Knowing your soil type is important when planning a garden. It is best to choose plants that thrive in the natural soil rather than trying to dramatically amend it. While home gardeners may describe their soil as loamy, heavy or good, scientists prefer to group soil types into three broad categories based on the soil's texture: sandy, silt, and clay. Loam soil contains all three of the textures.
Sand is composed of the largest particles of the three soil types. They are easily seen with the naked eye and feel gritty to the touch. Sand is made up of ground-up particles of minerals and rocks. Water drains well in sand, which is why sand often is added to heavier soils to aid in draining. Pure sand, however, drains too rapidly for most plants, and it does not retain nutrients well. Consequently, plants in sandy soil should be drought-tolerant. The broom shrub, hibiscus, tulips and the sun rose all fare well in sandy soils.
Silt is smooth and slippery to the touch. It is composed of very fine particles of minerals and rocks; primarily quartz. Silt holds water and nutrients very well and is not as sticky or as heavy as clay. Silt is great for plants that like a lot of water. New Zealand flax, the mahonia shrub, hakonechloa and the showy tobacco plant are a few examples of plants that can thrive in silt.
Clay also is composed of tiny particles of rocks and minerals. However, these particles are extremely fine and closely packed. While this allows clay to retain water and nutrients, it also makes it quite heavy and hard to work with. Clay holds water too well; it can cause roots get waterlogged and rot. Clay soils can be so hard that the roots of the plants have a hard time growing through it. Still, there are some plants that will grow well in clay soil. Apple and willow trees do very well in clay, as do the popular and fragrant honeysuckle and lilac bushes. Arborvitae, winterberry, snowberry and sumac also thrive in clay soils.
Loam is a mixture of all three types of soil and is the recommended type of soil to use in the garden. Loam usually has organic matter added to make it even more nutrient-rich. Loam is loose enough to drain water but tight enough to retain enough water for the plant to grow. Most loams have one of the three types of soil predominant. For example, soil may be classified as "sandy loam", meaning it has more sand in it than silt or clay. Gardeners recommend planting in loamy soil whenever possible. According to the master gardeners at BBC gardening, loamy soil is the most fertile type of soil. Vegetables grow best in loamy soil, as do all annual flowers. Wisteria and other summer flowering perennial vines should also be planted in loamy soil.