Making the Most of Your Garden Soil

Learn how to make various types of soil work in your outdoor space.

By: DK Books - Garden SXS
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Different types of soil have differing characteristics, some aiding cultivation of certain plants, others providing a challenge to gardeners. Various techniques can be used to improve the soil to maximize its potential.

Alkaline Soil


Alkaline soil enables you to grow a wide range of plants; many vegetables (such as members of the cabbage family) will not grow as well in acidic soil. Ornamentals, such as clematis, are said to grow better in alkaline soil, and the finest rose gardens tend to be in alkaline areas. This soil suits earthworms; some pests and diseases, such as clubroot, are less of a problem.


There are certain plants that simply will not grow in alkaline conditions and, unfortunately, they are often among the most desirable. Rhododendrons, camellias, Pieris, some magnolias and other woodland plants, such as Uvularia and Trillium, need the cool, moist, acidic soil associated with their native habitats. These plants are known as “calcifuges” or lime-haters. Some acid-loving plants may survive in alkaline soil but will look sick, with yellowing leaves (chlorosis). Alkaline soil tends to be deficient in manganese, boron and phosphorus, all of which are important for healthy plant growth.

Improving Alkaline Soil

You cannot, as such, improve alkaline soil, since a high pH can be both good and bad. Gardeners are advised to grow what suits their particular soil. Many acid-loving plants can be grown in containers, or in a raised bed filled with ericaceous (acidic) compost. Where the soil pH is neutral or just alkaline, years of adding organic matter may lower the pH enough for some smaller acid-loving plants.

Consider these plants for alkaline soil:

  • Aquilegia McKana Group
  • Aster ‘Coombe Fishacre’
  • Buddleja davidii ‘Dartmoor’
  • Buxus sempervirens
  • Choisya ternata Sundance
  • Clematis
  • Cotoneaster horizontalis
  • Erica carnea ‘Foxhollow’
  • Erysimum ‘Bowles Mauve’
  • Hebe
  • Hibiscus syriacus ‘Oiseau Bleu’
  • Iris unguicularis
  • Lavandula stoechas
  • Mahonia x media ‘Buckland’
  • Nepeta x faassenii
  • Phormium ‘Yellow Wave’
  • Primula vulgaris
  • roses
  • Salvia officinalis 'Purpurascens'
  • Sedum 'Herbstfreude' 

Acidic Soil


Some of the most spectacular garden plants, including rhododendrons, Meconopsis and Desfontainia, will grow well only in acidic soil. Other species, such as Hamamelis, may survive in alkaline soil but simply perform better in acidic soil. Few garden plants will not tolerate mildly acidic soil, although a very low pH will limit your choices. Acidic soil is often associated with woodland conditions and tends to be cool and moist.


Acidic soil, though usually rich in organic matter, can be quite poor, especially if it is also sandy. To improve it, dig in plenty of well-rotted manure each year. Very peaty soil can, conversely, be waterlogged and require draining. This is often the most acidic of all and you may need to add lime to it for a range of plants to thrive. Most fruits and vegetables do not like strongly acidic soil and other plants simply will not grow — these are known as “calcicoles” or lime-lovers. Acidic soil is often deficient in phosphorus and may have too much manganese and aluminum for healthy plant growth.

Improving Acidic Soil

If your soil is strongly acidic, you may need to increase the pH to broaden the range of plants you can grow. Adding spent mushroom compost is an excellent way of doing this. Powdered lime is an alternative. However, most gardeners usually feel that mildly acidic soil is desirable, and simply grow plants that enjoy their conditions.

Consider these plants for acidic soil:

  • Astilboides tabularis
  • Betula (birch)
  • Camellia
  • Cercis canadensis ‘Forest Pansy’
  • Cornus canadensis
  • Corydalis flexuosa
  • Daphne bholua ‘Jacqueline Postill’
  • Desfontainea spinosa
  • Digitalis purpurea (foxglove)
  • Hedychium densiflorum
  • Leucothoe fontanesiana ‘Rainbow’
  • Meconopsis
  • Photinia x fraseri ‘Red Robin’
  • Pieris
  • Primula pulverulenta
  • Rhododendron
  • Romneya coulteri
  • Skimmia x confusa ‘Kew Green’
  • Stewartia monadelpha
  • Uvularia grandiflora

Sandy Soil


Sandy soil is free-draining, which prevents plants from becoming waterlogged in winter and aids the survival of species sensitive to wet conditions. It is easy and light to dig all year, and warms up quickly in the spring. 


In dry conditions, plants will often require extra irrigation, and moisture-loving species will be unreliable in this soil. Sandy soil has a tendency to be poor, so you will need to apply plenty of plant food and organic matter. 

Improving Sandy Soil

Dig in large amounts of organic matter each year to help improve the soil‘s ability to hold water and nutrients. Mulches such as gravel help to keep in moisture. Digging in clay may also be useful.

Consider these plants for sandy soil:

  • Acacia dealbata
  • Calluna vulgaris ‘Silver Knight’
  • Catananche caerulea
  • Cistus x hybridus
  • Convolvulus cneorum
  • Cotoneaster horizontalis
  • Erysimum ‘Bowles‘ Mauve’
  • Euphorbia characias
  • Euphorbia rigida
  • Grevillea ‘Canberra Gem’
  • Helianthemum ‘Rhodanthe Carneum’ (‘Wisley Pink’)
  • Helleborus argutifolius
  • Iris unguicularis
  • Melianthus major
  • Olea europaea (olive)
  • Pittosporum tobira
  • Romneya coulteri
  • Rosmarinus officinalis (rosemary)
  • Solanum crispum ‘Glasnevin’
  • Verbena bonariensis

Clay Soil


Clay soil is usually highly fertile and many plants thrive in it. It also retains water well. The more clay soil is worked, the better it is for planting, as the soil gradually becomes more crumbly and drainage improves. Avoid working the soil when it is wet and easily compacted.


Despite its high fertility, clay soil has a number of problems that can be hard to tackle. In winter it may become waterlogged and impossible to dig. Attempts to work the soil in this state usually create compaction, where the soil particles are compressed, resulting in yet further waterlogging. In summer, the opposite problem occurs; clay bakes hard and even simple digging can be impossible. Even when the soil is manageable, it is heavy, breaking into large clods, and it is slow to warm up in spring.

Improving Clay Soil

The key to success is often simply perseverance. By adding organic matter to the soil, you will eventually improve its structure, making it more crumbly and easier to work. In small areas, perhaps in a raised bed, dig in horticultural sand. Avoid walking on the garden when it is waterlogged and do not dig the soil when wet. Try to carry out most planting in spring or fall when the soil is more manageable. In areas where waterlogging is severe, you may need to install drains.

Consider these plants for clay soil: 

  • Alchemilla mollis
  • Arum italicum subsp. italicum ‘Marmoratum’
  • Aruncus dioicus
  • Aucuba japonica (spotted laurel)
  • Berberis darwinii
  • Buxus sempervirens (box)
  • Campanula glomerata
  • Carex elata
  • Cornus sanguinea ‘Winter Beauty’
  • Digitalis purpurea (foxglove)
  • Geranium
  • Hemerocallis (day lily)
  • Hosta
  • Hydrangea macrophylla ‘Lanarth White’
  • Iris laevigata
  • Jasminum nudiflorum
  • Leycesteria formosa
  • Mahonia x media ‘Buckland’
  • Viburnum tinus ‘Eve Price’
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