Splish, splash, splosh. Recent statistics from Met Éireann paint a very wet picture of the kind of weather Irish gardeners – and their gardens – have had to endure in recent months, including wild winter storms, gale force winds and well-above-average rainfall. Cork, with a whopping monthly total of 211.4mm of rain, had its wettest December since 1989. January 2014? Not much better, with parts of the country recording monthly rainfall amounts roughly 50 per cent above average.
The result is that most Irish gardens are sodden, their plants storm-battered, their lawns waterlogged, their soils unworkable. In even poorer shape are those that lay temporarily underwater as a result of flash floods. Here, the sheer mass and weight of swirling floodwater (in worst cases, contaminated by effluent) caused soil compaction and erosion, exposing vulnerable root systems and robbing the soil of oxygen, nutrients, and, as the water retreated, even its surface layer of particles.
Why does this matter? Well, it matters because healthy, living, resilient soil is the heart and soul of any garden. And you can’t have healthy, living, resilient soil without a healthy soil food web; a complex, delicate ecosystem made up of air, water, minerals and many different micro and macro-organisms. It transforms organic matter into humus, protects soil structure, retains and provides plant nutrients, and protects against plant diseases and pests. But in a flooded and/or compacted soil, it’s knocked completely out of equilibrium, while in a saturated soil, its processes slow to a halt.
So what can we, as gardeners, do to help?
Firstly, stop digging. Not only is it unnecessary but it’s also damaging to soil structure, leaving it ever more vulnerable to the degrading effects of heavy rainfall and flash flooding. Instead, only shallowly cultivate the uppermost layer of the soil, using a hoe/hand tools and mulches to suppress weed growth.
Secondly, never walk on or attempt to work wet soil, which will only damage it. Don’t let the promise of one sunny day tempt you to take up tools and start licking the garden into shape, but give it a proper chance to dry out. Even then, avoid walking on the soil; laying a wooden plank on the ground as a crude walkway will disperse the weight of heavy footsteps.
Thirdly, don’t leave soils nakedly exposed to heavy winter rain. With vegetable beds, give them a mid-autumn mulch of garden compost, (adding manure to compost heaps is a great way of mixing the two materials as well as speeding up the composting process), then either cover with plastic sheeting or, even better, sow a green manure as a cover crop on top of it, for cutting back and incorporating into the soil the following spring.
A green manure is a living crop that helps improve soil fertility and structure. Above ground, its leafy canopy helps protect the soil surface from erosion, and suppresses weeds. Below ground, its root systems help aerate the soil, prevent leaching of nutrients and improve drainage. Depending on the plant, it can also fix or hold nitrogen in the soil, while some are especially good at remedying the problem of soil compaction. The slowest-growing, deepest-rooted kinds are grown over a two- to four-year period and bring the richest, most long-lasting benefits. The fastest-growing, such as mustard, (Sinapsis alba) can be sown in autumn or spring, and dug back into the soil just four to six weeks later. They won’t do as much as slower-growing types but they’ll still greatly enhance soil health by adding nutrients and organic matter.
In the case of flower-beds, green manures clearly aren’t suitable. But you can still do a lot for the soil ecosystem by adding a thin layer of humus-rich homemade garden compost. Wait until mid-spring, when soils start to dry out and warm up, before spreading it. Where the ground looks badly compacted or ‘capped’ (this happens when heavy rain causes surface soil particles to bind together in an impermeable layer), then spike the soil with a garden fork to aerate it.
Manures and garden compost aside, there are other practical ways to protect gardens from flooding. Use fewer hard, impermeable materials. Build raised beds. Plant shelterbelts of trees and shrubs, whose root systems will drink water and help soil structure. Finally, check rainwater systems are clear of debris and properly functioning. The added bonus is that there's nothing like the messy task of cleaning out clogged gutters to make one feel terribly virtuous.
See cotswoldsseeds.com for a complete guide to green manures
Diary Dates
Wednesday, February 12th
Kill O' The Grange Parish Centre, Kill Lane, Co Dublin. "New Friends and Old Favourites", a talk by Gerry Harford for South Dublin Horticultural Society. Visitors, €5.
IN THE GARDEN THIS WEEK
Where soils are passable, prune apple trees and soft fruit bushes.
