A wetland garden has benefits: with appropriate planting and a little care, you can enjoy lush, wild growth
THIS SUMMER'S abundant rain is washing the lustre off my spirit, no doubt about that. But the bright side of this damp situation is that there is a sort of lushness about my garden that I've never experienced before - or rather, only once before and that was last summer.
Our ground is dry, terribly dry, but the past two years have given me a temporary taste of what it might be like to have moisture-retentive soil. It has also given me pause, yet again, to envy those of you who are blessed with damp gardens.
"And cursed, too," I can hear you thinking. For the soil that retains moisture must be managed far more carefully than dry soil. With the latter, it's mainly a case of regularly laying mulches of organic matter (compost, well-rotted manure or other decomposables) and letting the worms dig it in. Moisture-retaining soil, however, can go horribly wrong if it is trampled upon, dug into or planted when wet, or otherwise inadvertently offended.
In the gardens of readers of this column, heavy clay is probably the most prevalent kind of damp soil. It occurs in many counties, including north Dublin, Kildare, Meath, Westmeath, Longford, Cavan, Roscommon, Leitrim, Sligo, Clare, Limerick and Wexford. And if you get in a few tonnes of topsoil to fill new beds, it's possible that it too will be heavy clay - especially if you live in the Dublin area.
Now I'm not usually an advocate of digging, as it can destroy the soil structure. If soil is reasonably healthy, the worms will normally do all the digging and mixing that is necessary. However, although the earthworm can move prodigious amounts of soil and is an expert driller of aerating tunnels, I haven't met one yet that can lay land drains or can swiftly incorporate large quantities of gravel into waterlogged soil. So, if your soil is heavy, poorly drained and tends to stick together, then it may be time for a once-off, mammoth digging session.
Where there is lots of water which may be flowing down from higher ground or rising from nearby springs, you'll probably need to put in land drains or get someone else to do it. There's no room to describe how it's done here, but there is plenty of information in books and on the internet. And, of course, any Irish farmer can hold forth at length on drains.
Alternatively, you could manage a really saturated area of your garden as a wetland - especially if you have a large property. Native plants will give it a pleasingly wild look and attract lots of creatures. Consider bulrush (Typha latifolia) and T. angustifolia, reed grass (Phragmites australis), burreed (Sparganium erectum), yellow flag (Iris pseudacorus) and meadowsweet (Filipendula ulmaria).
Trees such as alder, willow and birch will form a canopy and will be welcoming to birds. Such a planting scheme can more or less look after itself - although you may want to coppice the trees every few years to keep the area open.
But, if you wish to grow a larger palette of moisture-loving plants, then a bit of soil amendment can make a a world of difference. Clay soil consists of tiny particles that stick together when wet. If you handle, dig or work the soil when it is in this condition, the particles bond to form an impenetrable material (pottery, remember, is made from clay). Gravel and organic material (garden compost or well-rotted manure) help to aid drainage and to open up the structure, and can be dug in when the soil is not too wet.
Autumn is usually the best time for this operation as the soil has been active and warm during the summer, and there is less danger of damaging its structure.
When digging clay soil (or any soil, for that matter), don't mix up the subsoil with the topsoil. Subsoil is easily distinguished because it is a different colour and consistency. If the subsoil makes a hard and water-impermeable layer, try to break it up a bit with a crow bar or mattock.
With a more open, but still moisture-retaining soil, dainty pretties such as spotted orchid (Dactylorhiza) and primulas (many kinds, including P. beesiana, P. bulleyana, P. denticulata, P. florindae, P. japonica, and P. pulverulenta) will grow for you. So also will ferns, hostas, astilbes, a rake of different irises and hundreds of other plants.
Plants that thrive in this kind of habitat are often dramatic, with larger, more luxuriant foliage, and bigger, brighter flowers. Some are so exaggerated in all their parts that they are like cartoon plants.
For instance, skunk cabbage (Lysichiton americanus) has canary-yellow, cowl-like flowers and vast green paddles for leaves. The umbrella plant (Darmera peltata) puts up improbable pink drumsticks composed of dozens of tiny flowers in spring and follows these with elegant green parasols. Then the so-called giant rhubarb (Gunnera manicata), no relation to its culinary namesake, is everyone's favourite crazy plant, with its two to three metres, heavily-ribbed, prickly tents of leaves.
One final word on damp soil: the surface of clay is prone to "capping" by rain, especially in heavy weather. This happens when the fine particles are mashed together by the pressure of the water drops, and they form a hard layer that sloughs off further moisture, rather than absorbing it. Mulching the surface with straw, garden compost, or fine wood mulch will prevent capping.
PLANTS FOR DAMP GARDENS
Trees and shrubs
Alder (Alnus, all), birch (Betula, most), katsura (Cercidiphyllum japonicum), dogwood (Cornus, most), Hydrangea paniculata, poplar (Populus, all), blackthorn (Prunus spinosa), willow (Salix, all species, but keep away from buildings as the roots of larger trees may damage structures), elder (Sambucus, all), rowan (Sorbus aucuparia and its cultivars)
Perennial plants with luxuriant foliage
Darmera peltata, Gunnera manicata, hosta, yellow flag (Iris pseudacorus), ligularia, skunk cabbage (Lysichiton americanus and L. camtschatcensis), shuttlecock fern (Matteuccia struthiopteris), royal fern (Osmunda regalis), Rheum species, rodgersia, arum lily (Zantedeschia aethiopica).
Other perennial plants
Astilbe, marsh marigold (Caltha palustris), lady's smock (Cardamine pratensis), Dactylorhiza, meadowsweet (Filipendula ulmaria), Iris ensata (and its many cultivars), Lobelia cardinalis (and its cultivars), yellow loosestrife (Lysimachia punctata), purple loosestrife (Lythrum salicaria), monkey flower (Mimulus), primulas, globeflower (Trollius), Ranunculus.
Diary Date:Today (August 9th) 2-5pm, South County Dublin Horticultural Society annual summer flower show at Dún Laoghaire-Rathdown County Hall, Marine Road, Dún Laoghaire. Admission €3.