Magnolias don't have roots like most other trees. Their roots never have that fine nearly microscopic thread like phase, where they work their ways into cracks and under patios, etc. only to later thicken and become woody causing damage. Magnolias roots are thick, relatively soft and fleshy from the get go and never become fully woody, so they shouldn't be of any risk in damaging a patio.

I noticed that both the linked study and the other study it referenced were done on the West coast. I'm a bit skeptical on the information regarding Magnolia grandiflora, since every other study I've read(all done in the SE US) don't show M. grandiflora as having any potential for causing damage. Also, from just a pure anecdotal evidence, I've seen plenty of M. grandiflora planted as street trees right next to sidewalks in the Los Angeles area, and San Francisco area and have yet to notice one causing any sidewalk damage. Have you seen any causing damage in your area brandon7?

Whatever damage a M. grandiflora may or may not cause, a M. virginiana (Sweetbay) is a very different tree, and I think the likelihood of it causing any damage to anything is slim to none.

Perhaps more to the point, I suspect putting down a hardcore patio like this would damage the tree's roots, and quite possibly kill it.

Resin

Kman,
I have seen M. grandiflora lift sidewalks and borders around beds.

Laceyvail,
Assuming your right about the M. virginiana, having half the patio unaffected doesn't seem like it would be that much of a positive (unless your an optimist).

on tuesday, my backhoe guy mistakenly cut through and removed a 12" piece of tree root, 3" in diameter. this is a tulip magnolia, northern new jersey, zone 6A. does anyone know what i can do to keep this from harming or killing the tree? thanks very much.

Srosso,

You might want to start your own thread in situations like this. Starting your own thread will eliminate bothering the OP with responses unrelated to their original concern, save all of us the time required to read through the old unrelated messages, make future searches for information more productive, and allow you to directly receive responses.

In any case, the relative damage will partly depend on how big your tree is. If you are talking about a single root from a large, mature tree, I wouldn't worry too much about it. If you still have access to the damaged area, you could clean the damaged area up a little. A smoothly cut root would be less likely to cause problems than a torn one. Besides that, there's not much you can do but hope that the tree will overcome the damage.

If it's a big tree, don't worry; it will probably be fine. If it's a small tree, don't worry; there's not much you can do anyway.

thank you brandon

I have a different kind of magnolia root question. I planted a Leonard Messel (northern, small species) magnolia in spring, Just now put a three-foot-diameter, 4"-deep plastic edging around it. This action didn't disturb the magnolia roots yet.

However, I've had second thoughts. Given the shallow-rooting characteristic of magnolias, might even a 4" deep plastic barrier hurt the magnolia eventually? (I gather that the root system will eventually be 5 feet or more in diameter at maturity. ) Will the roots just route themselves under the edging, or will the edging block root growth? (NOTE: to further complicate this question, note that when planting the magnolia I further mounded it perhaps 4" above the surrounding soil level, because I live in a clay soil area. Therefore, some of the roots are already a bit high).

I live in Torrance California and the damage the Magnolia Grandiflora has done to my driveway and yard is big. The pic of the dirt and roots exposed were taken after I removed all the grass when I discovered they were there