22nd February 2018
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In the garden

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All successful gardening hinges on good soil preparation. When plant­ings go wrong, it is all too often bla­med on the wind and the weather.

The elements do play their role, but in the vast majority of cases the overgrown borders and abandoned rock gardens are due to a bad start in life.

Only a minority of plants will put up with soggy or waterlogged soil, and if your plot fits that category, the drainage must be improved. There are various ways to go about this.

Sometimes the incorporation of copious amounts of bulky organic materials such as home-made com­post, shredded organic waste, farm­yard manure, preferably the kind that comes with a lot of straw, will all help to change those heavy clods to something friable. The more you use, the lighter your soil will become and the easier it will be to work it.

Organic materials also encourage earthworms, and they in turn help to lighten the soil through their tunnelling.

Where things are really bad you might have to resort to a network of open drainage ditches or, if that is not to your liking, you can lower the water table by deep ditching and the laying of land drains. The drain pipes are covered in stone chippings, before the topsoil is returned. This might seem like a lot of effort and expense, but once in place, land drains pay for themselves within two or three seasons.

The building of raised beds, for ornamental use or food production is another good way to improve drainage. Timber framing is often recommended for the latter, but even if the wood is treated, it is the least durable option. Low drystone dykes retaining soil against a building look great where space allows and is, to my mind, a better setting for alpines than the ubiquitous rockery.

Concrete paving slabs, used up­right and concreted in to give them firm anchorage, may not sound aesthetically pleasing, but are a cheap and durable solution, and soon camouflaged by a planting of trailing and hanging subjects along their edges. In a Scottish garden I visited many years ago, they had been repeatedly painted with sour milk to encourage the growth of mosses and, fully clothed in a warm rich green, looked stunning.

On well-drained and well-fed soil vegetables not only grow larger and start to crop earlier. You can space them more closely and thus fit more variety into your plot, but perhaps best of all, you can leave them to stand over winter with impunity; your root vegetables won’t rot away as they tend to do on waterlogged ground.

Much the same goes for the ornamental garden. If you want to grow candelabra primulas, marsh marigolds, water saxifrages and other moisture lovers, a stretch of bog is ideal, but apart from that, good drainage can make all the difference between success and failure.

I always remember two council house gardens, side by side, on the same soil and in the same exposure, one of them a sad place indeed, with hard-packed peaty loam and an assortment of miserable plants, while in the one across the fence there was a garden to envy. It had well-filled borders that provided colour all year round, a lawn bright with spring bulbs, and a large veget­able plot that kept the household well supplied from early summer to late winter.

There was just one difference. The productive garden had been worked thoroughly for a number of years, and every spring the gardener had dug manure and seaweed into her vegetable patch, and applied the same as thick mulch around her trees, shrubs and herbaceous plants.

Organic matter, applied as gener­ous mulch, will help matters, as the worms start to pull it down into the soil, where it starts to rot and crumble, but digging it in really speeds up things. Digging also helps to get rid of all but the most persistent weeds.

Despite all the herbicides and barrier methods such as membranes and landscaping textiles, perennial weeds remain the bane of a gar­dener’s life if they haven’t been dealt with thoroughly before any planting is even thought about, let alone started.

Grasses with a creeping rootstock will continue to creep, even if they’ve been dug under, and deep-rooted weeds, unless they’ve been removed in their entirety, will con­tinue to grow, even if it takes them several years before putting in an appearance above ground again.

In either case, weedkillers aren’t effective.

Dockens call for a sturdy fork or spade and a strong back, a task I don’t tackle myself these days, but those vile underground creepers are easily dealt with, providing knee pads and a sharp trowel are to hand.

The job has to be done thoroughly and conscientiously, with every scrap of living root finding its way into the bucket, as any fragment left behind will grow into a new plant. To make absolutely sure nothing has been left behind, rake the soil over a couple of times, with alternating pull and push motion, before level­ling and firming it for planting.

If this sounds like a lot of effort, believe me that every minute spent on hands and knees to get the ground ready will not only save a lot of time in the future, but also prevent some heartbreak. There is nothing more disappointing than a nice border that, a year or two later, has become overgrown with noxious weeds. Rockeries often come to a premature and sticky end in this way. If you start with a clean slate, you’ll get years of joy out of all your horticultural creations.

There is one more chapter to the subject of ground preparation, one that is often overlooked. Just like human beings, some plants have a sweet tooth, while others prefer it sour. Sweet in this case stands for alkaline, while sour means acid.

In my first gardening book, I believe it was called Mansfield on Alpines, I was at first puzzled by the letters NAC that accompanied most descriptions before I learned they stood for neutral, acidic and calcar­eous. Neutral means a soil pH value of 7, acid is anything below seven, and calcareous anything above. Most ornamentals fall into the NAC category, which means they tolerate a wide pH range, which is a blessing for the gardener.

Some are a little fussier. Acid lovers, also known as calcifuges, are perhaps the most particular of them all, and most gardeners know that ericaceous plants such as heathers and rhododendrons won’t grow well, or not at all, on limestone or soils with a high pH value. That also goes for Chinese gentians, and most Asiatic primulas and witch hazels.

Most plants that prefer an alkaline soil will put up with acidic conditions to a point, but will draw the line at raw peat. Snowdrops, peonies, helle­bores, viburnums, and primroses fall into this category. The latter are also a perfect marker for pH values in Shetland. Wild primroses brighten the road verges on the limestone belt that runs through Weisdale valley, but come to an abrupt end as one approaches the head of the voe, where the underlying rock is acidic. It goes without saying that our native ling (Calluna vulgaris) and creeping or sheep’s sorrel only thrive in acidic conditions.

During my consultancy work, and in the absence of nature’s more obvious pH markers, I usually advise the garden owner to have a pH test carried out by the college of agriculture, as a first step towards successful growing.

If you have individuals or group of plants in your garden that are unthrifty for no apparent reason, I’d advise you to do the same. The ideal pH value for growing the widest possible range of ornamental plants is 6.5, just on the acid side of neutral, while vegetables, especially bras­sicas, prefer a higher value.

The grass is always greener on the other side, and it is part of human nature that we all want to grow what we can’t grow. The gardeners on limy soil long for the rhododendrons that thrive on acid peat, while the gardener on peat is envious of the encrusted saxifrages that must have a good supply of lime.

Both can be helped. If your plot’s pH value is 5 or less, some liming is in order. Since the practice of liming and re-seeding hill land has fallen out of favour – and rightly so – lime in bulk seems in short supply locally. It has, as far as I can ascertain, been replaced by “Orkney sand”. This is available from agricultural suppliers, is highly alkaline, and has a coarser texture than builders’ sand, which helps to improve soil texture.

Sweetening your sour soil a little can make all the difference, but doing the opposite is not quite as easy we’re told. If you’re hell-bent on growing rhododendrons you could build peat-filled raised beds or douse your shrubs frequently with expensive iron sequestrine; both are extreme measures and quite unnec­es­­sary in most Shetland gardens.

Get yourself some granite chips from the nearest quarry, dig them into the soil and use them as a top dressing. They’ll leach acid and keep your heathers, rhodos and Chinese gentians happy for life.

Rosa Steppanova

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