Question: We have nine pine trees, and they are dropping lots of needles. We have a large berm under the trees and water inside the berm twice weekly. Should the needles be removed or left inside the berm?
The needles are fine. If composted, they are said to be slightly acidic and will benefit our alkaline soils. If they are left alone in the basin, they will help mulch the soil, conserve water, reduce weed emergence and benefit the soil in general.
A lot of needles blew out of the trees during the last storm event we had. This is a normal occurrence and nothing to worry about.
If pine trees are getting plenty of water and fertilized once a year, they will have a thick, lush canopy and grow about 12 to 18 inches a year. If water is not enough, they will not grow as much and not have a dense canopy. They will survive like that but just not be as thick and lush.
Your berms should extend three to four feet from the trunk and be deep and level enough to hold about 3 to 4 inches of water. Your watering frequency sounds right. Just make sure it gets enough water each time to move into the soil two to three feet or more. In sandy soils, water needs to go deeper and more often.
Bob Morris is a professor emeritus in horticulture with the University of Nevada and can be reached at email@example.com. Visit his blog at