I forgot, I also wanted to ask if it was a good idea or sound composting practice to use left over/used container dirt as a layer in the lasagna garden.

Don't know about the container dirt but I don't see why it would hurt. I wouldn't think this would really cause a problem. But I would like to point out you wouldn't want the stuff up against the trunks because it will make the bark soft and allow bugs and fungus to going in and damage the trunk.

The one small problem I would see is that in a few years you will have a lot of roots in that garden bed from those trees. If you can work around that or deal with that I wouldn't see why it would be a problem.

I would try to keep the leaves/mulch away from actually touching the tree trunks. and I want to eventually have this be mostly a perennial garden (maybe some annuals near the edges) but at least where I won't be distrubing the roots too much. I needs/want some privacy through there and it's really hard to mow this part of the lawn, we're trying to cut down on the amount of lawn we have to cut.

Sorry but I would have to agree with the concerns laid out above. The benefit to the tree itself is minimal and the potential for suffocation of the surface roots and trunk damage from pests and moisture rot is pretty high.

To compensate for the smothering, the tree's surface roots quickly invade the bed to get the air that was readily available to before. End result is a bed where not much can grow as the plot is now rootbound.

I don't know if you posted this over on the Trees forum but I think you will find that many arborists discourage the building of beds under/around trees or heavily mulching them, which is basically what a lasagna bed is, for the good of the tree. While a light surface mulch can help conserve moisture for the tree, anything as thick as a lasagna bed would problematic. The most common recommendation I have read is no closer than 6" from the trunk of the tree.

Dave

Here is a link that might be useful: Proper Tree Mulching

you do not want soil in your mulch. You can use it as soil at the bottom but not in the layers. also old container soil can sometimes have salt build up if you are in the west and your water has a salt content. It can also be deficient in nutrients that have been taken by the previous plant.
I agree with dig's not to close to the tree.

There is no reason why you could not do this, as long as you do not make those planting beds really deep, and you can put that potting (container) soil in that mixture. If people can mulch around trees with a 6 inch thick mulch with no harm to the trees you can build a planting bed which would make tending around those trees much easier than trying to mow grass. The area of the drip line of many of the trees I have are mulched, thickly, and have been for years with no harm to the trees.

People DON'T put 6 inch thick mulch around trees without harming them. Putting that mulch around a tree encourages roots to grow around the trunk and eventually girdle it. It also provides homes for rodents that feed on the bark which also can girdle the tree. The results aren't seen for several years since damage done to trees is often not obvious for several years. Your plan doesn't sound harmful to the trees at all, though. The change may stress them, but I think you will eventually be doing them good as the nutrients you are likely to add to the garden will also be good for the tree. You just might find you need to add more than if you weren't under trees.

thank you for the responses. my plan is to build up the mulch slowly through the lasagna method (this is why I'm not trucking in a foot of topsoil and buying yards and yards of tree bark mulch). I kinda figured I'd be mimicking what happens in a forest where the leaves are allowed to fall and mix with dying vegetation (in this case grass clippings) to form nice nutrient rich tposoil and mulch a few inches thick. I will keep the layers thin and gradually add more to build it up over years. I'm not looking to end up with a foot of material added in one season. This will be an "at grade bed". I'm okay with the roots making their way through the compost layers to reach the surface again, as long as I don't have to mow the lawn around them. I do have grass around all of these trees, if it was a barren part of the yard where nothing would grow, I wouldbn't worry about it so much, so the grass needs to be cut here and it's really difficult.

Also, I don't plan to pack the bed full of plants either, just some mums/irises/ferns/hostas, small pereninals that will coexist around the trees.

Be sure to keep the root flare of the tree exposed. Here's a photo of a properly planted tree with root flare showing.

http://hgic.clemson.edu/hottopics/images/2007/12rootflare.jpg

This tree's root flare is covered, which will lead to a less healthy tree, and can ultimately kill the tree

http://www.tlcfortrees.info/images/no%20root%20flare.jpg

Here's a pic of the partially excavated tree, showing the girdling root that was growing just under the soil line.

http://www.tlcfortrees.info/images/root%20girdle.jpg

Here is a link that might be useful: TLC for trees

here's where I want to have the lasagna garden

http://www.shutterfly.com/lightbox/view.sfly?fid=f6806dec29f007fcc9f3edf1ebadc1fb

I will keep the layers away from the tree flare, thanks for the pictures!

Sorry we can't see your photo without joining the host. Your photo should have a HTML code attached to it - a URL that starts with As to building the bed, as we have pointed out, it isn't recommended, indeed strongly discouraged by most tree doctors/authorities on the subject. There are lots of internet articles on the associated problems you can review if you wish. But I suppose if you begin it very gradually and carefully monitor the tree health as you go along you'll be able to see when it begins to harm the tree and can stop at that point.

But I had to smile at this comment:

Also, I don't plan to pack the bed full of plants either, just some mums/irises/ferns/hostas, small pereninals that will coexist around the trees.

Given the expansive nature of hostas, iris, and ferns, it makes me wonder what you would consider a "bed full of plants" if not all that. :^)

Good luck.

Dave

I'll work on getting the picture visable.
I guess I just don't understand how I can see so many flower gardens with large mature trees in them, or large tres surrounded by small mulch piles like 6' in diamter around a 2' diameter trunk) around them and the trees are perfectly fine. I can hardly cut the grass around this tree, yet the I can't kill the grass or I'll be left with a mid pile that my dog would certinly find appleaing during every rain event. I guess I saw this is my best option to be economically and environmentally friendly.

And the plants that I mentioned above are all free/hand-me-downs from relatives and co-workers that I'd have to choose from. I'm not spending any money on anything to put in that bed for a few years at least. and not all of them are going in this bed, as I have 2 other bed to fill in with shade plants too. The mums I got at a wedding (centerpieces), so again, they're free, and they're going in a full sun (southern exposure) area about 25' from the tree, away from the canopy edge.

Craftlady,
I've been following this thread with interest, as I have done a similar lasagna bed this fall around a mountain ash. It is an extension of a lasagna bed I started the year before. Really, by the time I planted in the first bed early in summer, the mulch layer was not very deep at all. It will continue to compost I'm sure. I guess I didn't really make a lasagna bed. It wasn't more than a few inches thick. I used newspaper and shredded leaves and grass clippings; then a thin layer of compost to hold the leaves in place. I've seen this method referred to as sheet composting. I don't intend to alter the soil level near the tree trunk. My intention was to plant a few hostas there, and to not have to mow the grass.
It sure wasn't my intention to kill the tree though. Like you, I'm wondering how others successfully incorporate trees into their flower beds if this is such a bad idea.

At issue seems to be the final planted depth of the tree. If that bed were initially planned and the tree planted at the proper depth so that root flare is visible, no probelem at all. The problem would arise if the bed were formed later by building UP from the initial level with the final result being that the tree is planted too deeply.

Karen

Here is a link that might be useful: What root flare should look like

Trees that get planted in existing beds have no problems. But that is different that trying to incorporate an older, well established tree into a new bed. Many of the beds you see with trees in them have left a band (as wide as the drip diameter of the top) free from cover and then begun the encircling bed.

And trees that you see with mounds of mulch may look healthy now but really aren't.

Craftlady, I think that some trees are much easier to garden underneath than others. Maples are notoriously difficult because they have shallow and aggressive roots. I have a lot of experience with maples, because I have 3 mature species growing in this yard, Acer saccharum (Sugar), Acer saccharinum (SIlver), and Acer platanoides (Norway - this is an invasive species and I've removed 4 out of 5 large trees so far). Not sure which large trees are easier to grow under but Oaks are probably better?

Silver and Norway maples are the worst! Silver maples have large surface roots that aggressively grow in whichever direction the water is located, including gardens and septic systems. Norway maples have allelopathic roots, which means they have a toxin they exude that suppresses the growth of the roots of other plants. As for Sugar maples, their roots are not as aggressive, BUT they are extremely sensitive to root disturbance, compaction, and salt, so I would garden very little if at all under a mature Sugar. And if any construction is planned near a Sugar maple they need a wide berth not to be damaged by heavy equipment.

In your case, I wouldn't worry in the least about putting a lasagne bed under the Silver maple. They are primarily a wetland tree that tolerates seasonal flooding - their roots have a high anaerobic tolerance. You can't smother a Silver maple with a lasagne bed or 6 inches of mulch if they aren't smothered by 2 feet of water! But as other posters pointed out, you will have your hands full dealing with their roots.

I would dig nice big holes and cut back the Silver maples roots to give your new plantings a chance to get established.

You should search for several previous threads on gardening under trees--also Google results.

The silver maple is a real challenge, but things like hostas, bulbs, daylillies, some groundcovers and other things can work. Most success is had with planting in small pockets and with plants that tolerate dry conditions (hostas will do so once established and if not in sun).

What you need to remember about planting under a tree with aggressive surface roots is not just the idea of adding thin layers and using loose organic materials (shredded leaves, grass clippings, fine bark) rather than dirt--although I would not recommend placing 6 inches at once--it's that you won't ever build up significant depth of good "soil" because the tree will extend its root system into what you layer on top of it. So your resulting bed will always tend to be a mat of roots and will not turn into inches of nice loam as will a regular lasagne bed elsewhere. So when you add a layer of mulch, it will be a layer of mulch at first, into which you typically can't plant much, and then a year or so later, the broken down part will be tree root heaven.

Another unintended consequence that you should be prepared to deal with is that weeds will grow better the more you improve the soil surface, and will often grow better than what you want planted, so sometimes you turn a bare-ground, rooty area eyesore into a weed patch eyesore by adding more nutrient material to the surface. Also, the maple whirlies will take root easier.

So, take a look at what part of the bed will be mostly silver maple, versus other, and don't plan on any kind of lush flower garden under the maple.

Another idea to consider is using containers under the trees. Sometimes you can establish a groundcover for unity (tying the trees together) and then nestle in container plantings, both for height, and because by avoiding root competition you can grow a lot of things--shrubs, annuals, perennials--that you could not grow directly in the ground.

For many years I have maintained a 6 to 8 inch thick mulch layer of wood chips around many of my trees and shrubs with no harm to those trees and shrubs and many other people I know do the same with no harm to those trees and shrubs. Other people I know that will not do this have had their trees and shrubs die from lack of soil moisture. It is not inherently bad to put down that much mulch although whether it will work for you may depend on how good your soil is. If your soil is not good and healthy putting that much organic matter on top may create problems.

So, how about laying down the lasagna components while avoiding covering roots? I have a mature magnolia and a really nice-sized Japanese maple, both stuck plumb out there in the middle of the fenced area. They are isolated both visually and in terms of placement from every other element in the garden.

My plan had been to create an elliptoid-shaped bed, with one tree at each end. I figured mulching and planting directly under the trees would be a real challenge -- current thought had been to do what I suggested, and that's lay down layers for the bed but placing nothing on top of surface roots, and placing a relatively limited amount of material wherever it appeared there were roots quite near to the soil surface.

As for planting under the trees, at the moment I haven't a clue, other than perhaps epimediums and maybe my hellebores. But at least the center of the ellipse could be full of stuff, and the trees wouldn't look as if they'd fallen randomly into the garden from outer space.

In addition to the links provided above on mulching trees, there are numerous discussions and a FAQ on this issue over on the Growing Trees forum here, many posted by professional arborists. When in doubt, why not defer to the experts? Better yet, ask your local county extension service.

For additional info see:

Morton Arboretum: Mulching Trees and Shrubs

Delaware Forestry Brochure: Mulching Trees

Univ. of New Hampshire AG Extension: Planting and Mulching Trees and Shrubs

U. of Tenn.: Mulching Your Trees
and Landscapes

Lots of info available out there. ;)

Dave

What I have seen over many years of gardening is that a 2 inch thick layer of mulch is not quite enough to stop "weed" growth and will need the assistance of newspaper or cardboard to suppress those unw3anted plants. A 4 inch thick layer of mulch will do that better but a 6 to 8 inch layer will do that longer and will not harm the tree. A visit to one of the arboretums and a good, close look at the mulch they have down probably will show you that it is closer to the 6 inch level then it is to 4 inches.

If you read the OP's question, it had several components and was not just about mulching a tree, but about creating a "bed" that could be planted in come spring, and implied that the bed would be over the tree roots. So that's what I tried to respond to.

If the "bed" is just a field of mulch that will remain just that, and the planted area is not over or in the tree's root system, then that is maybe a different question. And lynxe's comment could be related, if the mulch is tying the trees and the garden together, not the actual planted bed doing so, but depends on whether the true root system is being avoided or whether someone thinks that only visible roots are the issue, as in, see, I didnt' put anything over the roots.