Pistachio trees (Pistacia vera) have few pests, and growing trees with disease-resistant rootstocks reduces disease problems, but for a harvest of pistachio nuts, you need at least two trees. Slowly growing to 30 feet tall, pistachio trees are hardy in U.S. Department of Agriculture plant hardiness zones 7 through 10. One male tree provides pollen for up to 15 female pistachio trees, and it takes five to six years from planting to the first harvest. Pistachio trees produce their best crops in areas with low humidity where the weather is warm and dry mid to late summer.
The best time for planting pistachio trees is mid to late winter, before new growth appears. Pistachio trees are deciduous and become dormant after they lose their leaves in fall. Planting bare root, dormant trees allows them to establish their root systems as the weather slowly warms up in spring. You can also plant pistachio trees in containers in late spring through early summer.
Growing spots for pistachio trees must receive at least eight hours of direct sunlight every day. Pistachio trees produce deep roots and tolerate most soil types but grow best in deep, crumbly, freely draining soil. They tolerate alkaline and slightly acidic soil, and coastal, saline soil.
Wide planting holes help pistachio trees establish quickly.
- Dig a hole twice as wide as the root ball of a tree and the same depth.
- Mix aged manure or compost into the removed soil at a rate of 1 part manure or compost to 19 parts soil.
- Remove the container or burlap covering and twine or wire.
- Place the tree upright in the hole at its original growing depth.
- Scoop the dug soil into the hole to fill the gaps around the root ball until the hole is full.
- Press the soil with your hands to firm the tree in the ground.
- Water the soil over the root area with a garden hose fitted with a soft spray attachment until the water begins to puddle.
Check the tree from all sides to be sure it's vertical.
Pruning the central stems of pistachio trees after planting provides a good growing form. After planting, prune the central stem above the lowest four or five thick, healthy side shoots. Prune just above the highest of the shoots.
Wipe pruning shear blades with a cloth soaked in rubbing alcohol before and after pruning pistachio trees to prevent spreading disease.
Watering Pistachio Trees
Pistachio trees tolerate drought, but deep, infrequent watering encourages good growth. Water pistachio trees when the soil is dry to a depth of 2 inches. Apply 2 or 3 inches of water or enough to moisten the soil to the depth of the root ball.
Don't water so much that the soil becomes soggy. Pistachio trees suffer root diseases in wet or poorly drained soil.