Question
QUESTION: I have recently read that this tree has a suffocating root system.  I planted one two weeks ago at the edge of my vegetable garden.  I dug a very deep hole in attempt to get the roots to go straight down before spreading out.  I plan to water very deep once a week as well.  Will this tree eventually take over the garden?
ANSWER: If by a suffocating root system you mean that the roots are thick and fibrous you are right. They will compete well with the other plants for the space.
A mature avocado can reach 40 feet in height and width. The roots of the tree can extend 60 feet in all directions (but that's just a potential; actual growth will depend upon soil conditions). Give your avocado tree as much sunlight and elbow room as possible so it doesn't become overcrowded as it matures.
Roots of mature avocado trees spread beyond the drip-line of the tree canopy and heavy fertilization of the lawn adjacent to avocado trees is not recommended and may reduce fruiting and or fruit quality. The use of lawn sprinkler systems on a timer may result in over watering and cause avocado trees to decline. This is because too much water, too often is being applied which results in root rot.



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QUESTION: How far down will the roots go before spreading out?  Do I have to worry about the roots eventually invading my semi raised vegetable garden?  if I till the dirt once a year in the beds, will that keep the roots in check, make them go deeper maybe?  The soil i planted the vegetables and the tree in is very good dirt.  The surrounding area consist of hard compact clay.  I am trying to avoid a future nightmare if possible.  Thank you!

Answer
The roots will spread as far as the foliage at the very least. they need this spread to hold the tree up. They will go down into the soil but you will still have the majority of the root system in the area of the foliage cover. Tilling the soil away from the tree will limit the root and in turn will also limit the growth of the tree. So you will have a smaller tree than normal. It would be like putting plant in a pot and the plant grows until it gets root bound and then it slows or just stays the same size. This is essentially what the folks do when they want a bonsai tree. Avocado tree maybe too large for the area you have for it IF you let it grow to it natural size.