Mud Sweat and Soil
Good soil in the basis of any garden but some soils can be more forgiving than others says Nigel Colborn. But do not despair even in the hardest conditions nature has a few surprises
When I was little I was taken to task by my grandfather for asking him why he was digging in the dirt. “This is not ‘dirt’,” he told me, cupping his hands and scooping up part of his vegetable bed, “it’s soil”.
And as he warmed to his theme, he allowed the friable, Spalding silt to run through his fingers. “It’s alive,” he went on, “full of animals so tiny you can’t see them. Plants can’t live without soil, and we can’t live without plants – so never insult it by calling it dirt.” Grandpa’s words taught me the first lesson that every gardener has to learn: respect for the soil. Later, that respect becomes understanding and, if you get truly hooked on horticulture, understanding turns to love.
Soils vary, of course and very few are ideal. Some, like the fenland silts of East Anglia, or the fertile ‘brick earth’ in the West Midlands, are so rich and easy to work that they’ll grow almost anything, with minimal effort. Others, such as the heavy, sticky clay of Northamptonshire, or boulder-strewn limestone of the Cotswolds are much more challenging and demand more careful management. But no soil, not even the very worst, is so bad as to rule out gardening. Wild flora have even been known to colonise toxic wasteland where the ground is so alkaline that it is practically corrosive.
The secret, if you want to succeed with your garden, is to familiarise yourself with its soil. Check whether it is acid or alkaline, find out how quickly it drains and check whether it has been well-managed in the past. Know what you are up against, and the rest becomes much easier. Not only can you take a whole variety of actions, to reduce the disadvantages, and play on the advantages, but you will also have a clear idea of which plants will thrive, which will need extra help and which are not even worth trying.
To help you out, here are some fairly typical soils, with suggestions on how to get the very best out of them.
Clay soils are amongst the most difficult to deal with, but are often the most fertile. They hold nutrients that could otherwise wash through in the rain, and they are pretty good at retaining precious moisture. Take great care never to walk on clay soils unless they are dry. Even then, keep off them as much as you can. When you dig, consider laying a plank down, and walking on that, rather than on the bare soil, since it reduces pressure and, therefore, prevents compaction. Compacted soil contains no air, is easily waterlogged and is impossible for roots to penetrate.
Adding coarse or woody material, especially if it has been through a shredder, will help to open up the structure and will improve drainage. If cracks appear, in summer, take advantage of this by pouring sand or coarse grit down them. Then, when the clay becomes damp again, and expands, the sandy seams will assist drainage.
The choice of plants, for clay, is vast. Roses love it and, once established, will grow well and flower for long periods. Such spring shrubs as forsythias, Philadelphus, Deutzia and lilacs also thrive in clay. Most evergreens, particularly hollies, euonymus, laurels and box also cope well with clay.
Herbaceous plants which enjoy moist conditions will usually settle well in clay. Astilbes, Ligularia, Siberian iris, the taller grasses such as Panicum, Miscanthus, Chasmanthium and Carex pendula all cope well too. And for early summer, in a damp border, consider planting displays of Candelabra primulas, perhaps followed by bold leaved, elegant Rodgersias.
CHALK UP YOUR SUCCESSES.
Chalky or limy soil often combines a double problem — dryness and extreme alkalinity. The former stunts growth, but the latter causes serious mineral imbalances among lime-hating plants, particularly members of the heather and rhododendron family. Dryness can be reduced by laying thick mulches, and by working as much soft organic material into the ground as possible, and repeating this treatment year after year. Rotted lawn mowings or compost made from weeds and leaves, well rotted down, will help moisture-retaining properties, as will developing a good, thick cover of living vegetation. Plant densely on chalk or lime, but be very selective with your plants.
Forget such lime haters as camellias or azaleas and concentrate, instead, on species which look lush but which do well in the dry. Mediterranean shrubs such as Teucrium, Santolina, some of the smaller daphnes, Indigofera, Moroccan broom – Cytisus battandieri – and, of course, lavenders all thrive in lime or chalk.
Take a drive through the Cotswolds, in June, and it becomes obvious which perennials really love the limy conditions. Cranesbills, particularly the larger ones, will flower superbly and will usually seed around freely. Members of the scabious family, such as Knautia, Scabiosa and the teasels will also create spectacular shows for you, especially if you can set them off with tall mulleins (Verbascum,) or perhaps some of the more drought-tolerant foxgloves. Among these, Digitalis ferruginea is a huge favourite of mine, since it develops shapely, dark-green rosettes in its first winter, followed by tall, rusty spikes of flower the following summer.
If you live on heathland, where bracken and heather do well in the surrounding countryside, the chances are, your soil is fast-draining sand. In winter, this is easy to dig in, but in summer, it behaves like the Sahara, losing all its structure and, sometimes, even blowing away on the wind.
Surprisingly, the same treatment that will open up a heavy clay soil will also help to improve moisture-retaining ability of sandy soils. Build and build and build on that organic matter, digging in compost year after year. The results will astound you. Throw nothing away, but rather, compost kitchen waste – as long as it is of vegetable origin – as well as newspapers, weeds, lawn mowings and fallen leaves.
Sandy soil provides excellent growing conditions for annuals. Many, such as poppies, will self-seed prolifically, building up self-sustaining colonies. Californian species such as Eschscholzia are as successful, on sandy soil, as are the lovely European cornfield kinds, and improved garden forms like Shirley Poppies — pink, picotee and lemon – or the intriguing ‘Mother of Pearl’ series whose waving blooms come in dove grey, soft pink and even white. Pot marigolds, cornflowers, and the bushy Convolvulus tricolor are more stocky and bulky in their habits, setting off the ephemeral poppies to perfection, particularly where you have established such drought-tolerant grasses as Festuca glauca or the tall oat, Helictotrichon sempervirens.
Good shrubs are harder to find, for sand, but there are still some dependable ones. In coastal regions, especially where rainfall is high, hardy fuchsia, tamarisk and the larger hebes all do well. But for dry sand, members of the pea family are a safer bet. Common broom, Cytisus scoparius, and its relatives cope well with dry roots, and will grow quite tall. The Mount Etna broom, Genista aetnensis can be grown as a large shrub, or can even be encouraged to develop into a small tree, gorgeous in summer, when its filamentous, weeping branches are hung with golden pea flowers.
ROCKY HORROR SHOW.
Sometimes one ends up with a garden on soil that seems virtually impossible. It might be bare rock, pure chalk – not even with a thin skin of topsoil – or perhaps the ground is so degraded with rubble and builder’s waste that it is almost uncultivable. Even if you are unlucky enough to have inherited such a disappointing garden, do not despair! There is a small and much-treasured cadre of plants that will do, even for you!
You will probably decide to grow the bulk of your garden in containers that way, you can select any soil you like – but there will still be planting opportunities in odd corners and crevices. Among shrubs, the Aucubas can be surprisingly cooperative as long as they can gain a toehold, as is ivy that will grow practically in the dark. Daphne laureola – fragrant, green flowers in late winter, evergreen – seems able to grow in rock crevices, provided it is shaded, and for further winter fragrance, Sarcococca humilis is a shade-loving evergreen which seems happy with little or no root run.
In full light, the little Spanish gorse, Genista hispanica forms neat, rounded, very thorny domes, smothered with yellow blooms in early spring. Carex flagellifera, whose leaves are like pale green horsehair, makes a handsome foil for this, especially when you can contrast its silky texture with the broad, dark-green leaves of Bergenia crassifolia. The hardy bergenias seem happy almost anywhere. Their bright pink blooms, in early spring, are very cheering and the leaves often colour up in winter. Those leaves may be too coarse and leathery for some tastes, but in almost impossible growing conditions, beggars cannot always be choosers!