Now that garden harvest is over, are you like many gardeners and have seed left over from last summer? If you are, Rhoda Burrows, SDSU Extension Horticulture Specialist, has some tips on which seeds can be kept over, which should be thrown out and how to best store seed so it’s ready to plant spring 2014.
“Most types of seed can be kept for a year or more if stored at the proper humidity and temperature,” said Burrows, referencing the chart for vegetables.
Among the more common flowers that seed can be saved from one season to the next: poppy, stock, and zinnia seed can last five years; marigold, hollyhock, and petunia seed for two to three years. Salvia and verbena seed can be stored for only one year.
Burrows said seed should be kept in a cool, ideally below 40 degrees, and dry location.
“A refrigerator can work well, as long as the humidity is kept low, or a deep freeze may be used. Ziploc freezer bags or other waterproof containers can be used to prevent seeds from absorbing any humidity released by fresh produce that you may have in your refrigerator,” she said.
When seed is in cold storage, Burrows explained that it respires at a very low rate, so it doesn’t need oxygen.
Prior to placing seed into storage Burrows said you can dry many types of seed to an optimal level by exposing them to 100 degree heat for six hours.
“Be sure not to exceed this temperature, or you may harm the seed and never use a microwave oven for drying the seed,” she said. “If seed is over-dried – beans and peas especially- the seed may have difficulty absorbing water when planted. If this occurs, you may be able to overcome this problem by placing the seed in a humid atmosphere for two weeks before planting.”
In the spring, Burrows said, you can test the seed germination by placing eight to 10 seeds on a moist paper towel and keeping it damp at room (70 to 75 degree) temperature. Count and remove the germinated seed daily for up to two to three weeks. Burrows reminded readers that if you decide to test your seed, you will need to allow yourself at least a month to carry out the test and to obtain other seed if needed.
“If you collect your own seed, be sure to follow guidelines for harvesting and storing it correctly, and never collect seed from an unhealthy or ailing plant,” Burrows said.
She added that it’s also not a good idea to save seed from a hybrid plant, as it may produce plants quite different from the parent plant.
When planning to save seeds, be sure to handle them with care.
“Larger seeds such as beans are fragile, and dropping a bag of the seed only a short distance onto a hard surface can decrease its germination rate significantly,” Burrows said.