PALM ROOTS

[Robert Lee Riffle]

Many posters ask if palm roots will damage concrete in the same way that other trees, like Ficus, do.  The fear is that a palm planted too near a sidewalk, etc., will heave the concrete.

The answer is no, and here’s why:

Palms are often called trees, but they’re only trees sometimes in height.  They are monocots and are really related to giant grasses like bamboo, which are also monocots. This means, among many other things, that they have one seed leaf when their seeds germinate, as opposed to two seed leaves for dicots.  

Another difference between monocots and dicots is that monocot structures do not so dramatically increase in size once the given plant is past the juvenile or seed leaf stage.  In other words, a bamboo culm or palm tree stem (trunk) will stay much more nearly the same size it was when first formed than will a dicot stem.  Monocot roots act the same way.  Palm roots form from a “basal plate” at the base of the trunk and stay more or less the same diameter all along their length for the life of the palm.  Chop a palm root, and it might sprout from where you cut it, or it might regrow from the basal plate.  

On the other hand dicot tree structures usually do get much larger with time.  That’s why an old oak tree will have a massive trunk; it keeps adding rings of wood as it grows and ages  Dicot roots do the same.  Like trunks, they get larger with time.

A dicot root will work its way through a crack in the concrete or a stone wall, and, if it finds water and/or nutrition on the other side, witll get fatter and fatter with time.  A palm root will work its way through the crack and not get any fatter.  The concrete is safe.

Dave from So-Cal, 07/08/09

[DoomsDave]

This is instructive!

[Pando]

I have seen examples (including my own yard) where concrete walkways have moved due to palm roots. While the roots don't get fatter over time, they still have to go somewhere, displacing soil. A mass of palm roots going underneath a concrete pad can move it vertically, especially thinner walkways without reinforcement wire.

My old A. cunninghamiana has lifted a concrete slab walkway 2 feet away from the trunk about 1 inch vertically in one side, tilting it, and it's clearly visible against the adjacent slab.