Saving your garden’s cucumber seeds

By: Trish Grenfell
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How to save cucumber seeds

  1. Pick the largest, healthiest, most perfect cucumber specimens to harvest seeds. Be very careful that these cucumbers are disease-free since seed may transmit these diseases to next year’s seedlings. Remember that if you don’t pick ripe cucumbers, their vines will stop producing new fruit. Therefore, pick the seed-saving fruit toward the end of the season.
  2. Leave that fruit on the vine for 14 to 15 days past the stage it turns bright yellow or orange. At botanical maturity, the cucumber will be larger than its market-mature size, eventually losing firmness as the seeds reach full maturity.
  3. Just before the cucumber fruit starts to rot, scoop or press out the seed into jars of water and let this stand at room temperature for several days until the seed mass begins to ferment. The odor will confirm this has happened. The bad seed will float to the top with the pulp and the good, heavy seed will sink to the bottom. Skim the bad seed and scum off the top and throw it away. Wash the good seed in a sieve and spread to dry on screens or paper towels. Dry the seed as quickly as possible, but the temperature must not go over 96 degrees. Do not dry in direct sun. 
  4. Place dry seeds into glass jar or envelopes. Label all containers with the seed variety and date. To kill any remaining pests, put in the freezer for two days. Then store in a cool dry location like a refrigerator. Properly stored, the seed will remain viable for 5 to 10 years.

My friend asks, “Can I use my cucumber seed for next year? These ‘cucs’ tasted better than any I have grown before. I’ll just dry them out and save them in an envelope.”

I reply, “Well, it’s not quite as easy as that but I really am proud of you for wanting to make the effort. Gardeners and farms today wouldn’t have the fabulous heirloom varieties if somebody hadn’t kept their seeds year after year. Seed saving is essential for maintaining unusual or heritage plants and it is a frugal way to garden — but there are potential pitfalls. Let me ask you some questions.”

First, I explained that self-pollinating vegetables seed from tomatoes, peas, beans, and lettuce were the easiest to save. It is highly unlikely that another variety’s pollen would arrive at the scene and produce a seed not true to any of these vegetables. Unfortunately, cucumbers are cross-pollinated by insects and different varieties of cucumber will cross with one another. That must be prevented.

Then I asked her the crucial question; we needed to know if her cucumber variety was a hybrid, meaning a cross between two genetically different parent plants. Hybrid seeds will not reproduce true to the parent variety, may even be sterile, and are normally less vigorous and not as tasty as the parent plant. These hybrids are even seedless: Armenian, Persian, English, Kirby, Mediterranean and Japanese cucumbers.

Gardeners who use hybrid plant varieties must purchase new seed every year. However, if her cucumber variety were “open-pollinated” or “heirloom,” it could produce true-to-type seeds — with a little help from my friend.

Since she had kept her seed packet, we looked for the word “hybrid” or “F1” on it. Instead, we found the term “open-pollinated.” Hooray. It was indeed possible to produce seeds true to the cucumbers she grew this year.

Since cucumbers are cross-pollinated by many types of insects such as bees, wasps, beetles, butterflies, and moths, I asked her if her garden contained any other varieties of cucumbers whose pollen might have fathered her favorite cucumber’s seeds. Thank goodness, that was not the case. If her garden did contain two cucumber varieties, and she wanted to save seed from one of them, the only way to maintain purity in the favored variety’s seed is to isolate it from the other variety by large distances. Isolation is often impossible or impractical in a home garden, so a seed saver should grow only one variety. And that may not be enough.

According to UC Davis’ Agriculture and Natural Resources organization, cross pollination of cucumbers can occur from other cucumber varieties as far as 1,500 feet away. That is a little more than a quarter of a mile.

Anyone who successfully saves cucumber seeds deserves kudos and many opportunities to teach others. Nice to have that feeling of accomplishment.