Healthy gardens require ongoing attention to threats from pests and diseases, ideally through a holistic approach known as integrated pest management (IPM). IPM begins with prevention and careful monitoring, escalating to controls only when needed and favoring the least-toxic options. Beneficial insects play a major role: ladybugs, lacewings, ground beetles, parasitic wasps, and hoverflies prey on pests or pollinate crops. Birds eat insects and other pests, though they sometimes sample fruit as well. When pests do appear, gardeners can hand-pick caterpillars and slugs, drape lightweight row cover fabric over plants to exclude pests and frost, or apply targeted organic controls like neem oil, Bacillus thuringiensis (Bt, a bacterium that affects only caterpillars), or diatomaceous earth, a powder made from fossilized algae that abrades insect bodies. Trap crops attract pests away from main plantings, and companion plants like marigolds can repel certain nematodes while basil helps deter tomato pests.
Plant diseases are caused by pathogens including fungi, bacteria, viruses, and nematodes. Common examples include powdery mildew, downy mildew, blight, rust, leaf spot, and root rot. Cultural practices prevent most outbreaks: good air circulation dries foliage and discourages fungal growth, removing diseased material through crop hygiene prevents spread, and solarization—covering moist soil with clear plastic for several weeks—uses solar heat to kill soil-borne pests and pathogens. Strong, healthy soil grows strong plants that resist pests and diseases more effectively, making soil health itself a form of pest prevention.
Water management is equally vital. Xeriscaping, or water-wise gardening, uses drought-tolerant plants and minimal irrigation to reduce water use, suiting xeric (drought-loving) species, while mesic plants prefer moderate moisture and hydric plants thrive in wet conditions. For most gardens, deep watering—watering thoroughly but less often—encourages roots to grow downward in search of moisture. The best time to water is early morning, when evaporation is low and foliage dries before nightfall. Drip irrigation and soaker hoses deliver water directly to the root zone with minimal waste, while mulch conserves moisture by reducing evaporation. Rainwater harvesting collects rain in barrels, and greywater from sinks and showers can be reused on ornamental areas. Signs of overwatering include wilting, yellow leaves, root rot, and fungal growth, while underwatering produces wilting, dry soil, brown leaf edges, and slow growth. The simplest diagnostic tool is the "finger test"—sticking a finger one to two inches into the soil to feel for moisture before deciding whether to water.