- Author: Ed Perry
When planning your spring garden, one of the first decisions you must make is whether to use those seeds you saved from last year. Are they still as viable as they were when you purchased them, or will you be better off simply buying a new supply?
The answer depends upon the conditions under which the seeds were stored, as well as the length of storage. The two most important environmental conditions in seed storage are temperature and humidity. You should store all seeds under cool and dry conditions. An airtight, sealed jar placed in your refrigerator is a good way to do this. Stored in this way, many vegetable seeds will retain almost “first year” germination and vigor for several seasons. If you can't refrigerate your seed, at least keep it as dry and cool as possible.
The length of time seed is stored is not as critical as the conditions under which it is stored, but all seed deteriorates with time. Older seeds tend to require a longer time to germinate, and the seedlings do not grow as rapidly. Delayed germination and slow growth can cause young plants to be more susceptible to insect damage and seedling diseases. A delay in germination and growth can also delay maturity of the crop.
It's a good idea to test old seed before you plant. Place a few between moist paper towels and leave them at room temperature. Some seed normally takes longer to sprout than others, but if fewer than half of the seeds sprout or if they take an exceptionally long time, it's best not to use them.
Saving seed doesn't always save you money. In fact, it's more likely that losses due to poor germination and reduced vigor will more than offset any money you save by not buying fresh seed. However, buying new seed won't make up for poor planning. Even new seed will fail to sprout if it is planted at the wrong time of the year. If the seeds of warm season vegetable crops are planted before the soil warms up enough, they will often rot. For instance, the minimum soil temperature for seed germination of cucumber, cantaloupe, okra, pumpkin, squash and watermelon is 60ºF. However, at this temperature, the seed will not grow vigorously. A better soil temperature for those crops would be between 65ºF and 75ºF. Many summer vegetables require even higher soil temperatures for best germination and growth. For example, the optimum soil temperature for beans, eggplant, pepper, tomato and corn is 85ºF. As you can see, it doesn't pay to rush your planting.
Seeds need the proper amount of moisture and air in the soil to sprout. If the seeds dry out, even for a few hours, they will die. After you water, air enters the spaces between the soil particles as the excess water drains out of the soil. Since clay soils have less air space, seeds can suffocate if the soil is kept too wet. Mixing organic matter into the soil where you plant improves the soil's drainage and increases the amount of air in the soil. This will also help to prevent soil crusting, another reason seedlings often fail to appear.
Excess salts in the soil can burn tender plant roots. Soils with poor drainage may accumulate excess salts. Too heavy an application of fertilizer can also damage seedlings, so carefully follow the directions on commercial fertilizer products. If you use manures, mix them into the soil at least 4 weeks before planting and water heavily to wash out the excess salts they may contain.
Ed Perry is the emeritus Environmental Horticultural Advisor for University of California Cooperative Extension (UCCE) in Stanislaus County.
