Buckthorn and Honeysuckle herbicide questions

giantslug(4b/5 SW Minnesota)November 10, 2008

I have been cutting and and painting the stumps of Common Buckthorn this fall with Garlon 4 in mineral oil (1 part G4 to 3 parts oil). I am wondering how long into winter can I do this and still have it be effective? Will it work even after the soil is frozen? Also, will Garlon 4 in oil work on shrub honeysuckles (Tartarian and Morrow)? I have found conflicting information on this, some sites I have read say Garlon is not effective on honeysuckle and others say it is.

Comments on your experience with killing buckthorn and shrub honeysuckles would be nice too.


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dandy_line(3B (Brainerd, Mn))

Hi. I've been waging war on Buckthorn here in Meeker county for 5 years now. My 2 1/2 acres was totally overrun with the stuff. My strategy is to spray new green growth with high concentration of 2-4-d(~= 2%). This is only done in early Spring when new growth is present. Cutting large plants one year results in lots of suckers the next year which are then doused with 2-4-d. This mostly kills it. About 10% will need another dose the next year. This is the best way I've found to eradicate huge numbers of the things. Spraying in early Spring also saves the natives growing nearby as they green up later.

    Bookmark   November 18, 2008 at 11:57PM
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I've been using Garlon 4 (1 part to 3 parts diesel or bark oil) on buckthorn cut stumps (in MN) for 10 + years. You can treat all through the winter (when I do most of my cutting) with equally good results. It also works well on Tartarian honeysuckle. I've even killed buckthorn this way in spring when the sap flow is supposed to inhibit kill: it still killed for me, but I have a lot more experience in the cold months.

    Bookmark   November 24, 2008 at 8:56PM
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jpal(Boson, Zone 6)

The snow has finally melted here in New England and I'd like to experiment with doing bark treatments on buckthorn. I have a couple of questions I hope someone might answer.

I'm hoping my costs down for this experiment period. (I don't like the idea of using 2,4 D as it sounds rather hazardous.) I haven't found another formula of Triclopyr ester labeled for this use other than Garlon 4, is there one? Maybe something cheaper? If not, is there a place where one might purchase a smaller quantity than 2.5 gallons at 300 plus dollars?

I'd like to not use diesel so I don't piss off some folks around here. Where does one get mineral oil in sprayable quantities? All I've found so far is pints for laxative use :-) Is bark oil available in smallish quantities anywhere?

I'm eagerly looking forward to trying a different technique other than the Weed Wrench attack on the buckthorn. Thanks very much for your assistance, and be assured this information will get quietly spread around the Boston area.

    Bookmark   March 13, 2009 at 2:12AM
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giantslug(4b/5 SW Minnesota)

I found light mineral oil (for livestock use) in one gallon quantities at my local farm/ag supply store. Bark Oil Blue is another diluent that may be available at farm supply stores or ag co-op stores. I found a source for generic Garlon 4 online in one gallon quantities, the link is at the bottom of my post. Pathfinder II herbicide is also less expensive than Garlon 4, it is a pre-mixed triclopyr ester herbicide available in 2.5 gallon quantities. I don't know if you can get it in MA though.
I would be cautious about applying herbicide in the spring, it may not be as effective as applying it in fall and winter.

Here is a link that might be useful: Triclopyr herbicide

    Bookmark   March 22, 2009 at 2:15PM
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My friend who owns a native landscaping business uses 100 percent roundup on buckthorn and paints it on stumps all winter long. He also said you can paint it at 100 percent on the bark at any time and it will absorb the roundup and die.

    Bookmark   March 28, 2009 at 5:14PM
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giantslug(4b/5 SW Minnesota)

Roundup is a brand name. There are products with different chemicals and concentrations under the name Roundup. Glyphosate is the main chemical in most Roundup herbicides. My neighbor has used Roundup RTU (2 percent Glyphosate I think) on cut Buckthorn stumps last year and it was almost totally ineffective. I have read that 20-50 percent Glyphosate concentration should work on Buckthorn. Also, if you are looking for Glyphosate, there are many generic brands that are much cheaper than Roundup.

    Bookmark   March 28, 2009 at 11:19PM
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There are many ways according to this thread. A local Extension officer said on public tv the other day that you can cut, wait for the sprouts, then hit them with Glyphosate 2% on the leaves.

I have 6 nasty acres of the stuff. I have cleared 3 1/2 so far, but the stumps are getting hidden and are hard to get at. I dont want to recut just to apply the Glyphosate. So I guess I will try spraying the sprouts that come up in the fall and see what happens.

Any thoughts?

    Bookmark   June 8, 2009 at 4:16PM
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brandon7 TN_zone(7)

"My friend who owns a native landscaping business ... said you can paint it at 100 percent on the bark at any time and it will absorb the roundup and die."

While I have never tried this, I really doubt it would work even with the Pro strength stuff (homeowner concentrations definitely don't work this way). There is no mechanism to carry the chemical from the bark to other parts of the tree. Maybe enough of the Pro strength stuff would find cracks to enter and, because of it's strength, could be effective at times, but it certainly doesn't sound reliable to me. I'd have to see it to believe it.

    Bookmark   June 9, 2009 at 9:30AM
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I have been using element 4 a generic version of Garlon. I have been using it for several years. You can mix it with mineral oil, diesel fuel or bark oil blue. Just spray around the bottom 3 inches or so of the plant and it will kill it without cutting. It works best sept-march. You can also mix 8 oz with a gallon of water and spray it on the leaves may-aug. but it will also kill any tree if u get it on the leaves.

    Bookmark   May 29, 2013 at 8:06PM
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We are the newish owners of 13.8 acres that has been overrun with buckthorn for many years; some of them are big enough that we're cutting them up for firewood!

I pull ones small enough to do so, and cut off & treat the stumps of the rest ... but it feels like a drop in the bucket. For those of you with larger lots, do you focus your time cutting down the larger ones so they don't seed first, then move on to smaller ones, or ??

    Bookmark   June 3, 2013 at 7:01PM
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madtripper(5/6 Guelph)

1) Spraying Glyphosate on leaves of buckthorn will not kill them. It does cripple the new leaf growth, but after a couple of years they will regrow normally.
2) I would not use 24d. Why spray when you can cut and paint - much more environmentally friendly and safer for you.
3) Saying that you use a certain % of Roundup does not help the reader. Roundup is available in a number of formulations (not counting the competitors) and these formulas have different strengths. the very dilute formulation that is ready for spraying is too dilute.
4) I can't comment on using glyphosate in winter, but it seems to me that this would not work once the tree has lost it's leaves. At that point it has gone dormant. I would recommend doing this in fall, up to leaf fall.
5) The strategy for a large infestation--mine is 4 acres--is to start with berry producing plants. This will be larger female plants. Berries are reported to be viable in the ground for 7 years. the sooner to stop having berries the sooner you will get rid of the Buckthorn.

Once berry producers are gone, get rid of all large plants. You can also go after very small plants. I find that if the ground is wet, you can easily pull plants up to about 2 feet tall. As they get larger, the roots become too strong for hand pulling.

For 3-4 ft plants, I usually wait until they are 5 feet tall - easier to handle then. Cut and paint with glyphosate in fall.

You can leave cut wood on the ground. It gets brittle in one year and rots fairly quickly. I find that it does not make good firewood.

Here is a link that might be useful: Garden Myths

    Bookmark   April 10, 2014 at 9:20PM
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One of the generic Garlon-style herbicides is "Tahoe 4E". I'm sure there are many more.

Cut/treat works well, as does basal bark. Both of these methods use much less active ingredient than foliar spraying, although that method too has its place, particularly in fall after native and desirable plants have gone dormant and are thus, no longer vulnerable to any overspray that might occur. One just needs to be observant as to what's growing on the ground, etc.

One seldom-discussed aspect of this war on buckthorn and other non-native invasive shrubs is the idea of after-planting with shade-tolerant and vigorous native shrubs, in order to depress recolonization by the buckthorn/Tatarian honeysuckle, etc. And the pre-eminent plant that I'm aware of for this purpose is the native elderberry. Shade-tolerant and quite vigorous, this plant also produces lots of bird-attracting berries, all of which will help in the battle.


    Bookmark   April 14, 2014 at 2:23PM
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Anyone know the mix rate for 61% triclopyr 4e with water (for spot spray)? One site said 6oz per gallon of water, but I tried that and it looked like milk, way too strong I think. I'm wondering if about 3oz per gallon would work?

    Bookmark   April 16, 2014 at 3:50PM
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Hi 'bama. I'd go with that very rate as specified. Unless you mean it's so thick it won't spray out decently, that is. I don't happen to have a label in front of me, but what you've reported sounds right on to me.


    Bookmark   April 21, 2014 at 11:51AM
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