Most plants need regular watering to survive, and even the most drought-tolerant plants need water from time to time. Many factors come into play when determining how best to meet a garden's water needs.
Drought-tolerant plants, lawns, perennial beds and edible gardens require different amounts and frequency of watering. When planning your yard or garden areas, think ahead about how much water individual plants need and group similar plants together. This will make it easier to manage watering (and save water) by ensuring that all plants in the same area are watered at the same frequency. It also helps keep neighboring plants healthy by not overwatering dry-loving plants and overwatering water-loving plants just because they are next to each other. Also, remember that the shallow roots of annuals will need to be watered more often than deep-rooted perennials.
Does your garden get a lot of sun or is it in the shade?
Evaporation from bright sunlight can reduce precious water use in a sunny garden by as much as 50%. Areas in the shade retain moisture longer and may become waterlogged. Define different areas of the entire yard or garden. Drip or evapotranspiration irrigation would probably be better in full sun areas, as well as windy areas. Zones that are constantly in shade should have a different schedule than those that are in full sun because they will be overwatered more quickly than hotter, drier zones.
What is the composition of your soil?
Sandy, clayey, rocky, these soils all affect how well water is absorbed and ultimately drained from the area.
Clay soil is often called heavy. Water is absorbed slowly and distributed, and clay can hold a lot of it. It is best to water clay soil slowly so that it soaks in. Dry clay soil tends to crack and roots can have difficulty penetrating it. The best additions to clay soil are compost or organic matter that improves drainage.
Sandy soil allows water to soak directly into the ground without holding much water. Plants will need to be watered more often and in a wider arc to spread out the roots. The best amendments are compost or organic matter that helps retain moisture.
Loam soil is a combination of sand, silt, and clay that is best suited for plant growth. Loam is rich in nutrients, distributes water evenly, and drains well.
Most gardeners answer these questions in a variety of ways - some areas may be in sun and some in shade, there may be a mix of flat surfaces and slopes, and some areas may be windier than others. Knowing all of these factors will help you best choose the right garden irrigation system (or combination) for your individual needs and garden area.