The trick was botanical rather than clever. Larch is one of the few deciduous conifers, dropping its needles every autumn and putting out soft new ones each spring, so a block of larch set inside a pine plantation will spend most of the year almost invisible and then, twice annually, blaze a different colour entirely. Whoever laid out the planting understood this. They also understood that the pattern would be meaningless at ground level: walking through the stand, you would register a change in tree species and nothing more. The design existed only in plan view, at a moment in German history when almost nobody had any reason or ability to look at rural Brandenburg from above.

Reports place the planting in 1938, and there the certainty ends. One account holds that it was made to mark Adolf Hitler's fiftieth birthday, though that fell on 20 April 1939 — a mismatch that has never been resolved. The work has variously been attributed to local Hitler Youth members and to a forest warden acting on his own. No planting record, no order, and no confession has surfaced. Then came the war, the division of Germany, and forty years in which this corner of the countryside sat inside the GDR, where aerial photography of one's own territory was not a casual civilian pastime. The pattern simply grew, unremarked, through decades of a state that defined itself by its opposition to the regime that made it.

In 1992 an employee of a landscaping company was studying aerial photographs of the area, looking for irrigation infrastructure, when the shape resolved out of the pattern of trees. It is a small, strange detail of German reunification's aftermath: not archives or monuments, but a routine survey turning up something that had been quietly waiting in a forest for more than half a century, visible the whole time to anyone who happened to fly over in the right fortnight.

Brandenburg's state authorities had two worries. One was straightforward damage to the region's image. The other was that the site might draw National Socialist sympathisers and become a place of pilgrimage. In 1995 they had 43 of the 100 larches felled, which should have settled it. It did not. The remaining 57 trees, helped along by regrowth, kept the figure legible, and in 2000 German tabloids published fresh aerial photographs showing it as plainly as before. By then roughly half the land beneath the trees had passed into private ownership, complicating any further clearance. Permission was obtained for the government-owned portion, and on 4 December 2000 a further 25 trees came down. That largely obscured the shape. The point was never landscaping. Twice, five years apart, the state chose to cut down healthy trees rather than let a Nazi symbol stand as a landmark or a pilgrimage site — a decision about what a place is allowed to mean, not just what it should look like.

Zernikow's was not unique. In the late 1970s American troops in Hesse came across a swastika planted in the same manner alongside the numerals 1933; who put it there has never been established. In September 2006 The New York Times reported a mirror-image fir-tree swastika roughly 200 metres across at Eki Naryn in Kyrgyzstan, on the edge of the Tian Shan, its origins buried under competing local stories. Not all such plantings carry that weight. On Monte Giano near Antrodoco in central Italy, pines were set out in 1939 to spell DVX — the Latin form of Duce — as part of a scheme to stabilise the slope against landslides, and they remain. And in Oregon a stand of larch planted in 2011 among pines makes a smiley face that drivers can pick out on Highway 18 between Grand Ronde and Willamina every autumn. Foresters have always known that a plantation is a message written slowly. Not every message carries the same weight, and not every message deserves to stand once it's read — which is exactly why Brandenburg spent five years and two fellings making sure this one didn't.