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large leafed weed in pastures with round spikey seed heads

05/24/2021: hello- we recently bought a house where the lawn was not maintained. These weeds popped uo this past week with all the rain and spears like crazy. looks like agrula. Any advice what it is so I can research how to stop it.

04/26/2021: 6” tall. Growing under fences where I sprayed Glyphosate last fall/summer. Have a few sporadic patches of this plant in my grass hay field.

Past Submissions and Responses

08/29/2020: So sorry, here is the attached photo for my previous submission. Thanks!

(Yes, I think that is it. Looked it up on other sites and it fits my description and experience. Thank you!)

09/26/2019: Found in pasture, largest clump about a foot high and wide, would like to know if it is safe for horses and how to eradicate.

While thistles respond to increases in soil fertility (and in particular nitrogen), management of all pasture types should aim to maintain pastures that have a good balance of perennial grass to legume content.

Biological control of thistles is a long term tactic and should only be seen as part of an effective integrated weed program. Up to ten insect species were trialled for released for the biological control of Onopordum thistles. The successfully established species shown below were released several years ago and are now present in most areas affected by Onopordum thistles. There should be no need for redistribution of these species. These biological control agents have a direct impact on the seed set of thistles. This is important for the long term control of thistles.

Acknowledgements

The flower heads are purple and round with spiny bracts. These bracts, surrounding the flowers, are the main distinguishing feature. They are sharp, needle-like and less than 3 mm broad at the base, yellow in colour, and only the outer bracts are reflexed (bent sharply backwards).

Stem-boring weevil

For populations of thistles where there is a mixture of sizes, spray in the spring before the flowering stem develops. If there is a flush of seedlings in the autumn an early spray can prevent the rosettes from colonising the ground and competing with the pasture.