Book excerpt: Whether you are a beginning or experienced gardening enthusiast, a student of gardening, or a horticultural professional, 'The Why and How of Home Horticulture: Second edition' will prepare you to face virtually any gardening situation. Like no other gardening book, it supports its practical, how-to-do-it guidelines with clear explanations of the relevant scientific principles of horticulture. You will know what steps to take--and why those steps are working.