How did a 2,000-year-old seed wake up?

A seed is a plant that is paused. Seeds have a built-in off switch called dormancy, an adaptation that prevents them from germinating in conditions that would give a seedling a low chance of survival. A dormant seed can wait through a bad season, and sometimes a very long time, until the signals say go. That is how a date seed from Masada, kept very dry for about 2,000 years, could still sprout when a scientist slowly gave it water, fertilizer and growth hormone.

Waiting has real benefits. Staggering germination, so that not every seed sprouts at once, protects some seeds and seedlings from short periods of bad weather or passing herbivores. Some seeds can remain in the soil for more than 50 years before germinating, and this is especially useful in fire-prone places. And a dormant seed is not dead or deaf: it appears inert, but it keeps receiving and responding to environmental cues.

Different seeds have different locks. Some have an impermeable coat that keeps water and gases out, and fire, freezing and thawing, drying or even a trip through an animal's gut can open it. Others contain chemical brakes, usually the hormone abscisic acid, and these wear off after a spell of cool, moist conditions. Some seeds, such as cocklebur and amaranth, germinate only in warm soil, while celery seeds are inhibited when the soil is too warm.

The most famous long sleeper is a date palm seed from Masada, Israel. Excavations at Herod the Great's palace in 1963 to 1965 revealed a cache of date seeds preserved in a jar, in a very dry and sheltered environment. Radiocarbon dating placed them between 155 BC and 64 CE. In 2005, Elaine Solowey slowly hydrated them in a baby bottle warmer and then treated them with fertilizer and growth hormone. Several sprouted. The first, a male named Methuselah, is the oldest seed germinated with human assistance.