Does palmroots spread horizontally even if blocked at the Surface

[Palmfarmer]

Lets say I plant a palm in a small hole in the sidewalk. Its all covered with a few inches of concrete. However there is plenty of room to grow underneath the concrete. Will the roots go down then spread out horizontally once under the concrete? Or will the roots just go straight down in this scenerio? 

Edited November 15, 2023 by Palmfarmer

[SeanK]

I believe that the roots will follow moisture. So if there is moisture somewhere under the sidewalk, the roots will follow it. Most sidewalks are next to roads, so I expect large plants to struggle in these sitings.

[Palmfarmer]

1 hour ago, SeanK said:

I believe that the roots will follow moisture. So if there is moisture somewhere under the sidewalk, the roots will follow it. Most sidewalks are next to roads, so I expect large plants to struggle in these sitings.

There is tons of palms here planted in holes about the size of their trunks that do well. 

I will try to explain it better. If you plant the palm in a small hole. Around it there is a few inches thick concrete or asphalt. However beneth that there is plenty of soil in all directions. Obviously the palm can't root into concrete so it will send its roots vertically down. I am wondering if the roots will start to spread horizontally once the roots go below the concrete/asphalt or whatever groundcover that surrounds it. 

[Silas_Sancona]

 

37 minutes ago, Palmfarmer said:

There is tons of palms here planted in holes about the size of their trunks that do well. 

I will try to explain it better. If you plant the palm in a small hole. Around it there is a few inches thick concrete or asphalt. However beneth that there is plenty of soil in all directions. Obviously the palm can't root into concrete so it will send its roots vertically down. I am wondering if the roots will start to spread horizontally once the roots go below the concrete/asphalt or whatever groundcover that surrounds it. 

If there is soil beneath it, yes, the roots should fan out under that " man made "  " rock "..

A through study of pictures of various palms in habitat shows that yes, -some at least- can squeeze themselves into ..and through... very small cracks in rocks ..or sidewalks ( Washingtonia anyone ? ) ..even on near vertical -oriented cliff faces  w/ out issue.

They Might not look as great compared to specimens growing where there is more space to spread out ...without some sort of tough to get through boundary in their way, but they survive none the less.

[Palmfarmer]

5 minutes ago, Silas_Sancona said:

 

If there is soil beneath it, yes, the roots should fan out under that " man made "  " rock "..

A through study of pictures of various palms in habitat shows that yes, -some at least- can squeeze themselves into ..and through... very small cracks in rocks ..or sidewalks ( Washingtonia anyone ? ) ..even on near vertical -oriented cliff faces  w/ out issue.

They Might not look as great compared to specimens growing where there is more space to spread out ...without some sort of tough to get through boundary in their way, but they survive none the less.

Thanks yeah the Washies can be stubborn haha. Seen them grow in asphalt cracks here. 

There is a Royal close to my house where the trunk has expanded over the original planting hole. It does well for being neglected.

[Silas_Sancona]

2 minutes ago, Palmfarmer said:

Thanks yeah the Washies can be stubborn haha. Seen them grow in asphalt cracks here. 

There is a Royal close to my house where the trunk has expanded over the original planting hole. It does well for being neglected.

Have noted plenty of pictures of various palms growing in some really small ( for my preference anyway )  sidewalk cutouts down there..

Not all may look as great as they could, and a big palm like a Royal ..or Coconut looks a bit silly being stuffed into such a small space ...but, most do continue growing, for how ever long they survive anyway.

Washingtonia will sprout ..and sometimes continue growing.. in rain gutters, so, where there's a will, ..there can be a way. 

[SeanK]

29 minutes ago, Silas_Sancona said:

 

If there is soil beneath it, yes, the roots should fan out under that " man made "  " rock "..

A through study of pictures of various palms in habitat shows that yes, -some at least- can squeeze themselves into ..and through... very small cracks in rocks ..or sidewalks ( Washingtonia anyone ? ) ..even on near vertical -oriented cliff faces  w/ out issue.

They Might not look as great compared to specimens growing where there is more space to spread out ...without some sort of tough to get through boundary in their way, but they survive none the less.

I recommend you start with a plan. Layout on paper what you want to do. Consider architectural structures and background plants. Do all this prior to buy plants and digging holes.

[flplantguy]

There is a sabal growing here in a parking lot with nothing but asphalt for hundreds of feet in any direction.  It's sloped and drains off too so it only gets what it can reach from underneath the asphalt.  It came up on its own in a crack next to a post between curbing blocks, so no one ran it over and it's a few feet tall now.

[Silas_Sancona]

17 minutes ago, SeanK said:

I recommend you start with a plan. Layout on paper what you want to do. Consider architectural structures and background plants. Do all this prior to buy plants and digging holes.

  

[Jim in Los Altos]

Two years ago I demolished my fiberglass over concrete pool that had been converted to a koi pond. As you can see in the photos of an area of the fiberglass cut out, roots from the two Archontophonix cunninghamiana 30 feet away and several feet below the surface, are very evident. Further removal of the pool bottom revealed many more roots that originated from those two palms. Those roots grew under the concrete and stone patio, down the sides of the pool and under the entire pool. The pool was water tight with no leaks and most of the roots were sandwiched between the concrete and fiberglass and quite dry but otherwise healthy looking.  
 

Edited November 15, 2023 by Jim in Los Altos

[Ben F.]

I was wondering the same thing while driving around urban areas with palms in San Diego. So I’m curious how do they get fertilized? If the palm is big and benefits from fertilizer, then usually apply x amount per 1,000 feet of canopy.. so If there is a big canopy, but isn’t much ground, how does one add the right amount of fertilizer? I’m curious because even on my lot I’ve got a few palms near the driveway and backyard patio that don’t have as much dirt space, but still have a big diameter, both in trunk and canopy. 

[Looking Glass]

When digging out the center planter area when we first moved in, I cut through several healthy palm roots.   The nearest palms were 35 feet away.  I agree that as long as there is some moisture, they will travel along it, seeking out more nutrition.  Under sidewalk and driveways sometimes.  Roots extend way past the drip line, when they can…. Sometimes further out than the hight of the mature palm.