I just got done carving out a space for Japanese ”White Pear” melons from the weeds between a young persimmon tree and the woodshed. Its good dirt, though someone had put a small pile of rocks there years back. I dug it with a maddock and fertilized it with chicken manure and ashes. Now it’s a small melon isolation plot, big enough for about eight plants.
This is what I do in the evening, when I’m done working with the seed crops in the fields.
The Cucurbit Family: In Need of Isolation
As a seed grower I’m often thinking about how to find more isolated plots for seed growouts, and about exactly what to put in those plots. Some kinds of crops, like cucurbits, need a lot of isolation. The cucurbit plant family, which includes melons, watermelons, cucumbers, squash and gourds, is pollinated by insects. Different varieties of the same species that are planted near each other will inevitably cross because the bees transport the pollen between the flowers. Cucurbit varieties of the same species need to be isolated by at least ¼ mile to prevent crossing. For large plantings, or if there are few barriers between the crops (like trees, or flowering plants) the isolation may need to be half a mile or more.
I am up to three field-sized isolation plots and five garden-sized isolation plots for cucurbits. I live in the country and I’m a full time seed grower. I know that most people aren’t going to go for eight isolation plots. But I want to share the basics of how to plan your garden for seed saving, starting with cucurbits. Note that what I have to say here is about saving seeds from open pollinated varieties, not hybrids. It is possible to save seeds from hybrids, and this can be a good starting point for new breeding projects. But the next generation of plants will be highly variable and not like the parents.
If you have one garden that is sufficiently isolated from neighbors’ cucurbit plantings, you can grow one of each cucurbit species at a time. So one cucumber, one melon, one gourd, one watermelon, and one of each squash species. There are four major species of squash, which generally don’t cross with each other. Ideally you’ll have a handful of plants of each variety, but with cucurbits it will still work with one or two plants.
Know Your Squash Species
Here is the quick rundown on squash species: Cucurbita pepo is the most common and includes a wide variety of types. Zucchini, yellow squash, acorn squash, Halloween pumpkins and small decorative gourds are all pepos. You can get some wild crosses between pepo varieties because they are so different. Cucurbita maxima includes 'Buttercup,' 'Kabocha' and 'Hubbard' type winter squash, as well as giant pumpkins. Maximas tend to be more adaptable to cool climates. Many varieties have excellent dry sweet flavor. Cucrbita moschata includes butternut squash, cheese pumpkins, and most tropical pumpkins. Fruits are tan or green. Many Moschatas have a long growing season, and the species tends to be more adaptable to warm climates than pepos and maximas. Cucurbita argyrosperma (mixta) includes cushaw squash. It tends to grow well in warmer climates.
Hand Pollination: When It's Appropriate
What if you live in town and there are neighbors growing these crops already?
Living nearby other gardeners will significantly complicate the situation, but there are still options. First, talk to the neighbors and find out what they’re growing. Maybe they would just as soon grow the same kind of cucumber as you. You could offer to provide the seeds.
Second, you could focus on some of the less common cucurbits, i.e. not cucumbers and pepo squash. Even though melons and winter squash are common foods, home gardeners are not as likely to grow them.
Then there is hand pollination. With hand pollination, you don’t need any isolation at all, and you can save seeds from many varieties at once. It’s more work though, especially if you want a significant quantity of seeds. It’s something to learn and to be on top of at a time when there's usually a whole lot else going on.
I have a confession to make, which is that I have never done hand pollination. This year I’m going to learn though for sure, because of the breeding projects I’m doing and that I want to do. Eight isolation plots just aren’t enough, and besides I want to make all kinds of crosses. You can count on seeing a post from me about hand pollination this summer.
One more option – time isolation. You can grow two different cucumber seed crops in the same garden if they’re sufficiently separated by time. Planting dates a month apart should work, preferably with the first planting being a shorter season variety. I have done a good bit of time isolation. The main drawback has been Downy Mildew, a cucurbit disease that is much more severe on late plantings. Downy Mildew is a big deal in the Southeast, mid-Atlantic, and parts of the Northeast and Midwest, but not much of an issue elsewhere. Finding Downy Mildew resistant varieties has become a major focus of my work, and the focus of our variety trials. More about that later. Time isolation will also be difficult in areas with a short growing season.
Why save your own cucurbit seeds? There are a lot of reasons, but for now here are two:
By saving your own seed you can adapt varieties to your particular conditions and preferences. I have seen just one season of selection make a big difference. Most seed companies buy seeds from around the world that aren’t adapted to your region let alone your garden.
Seeds are an essential part of our collective heritage. Most of our ancestors were involved in taking care of seeds. What has become clear in the last 50 years is that seed saving something is not something we can just hand off to seed companies and corporations. Saving and stewarding our own seeds, and being in a network of people saving seeds, is essential if we aspire to be in control of our own food supply.