Answer: Not only do root systems help feed a tree, they help to anchor the tree in the ground. It sounds as though the root system on your lemon tree is insufficient for the size and weight of the canopy and the fruit it has developed. Sandy soil is good in the respect that it drains quickly, but it can make getting a good grip difficult for the roots of your tree.
Stake your tree before it falls over completely! Three stakes will safely protect the tree from most situations.
The stakes should be placed securely in the undisturbed soil adjacent to the root ball where there will be no damage done to the roots. Wooden stakes of 2 inches in diameter are ideal and should be placed equal distances from one another to form a triangle. A single tie placed near the top of each stake and placed around the tree in a figure 8 should be sufficient support. Any material used as a tie should contact the trunk with a broad, smooth surface and have enough elasticity to minimize trunk abrasion and girdling. Common tie materials include wire covered with hose or tubing, polyethylene tape, belting and elastic webbing.
Adjust the ties as necessary to avoid damaging the bark, and try removing the stakes after about a year. If your tree needs further support, you can always stake it up again, but constantly staked trees tend to remain weak and dependent upon support.
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