Can I build an island around a tree?

[rtimgray]

I have a plan to expand an existing pond by raising the levee on one end of it. This will end up raising the water level by about 3 or 4 feet. This will should cause more area to flood, thus making the pond bigger.

There are several trees in the area that will be flooded, but most of them are nothing that I would want to keep. There is, however, a large oak that I wish I could keep. It is about 30" diameter trunk, probably 70 or 80 feet tall. So here's the crux of the question:

Could I build an island around the tree and leave it out in the pond? If I did nothing, the water level (at it's highest) would be about 3 feet up the trunk of the tree. I had wondered about building a bermed island that would be maybe about four or five feet tall (relative to the bottom of the tree, which is existing grade) all around the tree (a radius of 20' or so). Then I thought I might build a retaining wall around the trunk of the tree down to existing grade level. Essentially, the island would be a donut around the tree trunk. Would this allow the tree to live, or would it just die slower? Do you think the water would seep through and fill up the cavity between the retaining wall and the tree trunk (thus defeating the purpose of the donut island)? Has anybody ever done anything like this before? Does anyone have any alternate ideas or suggestions?

Thanks for the help.

 

[FrogLick]

Sounds like your efforts to save that mighty oak are very ambitious but I believe that it would ultimately be drowned. To even have a chance of success your "island" berms & retaining wall would have to be larger than the diameter of the tree's canopy; consider the canopy as the currently active root system and plan for future growth. Seems to me that this plan would require significant earthworks and expense and you'd end up with an oak in a well rather than on an island. If nothing else I don't see how the ground water level under tree wouldn't significantly rise leaving it with wet feet.

An oak of this size is certainly valuable and worth saving if you can. Have you considered having it moved instead? There is specialized equipment and methods for moving a tree of this size so it would not be a DIY project. Don't know how much it would cost but it might be worth getting an estimate. With any luck it might not be much more than what you'd spend on your island plan and have a better chance of saving the tree. Of course you could contact a logger and sell it for lumber before raising the lake level but that wouldn't accomplish your goal.

 

[rtimgray]

Moving it is not really an option (just because even if it can be done, I won't spend that kind of money on it.). The construction of an island around the tree would be relatively cheap. I would be using my tractors and dozer to do the earthwork, and the island would be constructed of local dirt (from the area of land to be impounded, thus accomplishing both the construction of the island and the deepening of the pond).

I'm afraid that the water would fill up the donut hole of the island. Does covering the tree roots with water effectively "drown" the tree? What if the island had no retaining ring around the tree and I just filled it all with dirt? Will burying the roots an addition 5 feet also kill the tree? Again, I'm assuming it would, but I've never done it or seen it done.

Thanks for the input.

 

[AlanB]

I think the question will be a matter of time frame in my opinion.

If you raise the dirt too high up on a tree, it will die, now exactly how high is too high is up for argument.

Do you have time to raise the dirt around the tree say 3" every month? (I would think that would be quick for the tree, and slow for your building process but it might be a reasonable compromise.

I cannot picture the tree living 3' under water.

I think if you built retaining walls around it, the water would just slowly work through and fill, not to mention rain water etc. I cannot picture pumping out etc. in this circumstance.

I think if you just direct buried it the additional 5 feet it would be dead.

Good luck, be interesting to see how this shakes out.

 

[kthompson]

I feel your pain on the oak tree as we have been for the last few months being doing very much what you are wanting to do. Based upon what I have seen and been told you will kill the tree, probably either way. Some oaks will take wetter feet than others so I suggest you see if you can find out for the exact oak type you have. It has been about 7 years ago that I built up the dirt around some hardwoods about that amount but ONLY on ONE side. Some were oaks, and to this day they have shown no harm. The other side is to be filled in one day due to the pond work and I think it has been long enough they have adjusted and will make it.

 

[Maxfli]

Can't say I am any kind of expert on the subject, but I have a lot of old oaks on my property and have don some research. When we built the house we set the foundation back 25' from any of the oaks which mostly got us to the outer edges of the drip line of the tree, so you are close with idea of radius of 20'. I think it would be difficult to hold back the water in any meaningful permanent way, and other reading I have done would suggest any type of top dressing over the tree's roots system would kill the tree. I do a a wetlands area and 1 lone oak is struggling to survive in that wet condition. I think oaks (at least Burr Oak) can withstand a wet footing. My view is everything you are suggesting here would eventually kill the tree. The tap root on a tree that size goes very deep, moving it would certianly kill it.

 

[ToadHill]

It depends on what kind of Oak it is. White Oak is sometimes called swamp oak and will live in areas with soggy feet. Most other Oaks do not like wet feet and will probably not survive.

 

[rtimgray]

I'm not planning on raising the levee this year; probably next August, so I've got about a year. I could start building the island around it in lifts, raising it 3" or 6" at a time each month. I'm gonna continue to research it, but I will probably just build the island around it and raise the pond. The tree can stand there till it dies, then I'll just have to go cut it down and pull it out of the pond. There is nothing that will be in danger if it falls after the pond is impounded (unless you happen to be under it when it goes - and that's just more unlucky than I hope to ever be.)

 

[Treemonkey1000]

I am not much of an expert on oaks mayself. My concern would be if you get some big windstorms like we do around here in Seattle. With it being plopped in the middle of a soggy area like that it might be liable to blow over. I see that fairly often when their roots get wet and a large tree they catch the wind pretty well. Now being weighted down with extra soil at the base might help. There again not being an expert I think covering up the trunk much above the root ball could cause rot or allow pest to drill in. That's if there are pest that like oak.

 

[dirtworksequip]

Just raise your pond and forget about trying to save the tree. Sounds like no matter what you try the tree will die. Just leave it there even after it's dead it will still provide habitat for some type of wildlife.

Sincerely, Dirt

Note: Locust tree in about 2 feet of water at far end of pond.