This is where seed saving can become very difficult. Like the seed saving posts from the last few days, I’m going to focus here on the simplest aspects of out-breeding plants. Let’s also be very clear here, I have about 5 years experience with seed saving. For some people that may make it seem like I am an expert, but many people spend their whole lives working in this field and are still learning new things. In fact anyone who tells you they don’t have anything new to learn about seed saving is probably lying to you. Even well known published books on the subject come out with new editions and changed information, as opinions change and new information is uncovered.
Think of this post as something to get you started thinking on this subject, not a how-to guide! Also remember everything I say here is a guideline, not a rule. The great thing about seed saving is you can do whatever you want! Your plants belong to you, and the whole point is that you should be growing the plants you want to. If ignoring something I or anyone else says on this subject means you grow something more interesting, it’s a good thing. There is also nothing lost by experimenting. Just be sure to be honest with anyone you share your seeds with about what they should expect!
Be sure to start with the right kind of seeds!
New Page
Because there are now many people reading this blog, with many different backgrounds and skill levels on this subject, I’ve created a new Common Terms page that appears on the front of this blog. This page has some definitions for common terms and concepts related to seed saving and plant breeding, and I’ll be regularly adding new things to it. As an alternative to explaining these concepts every time I post about them, I will link to this page instead.
Good Books on the Subject
If you want to read more and probably more accurate information on this subject, these are two good books:
Carol Deppe’s Breed Your Own Vegetable Varieties: The Gardener’s & Farmer’s Guide to Plant Breeding & Seed Saving
Suzanne Ashworth’s Seed to Seed: Seed Saving and Growing Techniques for Vegetable Gardeners
The Issues
There are three main issues with out-breeding plants, inbreeding depression, rouging and cross-pollination.
To avoid inbreeding depression you need to save seeds from enough different plants of the same variety at the same time.
To avoid unwanted traits from entering your plants genepool you need to rouge out or remove plants with these traits.
In order to avoid unwanted crosses in your garden, you need to make sure your plants are isolated from other genetically compatible plants.
At the Simplest Level
If you have an out-breeding plant you want to save seeds from, just take into account these three issues and nothing more is required.
The number of plants needed to avoid inbreeding depression varies, but is generally between 5-200. Obviously more is better, but 10-20 is a reasonable number for most plants. If you can manage 200 plants, you are virtually assured to avoid the problem. In any case, problems with inbreeding depression will not show up for a few years, so you are very likely to end up with at least a few generations of plants regardless of how many plants you manage to save seeds from. If you know your genepool is limited, and inbreeding depression in future generations is likely, don’t share your seeds without warning the next person!
Be sure to rouge out plants that bolt early, are stunted or in any other way deficient. When considering inbreeding depression, and how many plants you will need to avoid this, remember to plant some extras so some can be rouged out and you will still end up with enough plants.
You don’t need to worry about very unrelated plants crossing, for example a cucumber will not cross with a watermelon, but otherwise make sure there are no similar plants blooming anywhere in the area at the same time yours are.
That’s it!
Some out-breeding annuals to try in this way are pumpkins and squashes, cucumbers, some herbs like basil, sunflowers, fava (broad) beans, lima (butter) beans, melons and spinach.
To avoid vitality problems with the seeds, be sure not to eat from the same plants you save seeds from. The plants should put all of their energy into the seeds.
Where Does it Get Difficult?
The problem is most people want to save seeds from more than one variety at a time, or cannot be sure their garden is properly isolated from other genetically compatible plants. Also, determining exactly what is genetically compatible or the true isolation distance required can be very difficult, and often requires some trial and error. In cases where sufficient isolation distances can’t be maintained, you need to use techniques like caging, bagging or hand pollination. Rouging can also be more difficult for example if assessing a plant for deficiencies involves a root crop buried in the ground, or a vegetable that forms after cross pollination takes place.
Biennials can also be considerably more work than annuals. Among the issues to be dealt with, they go to seed their second growing year requiring more time and space in the garden and often need special care to survive the winter in colder climates. Biennials also often require larger genepools to avoid inbreeding depression.
Perhaps in some future posts I will address some of these issues, and discuss seed saving from specific plants.
Goodness, that’s a bit more complex than I thought: inbred plants. I can see why a seedsaving group is such a good idea.
If you buy all of your open pollinated seeds from the same source would that also add to inbreeding?
Hi Blue,
That’s a really good question, and I can see you really thought about what I wrote.
Inbreeding depression is a yes/no kind of thing. For example, it’s not like biodiversity where you can always improve on the situation. If seeds are saved correctly, inbreeding depression is not a problem and you don’t need to worry about it.
For this reason, it’s very important to trust your source of seeds. A proper seed company should know what they are doing, and should not sell you bad seeds. If you get out-breeding seeds through a seed exchange, or from another gardener, it’s always a risk. It’s better to get them from someone you trust. This is another reason why seed savers tend to form circles of friends, so they can get seeds from people they know.
If for some reason you think some seeds might have too small of a genepool, and are at risk of developing inbreeding depression, combining them with seeds from another source may save them, but it’s probably better to just discard the suspect seeds and start over again if that’s possible.
But also remember what I said before, plants that are mostly inbreeding are very resistant to inbreeding depression, so you don’t really need to worry about it when it comes to these kinds of plants.
Many seed savers just don’t bother with out-breeding plants, so they don’t need to worry about inbreeding depression. There are other seed savers who save seeds with the intention of discarding them after using them for a few years, so also don’t worry about inbreeding depression. This issue is most important when you intend to share the seeds with other gardeners or are trying to preserve a rare variety.
I’m looking for someone with seed-saving experience who might be interested in adopting a sweet basil plant which has survived repeated cold nights here in Santa Rosa CA. If it can be persuaded to bloom & mature its seeds, they might carry some unusual genes for cold-hardiness; I suppose it could be a “sport.”
This plant was one of several which I had potted up in the fall and set by the south side of my house. After this plant had long outlived all the others — weathering quite a few cold nights, including one which was reported as 27 degrees — I decided not to take any more chances with it; so I started bringing it indoors on cold nights (to an unheated room, under a slightly open window). It still has a few clusters of green leaves. I’m hoping to find someone with more experience than I have, who might be able to successfully get seed from it and perhaps breed a reliably cold-hardy strain.
Or maybe someone can simply tell me how to get it to do its thing! I don’t have a large garden, but I could devote one bed (approx. 48 square feet) to a basil-breeding experiment.
But since I read here that basil is an outbreeder (that’s how I found you, researching that matter), I have another question — it’s not actually self-sterile, is it? I don’t find any indication of that in several pages of Google results. If it is, and it decides to bloom in midwinter, I’d be out of luck.
… I contacted Carol Deppe, who wrote “Breed Your Own Vegetable Varieties;” but she has no interest in basil & very little familiarity with it.
p.s. One website did say that there are perennial as well as annual varieties of basil. I’d never known that! It would be great if someone could develop a cold-hardy, perennial basil (which might stay green all year in a reasonably mild climate).
Hi Chamundi,
I don’t have a lot of experience with Basil.
According to Suzanne Ashworth’s Seed to Seed, basil is a mostly inbreeding plant, insects are needed for pollination and can carry the pollen from plant to plant, but isolation of 150 feet (50 meters) is enough to prevent cross pollination. It’s certainly not self-sterile.
If your plant is a commercial F1 hybrid, it will be very difficult to save seeds in order to develop your own variety.
I live in Holland, which doesn’t allow the import of live plants and I’m also not interested in basil right now, so I can’t take the plant. I don’t know of anyone else in the Bay Area either who might be interested.
Anyway, good luck and best wishes.
Thanks for the information! Odd, though — if basil requires insects for pollination, why would it be mostly inbreeding? I wonder if perhaps they’re required for a cross but not for inbreeding. Thoughts?
I don’t know the background of this plant — I just picked up several sixpacks last spring at the nursery — but I think I’d have remembered if one was a hybrid, since that would’ve been a surprise to me. So I’ll proceed on the assumption that it’s not a hybrid, unless the next generation proves me wrong.
Do you happen to know what conditions basil needs in order to flower, like whether daylength is a factor, or perhaps warm nights?
Here are some pretty good pictures of the flower.
From these pictures you can see why an insect would be needed to carry the pollen to the stamen.
I don’t know why it’s a mostly inbreeding plant. The flowers look pretty open to me, suggesting it would be easy for pollen to travel from plant to plant. Maybe there’s some other factor that limits the pollen’s ability to travel long distances or encourages pollinating insects to stay and keep working on the same plant.
I don’t think it’s day length sensitive, but I don’t know. There’s nothing in Suzanne Ashworth’s book that says it is, and I didn’t find anything in the little bit of Internet searching I just did. Except for normally being sensitive to cold, and not tolerating very warm weather, I didn’t read anything to suggest the plants are sensitive to temperature.
Good luck!
Thanks for the picture! Looks like I would be able to use a Q-tip (and a magnifying glass).
I’m trying to reach Suzanne Ashworth, who’s only a about a hundred miles from me. With any luck, she’ll want to adopt the plant and protect it from the hazards of my ignorance.
Thanks again for all the help!