It should also have about five per cent organic matter or humus-the magic ingredient that enables soil to both hold moisture and drain well. Humus is the decayed remains of once living material, most commonly plant residues and animal manures. You can make it by composting dead plants, kitchen scraps and fall leaves, or you can buy composted manure or compost. In sandy conditions, humus acts like a sponge to hold moisture, while in clay, it breaks up small particles to create larger spaces that drain more easily and hold oxygen for plant roots.
Oddly enough, the best way to improve almost any kind of soil is the same: spread about five to seven centimetres of humus over the garden bed, then work it in-it's worth the effort.
Landscape Planning: Practical Techniques for the Home Gardener by Judith Adam, Firefly Books, 240 pages, softcover, $27.95
Perennials for Every Purpose by Larry Hodgson, Rodale, 502 pages, softcover, $29.95
Secrets to Great Soil by Elisabeth P. Stell, Storey Publishing, 224 pages, softcover, $29.95