I found this plant today which I knew was Knotgrass but thought it would be fun to find out which. As it turned out it was rather more difficult than I imagined. It was the key in Stace that got me to the conclusion in the end by the 3mm length of the achene (dry fruit of a flowering plant). There was a mention of silvery sheaths later turning brownish in Domino Guides which I could see. Polygonum arenastrum (Equal-leaved Knotgrass) is the one I had most trouble with. P.arenastrum is said to have leaves on the stem and branches roughly the same but the leaves on the stem were different sizes making this feature difficult to determine. Maximum size of achene on P.arenastrum is said to be 2.5mm therefore not my plant.
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| Polygonum aviculare achene 3mm in length |
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| Polygonum aviculare |
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