Watering Your Landscape
The most critical time for a newly installed or transplanted plant is the first month or two. It is very important for a plant to have regular moisture at this time. Plants can get moisture through rainfall, manual watering, automatic irrigation systems, or other watering aids.
Rain is the most effective means of water for plants. Rain water is highly oxygenated, and a slow rain soaks the ground much more effectively than sprinklers or irrigation systems. However, rain isn't dependable and so other means are often required. Also, while a good standard for lawns and plants is one inch of water per week, thunderstorms can deposit an inch of rain or more in a very short period, yet the ground is dry 30 minutes later. Rain often runs off instead of soaking in, and you must be aware that this doesn't satisfy the needs of your plants.
Manual watering can be effective if its not hurried. The least effective means of watering, and the cause of many dead plants, is watering by holding a hose over the plant. When doing this, most of the water flows away and the water does not get the soil deep more than a half inch down. You've wasted your water and time. If you must hand water from a hose, you'll need to stand over each plant for a couple of minutes to be sure you've supplied enough to soak in. It is much more efficient and helpful for the plant to use a sprinkler or soaker hose.
Irrigation systems can be very effective in maintaining proper moisture for plants and lawns if the system is setup properly. A system where a zone covers plants and lawn can be effective in watering one of them, but not both. Most irrigation companies will segregate planting and lawn zones so that they can supply the appropriate amount of water with the correct timing to each. Best irrigation practices should include moisture sensors that will skip watering if adequate moisture is present.
Without an automatic irrigation system, everyone relies on some form of watering aid to help water their landscape. Sprinklers can be used to water lawns and landscape as long as they are left on long enough to supply enough water and the sprinkler is moved around to give good coverage. The amount of water can be determined by placing a coffee can or other container under the sprinkler, and measuring the amount in the can. Soaker hoses are more effective for watering plants than sprinklers because the water goes directly into the soil, and little is lost to evaporation. Soaker hoses are not as effective on larger areas of lawn. Gator Bags are plastic bags that gently weep water over a period of hours and are very effective in watering trees and large evergreens. They must be filled from a hose when empty, and can be quite heavy to carry around if your hose doesn't extend out to them, but they do a great job of supplying water to larger trees. Water holding crystals expand when wet and hold water longer than the surronding soil. The water is slowly released into the soil. We often use these when we have a situation where we know that other means of watering are impractical.
Links
Effective water use
Landscape pest control
Landscape bed maintenance