This has been growing in my vegetable patch and I am not sure what it is.
This structure is growing at the end of a 30cm stem and there are a few of them growing quite close together.
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It would have been better to see a photo of the whole plant, but judging by what's there, its a Euphorbia of some variety. These are often difficult to dig out, because the roots can go down quite a way. Confirmation of it as a Euphorbia is if it produces white sap when you break a stem - that sap can be highly irritant on some people's skin, so wear gloves when handling this plant.
There are hundreds of varieties of this plant available for purchase, but also many that pop up as weeds, or have been deliberately planted and are persistent despite attempts at removal. Example of a similar one here: Euphorbia microsphaera Boiss.