THISTLE in BUFFER ZONE - and TREE ROOTS SURFACING

Asked May 3, 2016, 3:19 PM EDT

1. Live next to a pond buffer zone in the Lakes of Blaine - no one maintains it -supposedly the City is responsible but I have been told no money or workers to do so - anyway There is tall thistle in the buffer zone and this is the first year in 10 that it has crept into the grass/lawn area - it has traveled up to 3 feet in this spring. Is there an environmental safe way to get rid of the new plants (ie vinegar maybe) and is thistle a good buffer zone plant - ? 2. We also have approx 10 year old maple and river birch trees that the roots have now surfaced and traveled under landscape rock and headed to under sidewalk / also river birch roots have surfaced and are close to the foundation of our units - we have no basements - if the roots make contact should I assume there will be damage and is there anything to do about it - I have read you can cut and paint the roots - but does the cut portion keep growing to the house foundation - - I hope I am clear - 3. Also, the landscape co. for our Association insists on piling on this red shredded mulch each spring. Then when the lawnmowers, blowers and weed trimmers come by the mulch is blown all over as far as 8 feet away. If it is not raked up it seems to get imbedded in the ground and creates a bare space with no grass. I have been researching on line and I don't know if this is right but it seems like no mulch is really needed, better to just leave it as natural plus I would think it is quite expensive for such a large area of homes. It is probably at lease 6 inches high. on top of mounded black dirt - I see no use for it - weeds still grow in it etc. So I am looking for confirmation that the trees don't benefit from mulch so I can present this information to the Association and also the solutions for the roots and thistle. Thank you so much.

Anoka County Minnesota landscape

3 Responses

Hi and thanks for contacting AaE.

I'm not sure what kinds of thistles you have, but some of them are very invasive and very difficult to control. These links take you to the DNR's sites:
http://www.dnr.state.mn.us/invasives/terrestrialplants/yellowstarthistle.html
http://www.dnr.state.mn.us/invasives/terrestrialplants/herbaceous/bullthistle.html
http://www.dnr.state.mn.us/invasives/terrestrialplants/herbaceous/canadathistle.html
If these plants are bordering a lake you should contact the DNR to see if they can offer advise or help in eliminating them.

Control methods and options are listed in the sites. Vinegar is not an effective herbicide, and will harm surrounding plants.

The tree roots will not harm your foundation. Some trees have surface roots that make mowing difficult, and walking even more so. However cutting these roots will harm the tree and can even make it unstable.

The mulch is beneficial to the trees, and they will do much better if mulched. The mulch can and should be contained with a very short barrier in order to prevent it from washing or blowing around, but it sounds like the folks who mow these lawns are very careless. Your association should make it clear that mowing into the mulch is not acceptable, and landscapers need to repair any lawn damage caused by their actions. I hope this is helpful. Please contact AaE again if you have further questions.


Thank you for your response - - I have now confirmed the invasive plant coming into the lawn from buffer zone is Raspberry - not Thistle - - So any suggestions on what to do with the Raspberry - ? Every day it creeps in more - now some places 4 ft. Also regarding the tree roots when the roots grow under the sidewalk won't that break the concrete up and what happens when the roots of the tree hit/touch the concrete block - will they grow under? I know someone who had an old limestone basement and the roots came in right through the wall. Thank you.

Good afternoon, I am glad you have been able to get a clear identification of the invasive plant. To eradicate the wild bramble you will have to use a stronger herbicide that contains an active ingredient of either glyphosate or triclopyr. These are contact herbicides- whatever plant material they touch will die. Since your problem seems a bit severe you may have to make multiple applications. The label contains information on the rate to use and how long one must wait before reapplying. As for the roots, river birch are shallow rooted trees. Seldomly do they cause a problem with a homes foundation. But they are prone to come to the surface in search for water. It will not be surprising if they or the maples roots do shift your sidewalk slightly. However, as the previous Extension specialist mentioned cutting a trees roots could cause more damage than good. If you do decide to root prune, I would not remove more than 25% of the total root mass. For a reference of the amount of roots a tree has, roots generally fill the entire area under the canopy. Consider this link before taking action (https://hort.purdue.edu/ext/treeroots.html). Though a little dated, the information is still relevant! Please let us know if you have any further questions.