Spring, after all possibility of frost has past and before the heat of the summer, is an ideal time to plant citrus trees.
Proper planting of fruit trees is critical to their long-term health and productivity; many issues that plague trees over years may be avoided by selecting a healthy young tree that isn’t rootbound, and planting it properly.
Citrus and other fruit trees are often planted too deeply in nursery pots, and then are planted too deeply in the ground when gardeners follow the common nursery advice of planting trees at the same level that they were in the nursery pot. Planting trees too deeply can result in lifelong problems, from weakened immune systems that lead to disease and pest problems, to poor yields, poor anchoring, and tree failure.
How to recognize the depth at which a tree should be planted: Trees prefer to have a root flare and buttressing roots at grade, or at about even to slightly above or slightly below ground level. When preparing to purchase or plant a fruit tree, move soil away from its trunk inside the nursery pot until you find the first significant root. That root should be placed at about grade. In many instances, the first significant root is several inches deep in the nursery pot; this means that the tree has only a very shallow root system, and is therefore an inferior tree. Ideally you should rule out such trees before purchasing, as they will need staking and may be slow to establish and have persistently shallow root systems for the first few years after planting.
Before beginning to dig your hole, determine the depth of the tree’s root ball. This is the distance from the highest significant root to the bottom of the roots. For some trees, this may be only 1 to 3 inches, despite there being an unrooted section of trunk buried in 10 inches of soil in a 5-gallon nursery pot.
Dig your planting hole about twice as wide and slightly less deep than the tree’s root ball. This may mean your planting hole will be only a few inches deep. Do not dig a deep hole or loosen soil at all to a depth greater than the specific rootball of the tree that will go into that hole. Loose soil and holes that are too deep lead to the tree sinking after planting as soil settles. Being planted too deeply often results in lifelong stress for trees, and encourages a variety of problems and issues that you might never associate with inappropriate planting or planting too deeply.
The only time that GardenZeus expert Darren Butler encourages compacting soil is at the bottom of planting holes for woody plants and trees. Use a tamper or jump up and down on the bottom of your planting hole to compact soil as much as possible. A small section of compacted soil beneath the center of a young tree will not harm it, but a tree that sinks even an inch or two may have lifelong difficulty.
Gently remove the tree from the pot. Loosen and spread roots that are bunched or have started to circle. Citrus are evergreens and soil should never be removed from their roots. As much as possible, prevent soil from falling off the rootball, as this can shock the tree. Citrus trees should generally be planted above grade by 1 to 2 inches, with soil mounded to cover roots. This compensates for soil settling, provides good drainage for upper roots, and reduces risk of diseases and other issues.
The hole should be backfilled with the same soil that was removed, with clods broken up to prevent air pockets that inhibit or cause drying of roots; and without any compost, organic matter, manure, or other amendments. To develop into a strong mature tree, your young tree needs to anchor itself deeply and send roots out into the surrounding soil to obtain nutrients and to become part of the soil ecosystem. Providing rich or amended soil in the planting hole allows the tree to obtain all the nutrients it needs within a small area, and encourages a smaller root system and/or girdling roots, which may lead to a slow-growing, water-stressed tree that is prone to failure in wind or under its own weight in years to come. After backfilling, tamp soil gently or press with feet to eliminate air pockets beneath the soil.
Apply compost, manures, and other amendments in the form of surface dressing, covering the soil surface to within a few inches of the trunk and to a radius of 2 to 3 feet around the newly planted young tree, and cover with mulch. This will encourage a healthy soil ecosystem that will support the tree’s establishment, and will require the tree to grow a strong root system to obtain the nutrients and water that it needs.
Water thoroughly after planting to prevent water stress and to eliminate air pockets beneath the soil.
Stake trees only if they cannot stand up on their own; generally it’s preferable to prune more aggressively if this allows staking to be avoided. Staking is undesirable because trees need to move with wind, and biologically need the strain from their own weight and natural movement to grow strong trunks with good taper and caliper. If staking is necessary, never use a single stake close to the trunk; instead, use 2 stakes spaced 6 to 12 inches or more from the trunk, with overlapping ties that allow the trunk a few inches of movement. Move stakes progressively further from the trunk over time, and allow additional movement with looser ties. Ideally, stakes should be removed as soon as the tree has established sufficient roots to stand on its own, often within 6 to 12 months of planting. Stakes that remain too long often cause physical injury that leads to decay. Trees that have depended on stakes for too long often have weak trunks and may fail as a result, particularly when stakes are removed.
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