When are grasses not grasses? When they’re rushes or sedges. The latter are an attractive alternative to grasses and thrive where grasses couldn’t: woody, shady, wet and soggy spots, even pond margins. They’re the perfect answer for these problem areas and aren’t used as much as they should be.

Confusingly, some nurseries and garden centres that should know better label sedges as grasses. So, if you fancy the thought of sedges, you’ll need a clear idea of how they differ from grasses.

A fine old ditty should help. “Rushes are round and sedges have edges, but grasses, like a***s, have holes.” This describes the cross-section of stems. Rushes have solid stems usually filled with pith. Sedge stems are triangular in section, but grass stems are hollow pipes.

The stems of sedges are always solid, with three leaves coming up from the lower part of the stems. This gives them a triangular appearance. They can be more striking than many grasses, and the larger species, such as Carex pseudocyperus, make a stunning addition to any display. This hop sedge boasts a mass of fine flowers drooping from 1m-tall green stems that turn golden brown in autumn.

Another clue for horticultural sleuths is the Latin name. Most sedges are in the genus Carex, the largest member of the Cyperaceae family. Other genera are Trichophorum, which includes deergrass; Eleocharis with the spike rushes; and Eriophorum including the cottongrasses. The common names don’t help: common cottongrass with its fluffy, white cotton-wool seed heads is no grass but rather Eriophorum angustifolium.

There’s a goodly choice of sedges for shady bogs and ponds. Carex pseudocyperus is a fine specimen plant, its golden-brown flowers drooping elegantly from yellowy-green stems. And C paniculata, aptly known as tussock sedge, forms dense clumps beside a pond. Its mass of feathery flowers turns black when the seeds ripen.

Although most of the readily available sedges are pond marginals, some will also cope with damp, wet areas that aren’t quite bogs or ponds. In part of my garden, we’ve let some fine hardwoods, including an elm, grow away and cast their shade. But we’re also cursed by living next to one of the sitka spruce plantations that darken and smother so many of Border hills.

I’ll park my dislike of variegated plant leaves and consider some low-growing Carex siderostichas. Shima-nishiki’s golden variegation is better than the white paint splashes of variegata.

As a genus with more than 1,500 species, it’s no surprise that some sedges need dry, sunny places as well. As an evergreen, Carex divulsa is utterly invaluable, forming a mound of striking dark-green leaves. At 35-45cm, it sits comfortably at the edge of a dryish border.

Carex aurea, golden sedge, is another possibility. What strikes me about this tough little dwarf are its bunches of round green seeds springing up from a mound of golden foliage. The seeds are gradually infused with orange.

Although some more unusual sedges are available as plants, you may need to grow other varieties from seed. Carex gravi, mace sedge, grows to 45-60cm, sprouting distinctive star-like seed heads. It’s an ideal plant if you like cut flowers.

Even if you live by the sea, sedges will come to the rescue. Carex flacca, glaucus sedge, with brown-purple flowers in late summer, takes salt spray in its stride. Provided it’s in a sunny place with alkaline soil, it’ll handle damp or dry ground.

But, when choosing sedges, think twice when you see them described as "vigorous" and "spreader". Carex riparia, greater pond sedge, is a headache in waiting. And Arundo donax is probably worse. We planted one in the pond at our demonstration garden, only to find it forcing its way through the liner in no time at all in its ruthless quest for mastery.

Visit wildflowershop.co.uk, wetland-plants.co.uk and plant-world-seeds.com