Why a reedbed edge is worth the space

If your pond is more than a couple of metres across, the shallow shelf around its rim is the most biologically productive square footage you own. A reedbed edge makes use of that shelf properly: common reed and reedmace push stems up through the water, draw nutrients from the silt, and turn an ordinary garden pond into something that reads as a proper bit of fenland.

The practical benefits come first. Dense stems slow the water at the margin, so suspended particles settle out and roots and rhizomes take up nitrate and phosphate before algae can use them. The same stems give fish fry somewhere to hide from hungry adults, and frogs, newts and dragonfly larvae a place to lurk. Then there are the reed warblers, which will not nest in anything less than a decent stand of tall vertical stems.

Choosing your reeds

Common reed (Phragmites australis) is the backbone of any reedbed. It runs, so it spreads by rhizome given half a chance.

• Common reed — tall, feathery seed heads by late summer, superb for reed warblers and for the rustling sound alone. Plant it knowing it will travel.
• Lesser reedmace (Typha angustifolia) — slimmer and better behaved than the familiar bulrush, with narrower leaves and smaller seed heads.
• Bur-reed (Sparganium erectum) — smaller, well-mannered, with spiky seed heads that finches and tits will work over in autumn.
• Reed sweet-grass (Glyceria maxima) — good for filtration and cover, though it can be thuggish, so treat it as a filler only if you have room.

Common reedmace (Typha latifolia) is the one most widely sold, and it is magnificent, but in a pond under about 20 square metres it will take over. If you want it, keep it in a large sunken container.

Preparing and planting the shallow shelf

Reeds want still, shallow water — between about 5cm and 30cm deep over a base of silt or heavy loam. If your pond has steep sides, build a shelf with a rolled length of butyl or a timber batten, or simply plant in baskets stood on existing ledges.

Use a heavy, peat-free loam or aquatic planting compost — never ordinary multipurpose, which floats and feeds algae. Plant bare-rooted divisions in spring, from March to May, when the water is warming and the rhizomes are starting to move. Space them 30-45cm apart; they will close the gap within two seasons.

Top each basket with 2-3cm of washed gravel to stop koi and tench rooting them out, and to hold the compost down. Set the baskets so the crown sits just below the surface. If your pond is stocked with carp, plant in the shallowest water you can get away with, or protect the new growth with a temporary mesh ring for the first summer.

Keeping it in bounds

Reedbeds in small ponds need an honest management habit. Sink a rigid liner or a root barrier to at least 45cm around the planting area if you cannot give the reeds a whole bay to themselves. Lift and divide container-grown clumps every third year, cutting back the rhizome with a spade and replanting the vigorous outer pieces.

Cut stems in late winter or early spring, before the new shoots show — never in autumn, because the standing hollow stems are where over-wintering invertebrates shelter. Leave a third of the stand uncut each year so there is always some older growth, and stack the cut stems beside the pond for a week or two so anything living in them can crawl back to the water.

What turns up

A mature reedbed edge is rarely quiet. Reed warblers arrive from mid-April, chattering from deep in the stems — you will often hear one long before you see it. Sedge warblers and reed buntings follow, and swallows and house martins will hawk insects above the heads.

Dragonflies are the other great reward. Emperors and four-spotted chasers use the tall stems as emergence perches, and the larvae hunt among the roots. Look for blue-tailed and azure damselflies in the shallows, and for the characteristic exuviae — the empty larval skins — left clinging to stems a foot above the water in June.

Underneath, the slower water at the margin becomes a nursery: tadpoles, stickleback fry, water boatmen, and the occasional grass snake hunting them.

A simple yearly rhythm

Spring: divide and replant anything outgrowing its space, check barriers. Summer: watch and enjoy, and top up the pond with rainwater rather than tap. Autumn: leave the seed heads standing for the birds. Late winter: cut a proportion of the stems back to about 15cm above the water line, clear any dead material from the open water, and let the reeds start again.