Safe herbicides for 2 yr old fir trees

Asked January 20, 2021, 2:11 PM EST

We have 25 acres zoned forestry in Alsea area of Benton county and we planted 3500 Doug fir trees one year ago today that we bought from Brooks tree farm. We didn't know what we were doing so we didn't spray weeds or grass and now we are dealing with the grass choking out our trees. We have black berry bushes and scotch broom weed taking over and choking some of our baby trees. We have lost over half of them so far. Is there a spray we can use that is safe for the trees but will kill the weeds and grass? Please help any advise you give us will be appreciated. Thank you

Benton County Oregon

1 Response


We should talk rather than me try to give guidance without details. Is there a number I can reach you? In the meantime, here is some helpful general information for you to look over before we talk.

Brush species can be controlled a number of ways (foliar spray, cut surface). Our preference is always to do as much as possible before planting, since it is harder and riskier after your trees are planted. Timing is important.

We have written a number of short blog articles about weed control that can be viewed by following this link.

I’d recommend looking at the 2013 series on using foliar herbicides.

Another, from 2016 “resources in the fight against weeds”, includes links to the PNW weed control handbook that will give you very useful information about controlling specific brush species, safety and such. A great resource.

Grasses can also be controlled by foliar sprays, as discussed in some of articles above. They will generally return from the soil seed bank after they are treated, so it often requires several treatments in the season to get good weed control established well before the rains end.

There is also an option for soil active pre emergent herbicides, which can provide weed control for a whole season. We would need to discuss that.The challenge for them is that they need to be applied at a per acre basis, which can be done very well with a back pack sprayer. But you do need to calibrate. There are a couple blog posts on that too, from February 2020, that will be right at the top when you follow that blog link.

I should also remind you that herbicide application is a forest operation covered by the Oregon Forest Practices Act, and thus requires notification with the ODF. You can get a good overview of the forest practices rules in the illustrated manual produced by OFRI. Notification is covered in the introduction. It can all be done online now. This is from page 6.

File a Notification of Operation as required. After you’ve planned the operation, submit a Notification of Operation via the E-Notification website at least 15 days prior to the start of the operation. Failure to file is a violation under the Forest Practices Act and Rules. For more information, see E-Notification at

So, that is a lot of information. Please look it over before we talk. It may not all make sense, first time through, but it will help us move forward in our conversation. It will be important for you to get a good broad understanding now, to help you plan an approach, with time to work out some details in weeks or months ahead.