Your new trees, shrubs, and/or perennials require special attention for at least one month after planting, until the root systems get a chance to grow out into the surrounding soil. A little vigilance in ensuring that each plant receives its full allotment of water during this time is the single most important factor in determining the future success of your plants. Keep in mind that the root balls of your new plants will dry out just like a houseplant even though the surrounding soil appears wet. The best way to check the roots is to pull away the mulch from the stem of the plant and use your finger to scrape down an inch or two directly into the rootball to feel for dryness.
Sprinkler systems, even the best ones, will water some areas better than others. After your landscape has had time for the plant roots to spread out and intermingle (at least 6 weeks after planting), this unevenness in sprinkler coverage is not a major problem. But when the plants have just been installed, some plants may not receive enough water from the sprinklers to survive the critical first few weeks. For this reason it is imperative that you make frequent (daily to every second day) inspections of your landscape so you can spot plants that may be dry, and water them by hand to give them the opportunity to grow roots into areas that get more water.
Following the guidelines below as a supplement to your sprinkler system will help integrate your plants quickly into the landscape:
A. Shrubs and Perennials – by hand with hose and/or bucket
1. First week – Water every 2 days for shrubs and perennials in full sun, every 3-4 days if in shade. Under extremely hot or windy conditions in full sun, you may need to water every day. Treat them like house plants and aim the hose directly into the root ball. Make mental notes of areas that seem to need extra attention.
2. Next two weeks – Water your extra-attention areas as above. For the areas that are not a problem, water once a week just to be sure.
3. After 3 weeks – Your new shrubs should be somewhat established. Continue to water your extra-attention plants once a week by hand until the end of the season as a supplement to your sprinkler system.
B. Trees and Large Shrubs – by hand with hose or bucket
1. First two weeks – Water by placing the hose directly on the root ball, then turning on the faucet so that the water comes out in a slow trickle. Let it trickle for ¸ -1 hour for each plant. The larger the tree and the more exposed it is to wind and sun, the more time needed. Look for special-attention plants. Repeat every 5-7 days depending on weather and sunlight conditions.
2. Next four weeks – Water twice as above during this period.
3. After six weeks – Water those special-attention plants during extended periods of no rainfall occasionally as above until the end of December.