Storing leftover seeds correctly from one growing season to the next reduces waste and can save money. Keeping seeds in a cool, dry location such as a basement or even the fridge can preserve their viability. Whether stored properly or not, there are simple methods you can take to determine if your seeds from seasons past will perform for you again in the upcoming garden.
Place 10 seeds of a single variety a few centimeters apart on a damp paper towel and fold the towel over itself to cover the seeds. Seal the towel in a plastic bag. Mark the date and plant variety on the outside of the bag. Repeat this process for each variety of seed you want to test. Keep the bags in a warm location. Watch for sprouting based on the days to germination listed on the seed packet. Typically, 7 to 10 days is a reasonable amount of time to start checking for growth. When you notice sprouting, unroll the paper towel and count how many seeds are active. If, for example, only five out of the 10 seeds of one variety have germinated, you can expect a 50% success rate for those plants to grow in your garden as well.
Following this germination test process will help you decide which seeds need to be replaced and which ones will produce acceptable results for the garden. Seeds that have sprouted from your germination test can be planted in a container and protected indoors until it is safe for outdoor planting. Carefully tear the paper towel around each sprouted seed and plant them in the soil with the paper intact. This will prevent damage to the fragile root system. Edible varieties such as lettuce and spinach can be harvested after about a week of growing and consumed as microgreens.
A second method of evaluating seed viability is the float test. This is primarily for larger seeds such as melons, beans and corn. Place the seeds in a bowl of water. After several hours note which seeds are floating and which have sunk to the bottom of the bowl. Seeds that are not viable will float to the top because they are incomplete, potentially lacking an embryo or carbohydrates and are essentially hollow. Seeds that sink to the bottom should still be intact and suitable for spring planting.
When gardening with expired seeds, sow more thickly to compensate for the lower germination rate. You can always thin your plants out if too many germinate. This will help prevent the disappointment of sparse sprouting while also not wasting seeds.
Now you’re ready to supplement your collection by ordering more seeds. It is easy to become overwhelmed by the selection of plants available while perusing the seed catalog and you may find yourself spending more time on this task than anticipated. Keep a list of what you will plant of your seeds from last year along with a list of seeds to purchase. Knowing in advance which plants you positively want to grow, those you are considering growing again, and the plants you do NOT want to grow again based on previous years’ experiences will help you stay on track and within your budget in terms of money and space.
Cynthia Domenghini is an instructor and coordinator for K-State’s horticultural therapy online certificate program.