Root systems in almond trees may seem like a basic part of the business for growers with years of experience, but Astrid Volder, a UC Davis professor and root physiologist, had some in-depth information when she spoke with growers in Modesto.
For starters: While almond tree root systems can extend twice the height of the tree, most of those systems spread horizontally and are not very deep.
“The root system extends way beyond the crown of the tree,” Volders aid. “So in your orchard, those whole areas are basically covered in shallow root systems.”
She compared fine roots to leaves: Volder said those roots are constantly taking nutrients up, replenishing the tree’s supplies.
One mistake she sees visiting orchards is over-tight staking.
“If you are staking your tree very tight and you’re not allowing that tree to move, you’re not allowing those roots to grow (as much as they could),” Volder told growers.
If a tree can move some, it grows more lateral roots and grows them deeper.
Another important fact: For almond tree roots, the median lifespan is 3 or 4 months.
“They turn over rather quickly,” Volder said. “They’re being produced throughout the growing season.”
She said new root production mainly occurs between late March and August and September.
“You want to fertilize when you are having a high amount of root production,” Volder told growers.
Volder warned against overwatering.
“When you water a lot, you’re pushing all the oxygen out of the soil, and roots are not getting enough oxygen,” she said. “If you want high rates of root growth, you have to have oxygen in the soil.”
One thing Volder told growers to watch out for when planting new orchards is root quality in trees purchased from nurseries.
In some cases, trees may have circling root systems that can choke the tree once it’s in the ground. That problem doesn’t self-correct after the tree is in the ground, she said.
“If you have problems at the center of the tree, it’s very very difficult to correct,” Volder said.
Growers should cut root circling patterns out of the root ball, but if it’s close to the main stem and many trees bought from the nursery show the pattern, it should be returned and exchanged, she said.
A final tip for new orchards?
Growers shouldn’t spread field soil on top of a new tree’s root ball--that top layer can absorb water and redirect it around the root ball.