If you remember from Seed Saving Nerd Out (SSNO) Part 2, two categories of plants require isolation for your saved seed to breed true: Insect- and wind-pollinated open-pollinated crops. (It's a mouthful, I know. This chart helps organize the concepts.)
If you want to save pure seed from a wind- or insect-pollinated variety, you have two choices: Separate plants that could cross-breed by their specified isolation distances (almost impossible in urban and suburban areas) or pollinate it yourself, and then keep other pollen out.
This post will show you how to pollinate zucchini for seed saving.
(Hand pollinating also increases yields for all types of squash. If you have lots of flowers, but few squashes, this technique will help!)
Step 1: In the evening, identify one male and one female flower poised to open, and tape them shut.
If you don't yet know how to identify flowers about to open, spend a few days checking on your zucchini in the evening and then again in the morning to see how the flowers look in their various stages.
Identify female flowers by the mini-zucchinis at the base. Male flowers are on a plain stem.
This is a male flower, taped shut, at night. You can see the plain stem below the blossom.
This female flower has a mini-zucchini at the base. You don't have to go out and tape them shut in the dark (evening is fine), but it was pretty exciting rummaging around in the plants with all the night insects buzzing around my headlamp!
Step 2: The next morning, find your flowers and remove the tape.
When you see the flowers in the morning, it's easy to tell why you taped them shut. They're bursting to open! They open early in the morning and pollinators will get in there before you. (I hand-pollinated and took these pictures at about 7am, and the pollinators were already busy on the open flowers.)
Step 3: Pick the male flower and remove its petals
This makes a little pollen paintbrush for you!
Step 4: Rub the pollen all over the inside of the female flower.
Get that pollen all over the structures at the base of the female flower.
Step 5: Net the female, and mark it. (Skip this step if you're just interested in bigger crops, but not seed saving.)
Now that you've pollinated your zucchini flower with pure zucchini pollen, you don't want any bees coming along with other squash pollen to contaminate your seeds. So either tape the flower shut again, or net the flower. I'm using one of those reusable net produce bags because the drawstring at the top makes it easy to close. But really anything that keeps the bugs out will work.
I've also got a pink bow that will stay on the zucchini all the way until harvest so I know which one is for seed saving. (I'll probably have to loosen and move the bow as it grows!)
Now we just wait and watch it grow until the skin is hard. I'll post an update when it's time to collect and harvest the seeds.