By the time you read this there should be little question in anyone's mind that summer is on its way. Care of boxed landscape trees at the landscape construction job site is always tricky. With the addition of desert summer conditions, careless on-site storage of boxed trees can severely damage and even kill trees. In an ideal world boxed trees would be planted on the same day they are delivered to the job. In this way trees remain in the nursery where they receive regular, automated irrigation and fertilization along with normal production yard care right up until the time they are planted. In the nursery trees are removed from drip irrigation the day before they are delivered and hand watering begins. Scheduling problems, weekend work, delays caused by other trades and countless construction site disasters can work to prevent timely planting of trees. Once on the job site many thing can happen that compromise the vigor and survivability of boxed trees. Irrigation is critical to the survival of trees stored at the job site. Its important to appreciate that under nursery conditions trees are given from 2 to 3 slow drip irrigations per day during the summer. Under these conditions the root mass (tree roots and the growing medium) is never allowed to completely dry out. Water is applied using a metering dripper or a spray-type nozzle to deliver water. These application methods provide a slow, well distributed supply of water over an extended period of time.
Summer irrigations are also used to deliver liquid fertilizer to the tree through the drip system. Irrigation and tree care are the primary focus of work in the nursery. On the job site, tree care is only one of numerous tasks landscape construction professionals must perform. If trees receive insufficient water the entire root mass shrinks and the planting medium can pull away from the inside of the box. When water is then reapplied to dry boxes the water can run down these separations and out the bottom of the box with little water being absorbed by the root mass. The irrigator, seeing water running out of the bottom can falsely assume that the tree has been well watered.
Trees watered using a hose must be watered regularly, SLOWLY and frequently. In the nursery, trees typically receive (by drip irrigation) the following volume of water per day in the summer:
Tree boxes are often filled to near the top with planting mix leaving a very limited irrigation basin. Filling these basin quickly does not provide sufficient water to sustain the tree.
The logistics of every job site are unique making it impossible to suggest specific irrigation schedules. It is safe to say that in the late spring, summer and early fall months, multiple irrigations per day are appropriate. Its also important to appreciate that on some job sites transpiration, the rate at which plants release water through the leaves, may be much higher than under nursery conditions. In hot weather trees stored on the job site over the weekend should be watered a minimum of once a day. Trees left over a weekend without water may not be worth planting come Monday.
TO SUMMARIZE: Avoid storing trees at the job site, schedule deliveries to allow timely planting of trees, set stored boxed trees on level ground, keep boxes "dished out" to help retain water in the top of the box; water should be applied to regularly, uniformly and slowly, the root mass should never be allowed to dry out.
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