Saving seeds from heirloom or open-pollinated cucumber varieties is a wonderful way to ensure the plant's vitality. Selecting seeds from the fruit with the best qualities tailors the variety to the specific conditions in your garden, allowing a fruitful harvest for years to come. But saving cucumber seeds is a little more involved than saving bean seeds, which you simply pick, dry, and then store. Unlike beans, cucumbers need to be pollinated by insects or the wind (or hand-pollinated by the gardener) to set fruit. To complicate things further, cucumbers cross-pollinate easily with other cucumber varieties. Professional seed savers recommend isolating cucumber varieties by a 1/2 mile to prevent crossing. Since most home growers don't operate large-scale farms, isolation for seed collection requires specific measures.
Isolating Cucumber Plants
The first step to saving cucumber seeds is to isolate your plant before it fruits. One way to do so is to bag individual female blossoms before they open (the ones that look like they have a tiny cucumber at the base) in spun polyester or cotton bags to prevent insects from pollinating them. Then, do the same with an adjacent male flower. Tag the branch with the female blossom so you can identify it later as the one you'll harvest for seeds.
Another way to isolate a cucumber plant involves building a cage that will enclose the entire plant. A wood or PVC frame covered in a spun polyester screen works great to keep pollinators out.
Hand-Pollinating Cucumber Flowers
You don't want undiscerning bees pollinating the cucumber plants from which you'll be saving seeds. So, this is where you play Mother Nature yourself. First, use a small brush to collect the pollen from the bagged male cucumber flower. Then, place the pollen onto the stigma in the center of the female flower. Re-bag the female blossom until it ripens into a fruit. The presence of fruit assures that your hand-pollination methods worked and you can safely remove the bags. But make sure you keep this fruit tagged, so it doesn't end up in a salad by mistake.
Harvesting Cucumber Seeds
Any cucumber cultivated for seed must be grown to full maturity and remain on the vine past the point where it is no longer edible. The cucumber will be larger than its usual harvest size and will start to soften. It will also change in color from green to whitish, assuring it's time to harvest.
To harvest the fruit and collect the seeds:
- First, pick the giant cucumber.
- Next, cut it lengthwise revealing the inner seeds and fruit.
- Scoop the contents into a bowl and then add water to cover.
- Set the bowl aside in a warm, sheltered spot to begin fermentation (much as you would if you were saving tomato seeds). Fermentation can occur in as little as one to three days and will be marked by the seeds sinking to the bottom of the dish.
Once all your seeds have sunk, add additional water to the bowl to clean them. Any debris or unviable seeds will float to the top, making them easy to skim off and discard. Rinse the good seeds a few more times, strain them, and place them on paper towels or uncoated paper plates to dry. Once dry, store the seeds in a zippered storage bag or a Mason jar and label them for next year's sowing.
Stored properly, cucumber seeds will remain viable for 10 years.