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Summer 2011

Urban Jungle

The changing natural world at our doorsteps | Illustration and text by Patterson Clark      

Bitter Dock, Rumex obtusifolius

July 5, 2011

Bitter dock’s tiny, patient seeds

Standing in sharp contrast to the deep greens of July's sunny fields, the rusty-brown seed heads of bitter dock ripen and begin to loosen their grip on thousands of small, dry fruits.

Weak spines on each fruit — the seed and its papery covering — can briefly latch onto a passing dog or pants leg, which can ferry a fruit well away from its parent plant. The fruits can also ride the wind for a short distance or float for miles on a river surface.

Each fruit contains a single, sharp-angled, 1/16-inch-long three-sided seed, which probably won't sprout until the weather cools down. Bitter dock seeds germinate best in bright light, so if a seed becomes buried, it may not get the opportunity to sprout for a very long time. But it can wait . . . and wait, remaining viable in the soil for more than 50 years.

Sources: Journal of Ecology; Plant, Cell & Environment; gardenorganic.org.uk