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When is a seed too old to sprout?

In the 1960s, the palace of Herod the Great was excavated at Masada, Israel. There a container of date seeds was found perfectly preserved in a sealed ceramic jar. This 2,000-year-old species successfully germinated into a Judean date palm of a kind that had been extinct for more 1,800 years.

Seed viability is as important to today’s gardeners as it was in the dawn of agriculture.

A seed is viable only if it is able to sprout and put down roots. That viability is governed largely by genetics. This factor is the chief weakness of seed banks, because even under ideal storage conditions, some seed just isn’t genetically programmed to retain viability for very long.

The only way to ensure plants are available for the future is to keep them in continuous cultivation so there’s always a seed crop for next year. This was the original goal of the heirloom vegetable craze that keeps obscure varieties from dying out, and perhaps one day it will become the salvation of a changing climate.

Viability also can be influenced by environment. The date palm seeds from Masada remained viable because they were in a dry climate, in the dark, and protected from temperature change by insulating earth. Put those same seeds in moisture or a lighted room and they might have lost viability early on.

Seed can also lose viability gradually while in storage. A packet of seed may experience 100 percent germination the year it was packed. If not used immediately, 10 percent of the seeds may die the second year. Each year that follows may lose another 10 percent.

At the end of a gardening season, everyone has leftover vegetable seed. Store it properly and you can reuse it next year. Each packet is printed with the date it was packed, which is the current year for seed you purchased this past spring. Savvy gardeners are always careful to open a seed packet in a way that doesn’t tear off the date stamp.

Some gardeners prefer not to take chances, so they new seed each year. In the frenetic activity of spring and summer gardening, leftover seed is often set aside without any further protection.

Late fall is a good time to go through the leftover seed packets to organize and prepare them for storage. If you lost the packing date, write it on the packet. If you lost the packet, put the seed in a recycled envelope labeled with the name of the variety, current year and notes. Seal each packet with tape to make it airtight. Don’t throw out the empty packets; just clip them together by year and store. These come in handy when selecting seed for next year’s garden to remind you what varieties you planted and whether they’re worth trying again or not.

The best container for seed storage is a clear plastic box with a tight-fitting lid. Choose one you can store under your bed where it’s cool, dark and dry.

Clip or print this seed viability list to keep in your seed box as a guide. Then put it all away until spring, when you’ll appreciate this reminder of how old is too old to replant for success.