Hairy Bittercress / Cardamine hirsuta and / or Cardamine oligosperma

Asked November 9, 2019, 5:42 PM EST

This seems to be "everywhere" as far as seeing it "here there and everywhere". We may or may not have had it here (O'Brien) prior to us realizing it's invasive and fast spreading nature. Originally when we first noticed it here, we thought it came in with some fertilizer (which is probably did as well - as we'd been unaware of it prior to then); however, as it seems to be everywhere now (locally, Grants Pass, Medford, Ashland, etc.) , and even more places on our property, it would seem that could not have been a sole source, and perhaps it was already here(?). We have worked hard over some years to curtail it, especially around our house, in the dog run and garden, and our gravel road it. However, even that has proved all but impossible as far as really getting rid of it. We thought we'd made a semi decent dent in things, but then this fall it is showing up, prolifically, in places we'd never even seen it before. Theoretically the hirsuta is non-native and the oligosperma is native; is that correct? Not that it does a lot of good though, since they both pose the same problems. Obviously we will never be able to be done with this, and at this point it is so overwhelming and beyond our capabilities, all we can hope for is a miracle to be able to try and keep it from amassing in the areas I mentioned. In years past, we tried pulling some but that soon became futile, so the best we can do is herbicide and do our best to do that before they flower. With 90+ acres of forested area, there simply isn't anything we can do but try to live with it. Unlike Scotch Broom, it isn't a fire hazard, but it is overwhelming and stressful not being able to do anything to control or curtail it. Your thoughts? (Thank you)

Josephine County Oregon

6 Responses

Bittercress spreads through prolific seed production. So managing seed set and the existing soil seed bank will improve long term management in areas you wish to protect from invasion. One good way to do this is through the use of preemergence herbicides. The herbicide Snapshot (trifluralin plus isoxaben ) has excellent activity on both bittercress species. It needs to be applied in the fall prior to rain to control germination. For existing plants, control can be achieved with broadleaf herbicides such as 2,4-D or dicamba or non selective herbicides including glyphosate. Try to control them prior to seed set which happens very quickly as you well know.

Thank you Andrew. If I may ask further.
Are either of these "native"? And will they at all self regulate?
I do not have the wherewithal on multiple counts to deal with these, especially additioanlly this fall with more larger new areas than prior. I can only attempt some where I can, and continue with RoundUp.
What will happen as I am more and more unable to tend to these at all?
Thank you; could so use something encouraging, on so many counts.

Cardamine hirusta or hairy bittercress is native to Europe. Cardamine oligosperma or little bittcress is native to the western US. They are often difficult to tell apart an often co-occur. I dont think they will "self regulate" and will continue to be weedy species on your property spreading by seed. I would continue to use the glyphosate as needed in areas you want to keep free from these species.

Thank you again Andrew.
No way can I handle or keep up with this, but must try, best I can, at least in higher trafficked areas.
What perimeters have you had best luck with for spraying?
Temperature range, and how long ahead of rain?

Spray glyphosate products mid morning to mid day and never in the evening. Temperature above 40 best. Need 3-4 hours drying time for most products prior to significant rainfall.

Thank you, again, Andrew.
All I can do is try and pray.