Dodo Trees and Box Turtles

—Taro Ietaka, Director of Conservation and Land Stewardship

It is scarification and stratification time. Gardeners know those to be tricks to get seeds to germinate. It's not necessary to fool a tomato seed into sprouting -all that is needed is warm moist soil. However, seeds from less domesticated plants still need to be tricked into thinking they've gone through a winter, a fire, or even an animal's gut before their little green shoots will emerge.

Stratification is accomplished by mimicking a winter's passage. Seeds of milkweed, false indigo, apple, oak, and many other plants from northern and temperate climes are put in cold, moist storage for a month or two before being planted. The cold and moisture weaken the seed's hard coat and waken the embryo within.

Scarification involves scratching a seed's coat or putting it in acid or hot water. This is sometimes done for seeds that are contained in a berry or fruit; in nature, the seeds are swallowed along with the fruit and are scratched by teeth and bathed in stomach acid before being expelled in manure.

The hard seed coats that protect the embryos within do their job admirably, but problems can arise in the wild if there is no one to eat the containing fruit. The Dodo Tree (Sideroxylon grandiflorum) nearly went extinct in its native Mauritius and it was theorized (although now contested) that the reason for its lack of regeneration was that there were no more dodos left to eat the fruit. As a result, embryos remained trapped in their un-dodo-scratched seed coats.

Mayapples produce a bite-size fruit at the perfect height for a box turtle's mouth.
(Podophyllum peltatum by Velocicaptor

A local example of the intertwined fates of seeds and animal stomachs is the mayapple (Podophyllum peltatum) and Eastern box turtle (Terrapene caroliniana) connection. A study in 1987 by Braun and Brooks found that Mayapple seeds, along with wild grape, pokeweed, and others, germinated more efficiently after they had passed through the digestive systems of Eastern box turtles. As box turtles decline locally because of development and predators, mayapples may find themselves without their animal partners to scarify and scatter their seeds.