Equisetum sylvaticum (Metsäkorte)

A close relative to E.arvense, but more symmetric in shape. As a weed E.sylvaticum is even worse. If not weeded of 3-4 times every year it covers all other plants with its lacy and actually beautiful foliage. And after some years I'd have only a lot of E.sylvaticum left. Tho root is strong and may be in 1 meter's depth in the clay. The only way to avoid the disaster is to pick all these plants up an do it often.