dirt and tree question

[cj]

I would like to built a small raised flowerbed (knee high) around the base of a mature oak tree. My question is having the dirt in contact with the tree bark going to harm the tree?

Thanks, CJ

[Ken]

You may want to check with a college extension service that deals with such questions, but I have been told that if you raise the dirt level at the trunk of an oak tree you stand to kill the tree. I have seen this happen locally, so I would make sure I knew what the story was before doing so.

[Frank]

On This Old House they showed the problem with too much mulch around the tree caused root growth into the mulch that harmed the tree.

[dpb]

Won't do it any good, certainly.

Unless the width of this is going to be very small, it's likely to also cause distress from the additional ground/dirt over the established root level. You can probably get away w/ something like a foot or so wide if you also build a retaining wall on the inside as well as outer, but I'd still advise against it.

[Dan Espen]

Yes it will harm the tree.

Definitely not recommended.

Usually flowerbeds need full sun.

[micky]

Answer to opposite question: (Sorry) In 1956, after my father died, some gardener told my mother there was too much dirt around our oak tree BELOW the surface of the lawn. And she should pay him to dig a doughnut around the tree, about 4 or 6 feet total diameter, 14 or 18" deep. (I don't think I ever knew what was supposed to happen if she didn't.) I was 9 and couldn't do the job, I guess (though it would have been good for me to try.)

My mother had never heard of such a thing, and 50 years later, I don't think I've everf seen another tree like that anywhere else, and she was afraid she was being cheated.

But she did it. 50 years later, the hole is still there, but smaller because the tree trunk is bigger and leaves must have follen into the hole. and the oak tree is still doing great. It's in front of all the windows on the second floor (two bedrooms) and taller than the pitched roof iirc.

Of course it's an oak tree and theyr'e supposed to live a long time.

Was she cheated?

Here is a picture of the tree from above Enter 41.019681,-80.341701 in google maps search field at

It's the 2nd house left of the house with the white roof and the bright white driveway. It's the house with the big tree in the front yard.

Wow, now the tree reaches almost to the sidewalk that parallels the street. And its over the front half of the house. No street view on this street.

[micky]

Thanks. So it doesn't mean a thing that my triee is maybe 83 years old. So I still wonder, Was there any point in digging that hole ar0ound the tree?

BTW, the 329+ year tree is showing its age, with empty sections. My tree is as hearty as a young woman, with a complete canopy with no holes, from above, and last time I was there about 15 years ago, from below.

[dpb]

On 2/18/2013 9:14 PM, micky wrote: ...

Depending on variety, it may still be just a youngster. Average for undisturbed white oak is 300 yr or so w/ maximums approaching 600. Northern red oaks, post oak, chestnut oak are generally around 400 yr for max longevity and many of the other typically slightly faster growing are closer to 200 max. There are something approaching 200 species of oaks in North America alone, so while all are relatively long-lived, it's hard to say much more about any one, particularly not knowing what variety it might be. Guessing from the location it might be a pin oak, that's one of the shorter, 200 max kinda' guys.

Would have to know/see what it actually was like before, but I seriously doubt it had any real effect one way or the other at that time and location of the trench wrt the tree.

...

[Vic Smith]

My wife built a 4" high flower bed around the old crabapple tree. Used concrete blocks. Wasn't any bark to speak of that low on the tree. But the flowers didn't do well, and after about 5 years the tree roots started growing up, making the blocks uneven and askew. We didn't try it with any other trees after that. That's all I know.

[HeyBub]

Think.

The reason you've never seen such a configuration is because trees so arranged died.

[Norminn]

Whenever I've read articles about planting trees, it is always stressed that they be planted at same soil level as in the pot. Many articles about landscaping mention that soil and mulch should not contact the trunk, as it encourages disease and insect infestation. If I had a large oak and enough space (and the right climate), I'd plant rhododendrons and azaleas...I did that when I lived in Florida and they were gorgeous. Rho. and az. are also good place to put leaves that are shed....they make good mulch for acid loving plants.

[George]

Yes, same is true for piling a large amount of mulch around the tree.

[trader4]

The volcano mulch pile is the latest trend here in NJ. Twenty years ago, maybe even ten years ago, you never saw it. But with all the city folks moving here and the clueless landscapers, now it's a common occurence. Actually, maybe the landscapers aren't that clueless. They get to sell more mulch that way and if the tree dies in 10 years, they get paid to take care of that too.

Another driving factor for the mulch piles are lazy builders and landscapers. I've seen new construction where instead of digging a full hole, they dig half a hole, set the tree with half or a third of the root ball above the soil, then cover it with a mulch volcano.

[Moe DeLoughan]

It is never a good idea to raise the soil level around an established tree. It will cause harm to the tree.

A smarter approach is to remove a circle of grass around the tree, put down landscape cloth and a layer of mulch (don't pile the mulch against the trunk). Edge the mulch bed with plastic or brick edging, then arrange a few pots on the mulch around the tree. Choose plants that will do well in the lower light levels underneath the tree's canopy. An alternate approach is to dig a few holes in the ground through the landscape cloth and place pots into the holes. But frankly, just having the pots on the surface is less work, especially since the pots can be shifted easily to show off a pot whose plant is doing especially well.

This approach won't harm the tree, and you won't have tree roots intruding on the ornamental plants.

[DerbyDad03]

See here...

[Dan Espen]

The image shows a doughnut built around the tree. A dry well in the middle with drainage under the filled part.

I think the dry well part will need frequent cleaning out and tree roots will still grow up through the rocks into the soil.

Still little light under a tree and not a good idea.

[Norminn]

That setup might interfere with nutrients/water getting to the roots. Some trees have shallow root systems and I think they would be more bothered.

[trader4]

I think that's a valid point. I would think most of the nutrients are in the upper part of the soil. After you go down 18" or

2ft I wonder how much there is?

[Moe DeLoughan]

There's no guarantee of success even with this level of effort. This method was used in a small development in my area, where the city permitted the developer to grade the plat and build houses on the site, provided they protected the existing trees. They used this method, but the trees died within a decade anyway.

Ironically, the front yards of several of the homes still have the dry wells in place, even though there's nothing inside. Dunno why they don't just dump some dirt in, sod over it, and be done with it.

[Dan Espen]

Not surprised.

Can't think of any old trees I've ever seen living in a hole.