The Herald - The Herald Magazine
Plants for wet soil There’s no shortage of options for the all-too-common condition
MOST garden plants need moist, free-draining soil, but what do you do – and forgive me if this sounds painfully familiar – if the moisture doesn’t drain freely and the ground is cold and wet? The garden may be on a slope, so water collects at the bottom where clay subsoil impedes drainage. Spells of heavy winter rain simply make matters worse.
It may be obvious that a patch is waterlogged and so has to be treated as a bog. Confirm this by digging a hole two spades deep, cover it so that rainwater can’t get in and leave it for 24 hours. If the hole starts filling with water, you’ve got a bog garden which you’ll have to live with. Buy bog plants or make a pond feature.
If the hole stays dry, fill it with water and see what happens. If the water’s there the next day, you’ve got poor drainage. Plant roots rarely go deeper than 45cm, so check the sides of the hole to that depth. If the soil is too dense and hard for roots to penetrate, dig the ground over to loosen it up. But if there’s an impenetrable level of clay or stone at the bottom, hand digging will never break it up. In that case, choose plants that tolerate wet but not waterlogged conditions.
Shade often prevents the sun from drying out the soil after winter rains, and shadiness can creep up on you unexpectedly. A part of my garden was once great for sunbathing but was next to the road, so we planted a mixed hedge for privacy. After a few years, the deckchairs were moved and the lawn turned mossy.
Admittedly this was self-inflicted and we could have cut down the hedge, but you probably don’t want to fell a favourite flowering cherry or deny yourself an apple tree’s harvest. Nor can you do anything about a neighbour’s tree or a high boundary wall or a hedge. One way or another, you’re often stuck with cold, wet soil.
You might decide on an expensive garden make-over, felling trees and ripping everything up to install a state-of-the-art drainage system. Or you could go with the flow and choose suitable plants.
There’s no shortage of annual, biennial and perennial flowers, and even shrubs and trees that cope with all-year-round damp or even wet soil. These include Hydrangea macrophylla, Leycesteria formosa, astilbes and some irises. And you’ll quickly see if you’ve chosen the right plants: they’ll thrive or die in no time at all. If you live in a suburban area, your neighbours probably have the same problem, so check out which plants work for them.
Most survivors of wet conditions are all too keen to spread and dominate an area, so know what you’re planting and keep on top of any potential thugs. They’ll take full advantage of soggy ground and achieve the height and spread you’d expect after four years in half that time. And this speedy growth is often lush and brittle, so needs more staking than you’d normally expect.
Ornamental rhubarb, Rheum palmatum, is an attractive choice for these conditions, readily forming fine big clumps with 3m-tall flowering spikes in a couple of years. Many ferns also love permanent moisture. The deciduous ostrich fern, Matteuccia struthiopteris, tolerates a north-facing wall and lets you enjoy bright, young, springgreen shuttlecock fronds. And if you’re after good ground cover, look to Blechnum chilense and its dark, evergreen fronds.
Be warned: these guys will quickly shade out any competitors. And, however appealing Lysichiton americanus, skunk cabbage, may be, it’s so invasive that, under EU regulations, it’s an offence to release it into the environment.