Landscaping under mature little leaf linden trees

Hello!

I'm a long time watcher on Dave's Garden, but now that I finally have a garden of my own, I need some help! We just bought a lovely little property with 4 mature little leaf lindens (Tilia cordata) on it. I was hoping for input on landscaping under it.

Description: Our living room will have a very large bay window looking out on these lovely trees and I would like to add some interest there without hurting the trees. The trees are on a slope so that they are about a foot and half (30 cm ?) above the rest of the yard. Right now, there is just struggling grass and a lot of moss under the trees which are about 60 ft tall (20 m). On the other side of the trees, there is a road about 15 feet (5m) from them (and lots of bumps in it from their roots pushing it up!).

I was hoping to do a raised bed under the trees that would be a little lower than the height of the root buttress ( about a foot/ 20cm deep) and put in some shade loving plants and maybe an interesting small tree or 2. However, when I was researching, I found that lindens can be particularly sensitive to modifications in the soil around their roots and even a raised bed could kill them (and many trees for that matter). I definitely don't want to hurt them, and since we will be adding on a small addition about 10 feet (4m) beyond their dripline, I'm worried that they will already be stressed. So any landscaping would be a few years down the line :( We will be putting in a rain collection tank and a drip irrigation system, so I hope that will help the trees (and anything we might plant under them) deal with water as well as fencing to protect the roots near the dripline during construction.

Questions: Does anyone have experience landscaping under little leaf lindens or other root-sensitive trees? Could I add a couple of inches of dirt per year to build up the spot and then plant bulbs and small plants that shouldn't disturb the root system too much? Should I just try to do a container garden underneath? Or maybe a few small raised beds at a time? Am I worried about nothing? Any ideas about how long I should wait before deciding if they are stressed?

Any first hand experience or tips would be greatly appreciated since I have not been able to find tree specialists here in France and the "expert" landscapers I talk to don't seem too worried about the trees...

Thanks!

From searching around the web, it seems that ferns, hostas, lily of the valley, lungwort, wood poppy and columbines tend to do best under T cordata. As for adding soil, care must be taken to not smother the existing roots. A couple sites I viewed recommended making "plant pockets"....raised areas scattered under the trees (adding a few inches of soil to accommodate the underplantings, but not adding heavy layers over the entire area.) Sort of a series of miniature raised beds, with a couple inches of mulch over the entire area. This would allow the sensitive tree roots to "breathe" and still allow enough soil for underplantings without having to dig too deeply.

Unfortunately, T cordata does not grow well where I am. here is some general info for you.

http://hort.ufl.edu/database/documents/pdf/tree_fact_sheets/tilcora.pdf
Info on tree roots

http://www.uwsp.edu/forestry/Documents/hauer/Talks/One_Root_Two_Root.pdf

http://joa.isa-arbor.com/request.asp?JournalID=1&ArticleID=2447&Type=2

I would never raise the soil level around a tree, not even a little, not even over a long period of time.
Not if I value the trees, anyway.
When I plant under a very sensitive tree it is purely by digging a small hole between roots and wedging a plant in there. If I dig and hit a root I scoot over and try again. So no meticulously measured grids or spacing- you get what you get.

But to be honest, the roots of a large mature tree are such water hogs that it can be a challenge to keep smaller plants adequately hydrated. Since I figured this out for myself (duh!) I have not been trying to plant nearly as close to the trees as I did previously. I don't even start planting things until around ten feet or so out. And even then many trees develop a mat of very fine feeder roots very near the surface that go out forever and they can be murder to try and dig into. If I can't dig a planting pocket with a small garden trowel I don't plant there.
And I certainly would not turn my husband loose with a shovel- IMO that's just asking for too much damage.

I should add that I am not familiar with Linden trees- my large trees are oaks and hickories and your trees moisture needs may be different.
I am just speaking in general.

60 foot tall trees have been growing with their roots used to that level of soil for too long for you to alter it.
Tillia are shallow rooted, and these are used to frequent rains, or irrigation from the attempts to grow a lawn there.
I would get rid of the grass, and just mulch with a coarse material that will still let the roots breathe.
If you really must have more plants under the trees, then start with the smallest plants you can (like the ultimate small plant: Seeds) and tuck them in wherever the roots allow. Many plants that are originally from a forest floor are good choices because they thrive in the dappled light and can usually handle some competition from the roots.
Try a few each of several things, and whatever makes it, plant more of those.

Away from the trees would be fine to try adding plants. Even then you might still find some roots, so the idea of using a small tool, and move to a new spot is the best way to plant.

Other things that might add interest without harming the trees:
Boulders, statuary, a fountain, other garden accessories.

Good to protect the root zone when you are having work done on the house. If there will be root damage (roots removed to make room for the foundation) make sure the upper part of the trees get pruned to match the amount of roots lost.

Thank you so much for the feedback! You all have pretty much confirmed my "fears" about landscaping under these beautiful trees. I'm just worried about 25 feet of window looking out on a sad mulched lawn under the trees. The ground is definitely dry during the summer but I am planning on putting in a rain collector and drip irrigation so I was hoping to help with that. I guess I might try some "miniature" raised beds just beyond the drip line, which will put us practially up against our extension... Or find some creative decorations!

@Diana_K: We were planning on having the trees pruned at the end of next winter, but then I was worried that the combination of disturbed roots and pruning might really stress the trees, so I was thinking of waiting 3 years to let the tree rest. Our neighbors complain constantly about the leaves and that they are too tall for a residential neighborhood (the French are definitely not used to big old trees in residential neighborhoods, unfortunately). We were planning on having them trimmed by a third, which was what the trimmer service recommended (but I'm not sure how worried they are about longterm health). What do you think?

I know Tilia have shallow roots that seem to go far beyond their dripline, but I haven't actually started digging in that area so I don't know how big the roots are at this distance. We would definitely not be disturbing a third of their root system, so should be think of a trim that is more proportionate to the disturbance? Or would a big trim like this be ok? Is it too late to wait until the tree's winter rest period or should we trim as soon as we see that we have cut a lot of roots (if that happens).

I have also read that adding phosphates, but not nitrogen, could help the tree recover from root loss. Since I'm an all-organic gardener, I was thinking of putting down bone meal and doing weekly deep soakings to help get the trees through all these changes. Any thoughts?

Merci beaucoup!!

Trim as soon as you see how much root damage has been done. For example, if you start building right away, and cut the roots now, the tree will not make it through all summer with the heavy leaf load and a compromised root system. Prune right away.

If your building does not start until the fall, then it is OK to hold off a bit on the pruning, as long as the tree is dormant. But make sure it is pruned before the spring growth starts. Do not wait several years! The pruned roots are gone, not capable of supporting that much top growth. That top growth needs to be removed.

How it is removed is up to you and the arborist (professional tree person). Perhaps thinning all the tree. Perhaps selectively removing certain branches.

Do not prune to satisfy your neighbor's idea of what trees are. It is an argument you will never win. Keep the discussion between you and the arborist.

If your soil is low in phosphates, fertilizing with a slow release source can help.
Deep, infrequent soaking is best. Do not keep the soil any wetter than the trees are already used to. There are many soil fungi that can attack the roots. When you water you are excluding oxygen from the soil. Trees (all plants) need a balance between oxygen and water. The fungi most often grow when the soil stays too wet, and low in oxygen.
The trees are adapted to fighting whatever fungi are willing to grow in the normal amount of water the trees have been getting. If the normal amount has only been once a month, do not irrigate more often. If the trees are accustomed to weekly water in the heat of the summer, then do that.

Years ago, in the early 80's, I planted a Tilia Cordata, in amended sandy soil, on LI. Around the same time, I underplanted with Epimedium and Galium Odorata, and a dwarf Pieris nearby. I added spring bulbs as well. I also mulched and irrigated. The last time I saw that garden was about 5 years ago, and all were thriving. The ground covers had expanded over all the available area, and the Pieris had matured into a lovely low shrub.

Obviously I wasn't disturbing the tree roots as I planted, since it was new. My point is that all co-existed well together as time went on, so I think if you're careful about interfering with the tree roots as little as possible, and patient, over time you may be able to add quite a lot to the area.

Good luck!

Pam

Many thanks, Diana and Pam!

The construction will actually be a few yards beyond their drip line, so 'I'm hoping not too many roots will be cut. Crossing my fingers!

We did cut down a large Christmas tree that was shading the roots of the trees. I'm hoping mulch will help. We have also been doing lots of garden work during a soggy spring. I'm sure we compacted soil. Yikes! Who knew these gorgeous old trees could be so fragile? Double crossing fingers!

Thanks again, ladies!

Like you, we had a mature Linden tree in our front yard. Initally all that existed was struggling grass, and weeds - nothing else could compete with all the sun and rain and nutrients that this huge but beautiful tree absorbed. Over time, we planted pachysandra, vinca, hostas and daylilies (hemerocallis) in little pockets of soil and let them duke it out. We sold the house, but the new owners (who are by self-admission, not gardeners at all) are able to keep all 4 alive!