Using Roundup near conifers

katskan41June 16, 2007

Greetings all. Can anyone tell me how resistant young conifers (3-5 feet tall) are to products like Roundup (glyphosate)? I'd like to get rid of weeds and grass around and near the conifers but am uncertain whether Roundup would harm or even kill them. Most are blue spruces, white spruces, concolor firs, Serbian spruces and Eastern white pines.



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Kats-I'd advise utmost caution to NOT get Roundup on your trees. That doesn't mean you can't apply it to weeds right near your trees, but in my experience, folks who set out with the notion that it's okay to get a "little" Roundup on their landscape plants pretty soon are getting a lot on them. Later, these plants are not doing so well.

I spray Roundup-like products around and near landscape plants all the time. The trick is to be sure to angle the spray nozzle properly to hit your targets and not your trees. We've gone as far as pinning tall growing weeds like quack grass or Canada thistle to the ground with little U-shaped pieces of wire, to get them out from within the landscape plant, and make them suitable targets for the spray.

There's also the "wet glove" technique-putting a chemically resistant glove on your hand followed by a larger cotton work glove. Roundup can be applied to the glove and wiped onto offending plants. Very slow and tedious, but sometimes the only answer.


    Bookmark   June 16, 2007 at 3:59PM
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Embothrium(USDA 8 Sunset 5 WA)

Hold a piece of cardboard up between the sprayer and the plant being protected to shield it. Or cut the top off a plastic jug and put it over the nozzle, to keep the spray from drifting sideways.

    Bookmark   June 16, 2007 at 4:50PM
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If you have not used chemicals like roundup before ,I'd advise you to contact a local forester or someone familular with there use.There are many alternatives.
You have to remember that roundup is very good at killing everything.even a few drops could kill if applied at the wrong time.
Also a few years back I sprayed roundup around young red oak seedlings,I used a stove pipe to keep spray off of trees,It worked great but that winter the exposed seedlings were easy targets for mice and rabbits and I lost almost every tree I sprayed around.
3-5 ft trees might do just as well with hand weeding? if there are not to many.

    Bookmark   June 16, 2007 at 6:13PM
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One thing that works well in tricky situations is similar to the "wet glove" technique mentioned previously: I pour some roundup into a small glass jar, and use a wide paintbrush to apply it to the weeds, while holding a piece of flat plastic behind them, so that they get a good soaking.
With a brush, its easy to control the amount you pick up, so that you don't spill roundup unnecessarily all over the place....

    Bookmark   June 16, 2007 at 8:29PM
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Jim Kochenderfer at the forest experiment station in Parsons, WV did a study of roundup applications to release Norway spruce from weeds and brush and hardwood seedlings/saplings. If anyone is interested I could try to find my copy in my very mixed up files--because of my move 5 years ago!

But I remember the basic idea of the study. Apparently a number of plantings of Norway spruce became overwhelmed with unwanted growth before their own growth could take off, hence the need for a release strategy. The crucial thing I can't remember and would have to look up is the concentrations used, but in essence, if the application were made late in the summer after the new growth of the Norway spruce had "matured" to a substantial extent, the weeds and the hardwood saplings and brush were killed and the Norway spruce was relatively unaffected. The applications were from aircraft.

So, if you think the spray could get on some of the conifers, I would wait until late summer/early fall. Of course the study I refer to was specifically NS and not the species you mention, but I would not be surprized if reactions were similar.

One strong note of caution--much of the roundup now offered is "roundup plus" or something, and it contains other herbicides which may be more harmful to NS than the pure glyphosate.


    Bookmark   June 16, 2007 at 9:24PM
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Some Glyphosate products are "fully labeled" for over the top application to conifers (christmas trees to be exact)WHEN the plants are FULLY dormant/during the winter/early spring. Typically in the USA, "Glyphosate Plus" products mean they contain a surfactent/wetting agent, not another type of herbicide.

    Bookmark   June 16, 2007 at 10:45PM
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I'm aware of nurserys making over the top apps of RU to fields of spruce in mid-late summer, when they felt the spruce were rather inactive. Supposedly it can work, but I did not think it appropriate for this poster to make such an attempt, so didn't go into that-'til now.

Yes, Roundup Pro has had some work done on the surfactants-still glyphosate.


    Bookmark   June 17, 2007 at 6:45AM
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Thank you everyone for your replies. Based on the responses, I think I will try Roundup near a few conifers later on this summer/early fall. The spruces, firs and pines all have lots of new growth still coming on despite our very hot and dry weather conditions.

I think the cardboard "shield" approach makes the most sense in my situation. The paintbrush idea is a good one as well, however because of the number of conifers we are dealing with (about 50 or so) that may not be practical.

Thanks again everyone. Much appreciated.


    Bookmark   June 17, 2007 at 8:02AM
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"I think the cardboard "shield" approach makes the most sense in my situation"

A stiff clear plastic shield is much better - you can see what you're doing better, and it won't get soggy and disintegrate.


    Bookmark   June 17, 2007 at 12:52PM
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ken_adrian Adrian MI cold Z5

do it all the time .... never lost a single tree ...

but you are lacking some facts upon which i will hesitate to tell you how to do it ....

are these landscape trees ... and are you prepared to put some work into the project???? once cleared of weeds are you prepared to apply a proper mulch to reduce the need to do this again?

or do you just want to spray willy nilly all over the trees to save time and hope to beat back the weeds??

if you are willing to do it right.. i will give you a plan to get the project done over a few week period .... some labor is needed ....

email me if you are willing .... at my garden web address ... and i will respond here [just in case i forget to check back] ...


    Bookmark   June 17, 2007 at 6:07PM
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Embothrium(USDA 8 Sunset 5 WA)

Cardboard can be disposed of afterward, if something like plastic is retained and reused it will have to be cleaned between uses - or handled in some other way so as to assure the spray coated side isn't put against the plants intended to be protected.

    Bookmark   June 18, 2007 at 3:08PM
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"or handled in some other way so as to assure the spray coated side isn't put against the plants intended to be protected"

The plastic shields used by UK forestry workers are curved, making it easy to remember ;-)


    Bookmark   June 18, 2007 at 3:50PM
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I used to put plastic funnels on the end of the wand on my sprayers. But it eventually became clear that there was no advantage. Just get used to your sprayer, and work carefully, paying max. attention to direction of spray stream. As far as shields, etc, again IMO no benefit. The real trouble are the weeds growing right in amongst the trees, and the shield will do nothing to help with this. With all due respect to others who have posted here, I can't possibly believe anyone has done the amount of glyphosate spraying that I have. In fact, as city horticulturist, I've often joked that I spend half my time growing plants, and the other half killing plants(weeds).

I guess whatever works for ya, but I know what really matters here. A good, non-leaky sprayer, an adjustible tip on the nozzle, and practice!


    Bookmark   June 18, 2007 at 11:01PM
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My friend needs help. RoundUp was mistakenly applied to several 6-to 8-foot pine their entirety. Is there a means of recovery? Any help much appreciated.

    Bookmark   June 27, 2010 at 1:42PM
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