trefoil (Lotus pedunculatus) — a nectar source for bumblebees and the food plant of the common blue butterfly.
• Water figwort (Scrophularia auriculata) — modest brownish flowers that wasps, bees and hoverflies adore.
• Meadowsweet (Filipendula ulmaria) — creamy heads in summer, popular with hoverflies, beetles and small bees.

Planting, siting and the quiet rewards

Choose a spot in full sun — six hours or more — and use a peat-free, loam-based compost. In a pond, plant in aquatic baskets lined with hessian to stop the compost escaping. In a bog garden or damp border, work in plenty of organic matter and water well through the first summer while roots establish.

For small spaces, a 30–40 litre pot standing in five centimetres of water suits water mint and marsh marigold beautifully, and purple loosestrife will cope in the same arrangement if kept well watered. Refresh the water regularly to stop it stagnating, and never let pots dry out completely.

Avoid fertiliser, which encourages lush leaves at the expense of flowers, and avoid pesticides entirely. Plant in generous groups rather than single specimens, and leave stems and seedheads standing until late winter.

Then simply watch. There is a particular pleasure in sitting by damp ground in August — the air thick with hoverflies, a red admiral opening and closing on the hemp agrimony, bees working down a loosestrife spike — and knowing that this small, wet corner is doing real work for British wildlife.