Trees and plants are like children. You get out of them what you put in to them. Care should be taken not only in selecting the plant, but in the planting as well. Dig a hole twice as wide as the pot size. The more sandy soil, the more organic matter such as Black Kow composted Manure or Mushroom Compost. The organic matter will increase the water the soil can hold in reserve, and help feed the plants. Make sure you blend the in the organic matter, or it will act like a sponge and become a reservoir for root fungus problems. Do not use fresh manure or put fertilizer in the planting hole, as this can burn the roots of the plant.
When you remove the plant from its pot, check and see if the roots are circling around the outside of the soil on the rootball. If so, gently massage or slice the roots to loosen them so they will spread out into the new hole. Plant at slightly higher level then the plant sat in the pot, compared to the surrounding garden. The larger diameter the rootball, the higher it should sit when you are finished planting. This will ensure that the trunk of your tree or shrub is not the lowest point in the area. If the trunk sits with puddled water, soil or mulch around the bark, this will cause rotting of the trunk and the death of the plant. Before backfilling, water thoroughly (large trees will need watering several times). A dry rootball that is planted without this initial proper watering, will never become sufficiently moist to ensure survival. Once the water has drained away, finish your planting, water again to settle any air pockets. Fertilize with a balanced time-released fertilizer, and mulch. Hand-water as necessary for the first 2 to 3 weeks after planting. This may be every day or two initially, and then, every few days for two months after that. DO NOT rely on automatic irrigation systems for establishing new plants. They do not water sufficiently or evenly, no matter who you had install them.