By Dt85
United Kingdom 
Do you know what this is please? It's on a self-seeded plant and has been there a few years. It's on a spindly stem with thorns like rose and leaves in sevens like a wild rose.
7 Aug, 2015
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« Thank you for your replies Please how do I take cuttings from my lavender
That is a gall, commonly known as Robin's Pin Cushion. It is the plants reaction to a small wasp laying its egg under the bark. Bit like an oak apple on Oak trees. It actually does the rose no harm, but it if offends you, just cut out the stem below the gall.
7 Aug, 2015