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Seed saving is great way to save some money on your vegetable garden by keeping back some of the seeds from your garden to save for the next year. It's also a way to preserve heirloom seed varieties as well as to save seeds from plants that have adapted to growing in your own unique growing environment. Since plants can sometimes cross-pollinate, though, it's important to know whether or not you need to do anything to try to prevent cross-pollination and to know which vegetables you need to isolate for seed saving and which ones you don't need to worry about isolating.
The Basics of Seed Saving
When you are saving seeds, you are letting some of your vegetable crop grow to maturity so that it will produce seeds. This might mean letting some plants grow past the point where you would normally want to harvest them (like with green beans, cucumbers, etc.) You want the vegetables to be fully ripe and sometimes that might mean letting them ripen more than you would usually want to for that particular plant. Then, once the plant has gone to seed you will harvest the seeds. This process can vary based on which type of vegetable you are growing and wanting to use for seed saving. And then the final step would be to let those seeds dry out and then label them and save them for the next year. I described this process in a bit more detail in a previous article about how to save seeds from your garden.
It's also important to note that if you are trying to save seeds and you want to be able to grow the same variety that is true to type the following year then you need to save seeds from heirloom, open-pollinated plants. If you save seeds from a hybrid plant then you will end up with a mystery variety and you might not end up with the same characteristics as the plant that you were saving seeds from. You might end up with vegetables that have a different size, shape, or color, and the taste could be effected, too. So, if you don't mind experimenting, it could be fun to save seeds from a hybrid variety to see what you end up with, but if you want something reliable and you want to know how your plants will turn out then it's best to stick to saving seeds from heirloom, open-pollinated plants.
Before you actually save seeds, though, the first thing to figure out is whether or not you need to isolate any of your plants. Depending on what you are growing and where you are growing it you might not even need to worry about isolating any plants.
Considerations for Deciding If You Need to Isolate Your Plants
Do You Live Near Any Other Farms or Gardens?
If your garden is on land where there aren't any other surrounding farms or if you live in a suburban neighborhood where none of your nearby neighbors grow a garden then you might not have to worry about isolating your plants from neighbors in order to save seeds from them, and you would need to think about only the potential for cross-pollination with the plants in your own garden.
If you do live near a farm or near a neighbor who has a garden, though, then it will depend on how far away your garden is and also what types of vegetables you are growing. Some vegetables don't need very much space between them for isolation distances, but other vegetables can be cross-pollinated even from larger distances. (This chart from Seed Savers Exchange is a great resource for isolation distances that you need for different types of vegetables.)
The larger distance requirement is especially true of wind-pollinated vegetables like corn. If you live near any corn fields or near anywhere that corn might be growing then it will be harder to avoid cross-pollination if you are trying to grow corn yourself. One method you could try is to time your planting so that your corn isn't maturing at the same time as the other corn growing nearby. You could either try to grow a different variety of corn that would mature at a different time or you could wait a couple of weeks and plant your corn later after your neighbor's corn was planted.
Are You Growing More Than One Variety of a Vegetable?
If you are growing only one variety of a vegetable then you wouldn't need to worry about isolating your plants unless you live near someone else who is also growing that same type of vegetable like we talked about above. If you wanted to grow two different varieties of a particular vegetable, though, then you would need to isolate them to save seeds if you wanted to preserve the same variety otherwise the two kinds might end up crossing. For example, if the only type of cucumber you wanted to grow was the Boston Pickling variety then you wouldn't need to worry about isolating your cucumber plants. But if you wanted to grow both the Boston Pickling and Marketmore varieties of cucumbers then you would need to consider some type of isolation for saving seeds from those plants to avoid cross-pollination.
And if you are growing plants in the squash family there is a extra factor to consider because within the squash family there are also subgroups (Moschata, Maxima, and Pepo, and then Argyrosperma which is a less common one). Varieties within each of these subgroups are less likely to cross with one another, but it is possible that it could happen. Just like with the self-fertile plants, if you weren't overly concerned about keeping your seeds 100 percent pure, you could grow one type of squash of each of those varieties without worrying too much about them cross pollinating (unless you live close to someone who is also growing winter squash, of course.) So if you were growing a variety of winter squash in the Maxima family then you could also grow one in the Pepo family, and it would be less likely for cross-pollination to occur. You can find out if your squash variety is a Maxima, Moschata, or a Pepo by looking at the information on the seed packet or by researching it online.
How Are Your Plants Pollinated?
Depending on what type of vegetable you are growing, your plants might be insect-pollinated, wind-pollinated, or self-pollinated.
Some common insect-pollinated vegetables are:
- Squash
- Cucumber
- Melons
- Radishes
Some common wind-pollinated vegetables are:
- Corn
- Spinach
Some common self-pollinated vegetables are:
- Beans
- Peas
- Tomatoes
- Peppers
Self-pollinated vegetables don't usually need to be isolated unless you want to be really careful to avoid cross-contamination. So if it was really important for you to preserve a specific variety (like if you had a family heirloom variety that isn't easy to find anywhere else, for example, or if you were trying to sell seeds from your plants), then it would make sense to use some isolation techniques. But otherwise you usually don't have to worry about isolating the self-pollinated plants. It's possible for cross-pollination to happen (I've had it happen with beans before), but it's not very likely.
There's another category of vegetables that's a bit different, though, and those are the biennial plants. Some plants (including most root vegetables and also cabbage) need two years to produce seeds. So for those plants you would actually need to harvest the root of the plant at the end of the season (which would mean digging up a carrot and saving the whole carrot for example). And then the following year you would plant the carrot and wait for it to produce a flower and then form seeds. You can read more about the seed saving process for biennial plants here.
For these biennial plants you wouldn't need to worry about isolating the plants while they are growing in their first year because they aren't producing flowers yet that would be pollinated. The time when you would have to think about isolating them is in the second year when you are re-planting the roots in the ground and when flowers will grow and produce seeds.
Some common biennial plants are:
- Carrots
- Beets
- Parsnips
- Turnips
- Onions
- Cabbage and other Brassica family plants
How to Figure Out If You Need to Isolate Your Plants
Here are a couple of different examples of what it might look like to decide whether or not to isolate your plants for seed-saving.
Example 1: Tomatoes
You live in a suburban town and you know that none of your next door neighbors are growing any tomato plants in their yards. You are also growing just one variety of tomato, Brandywine. This means that you don't need to worry about doing anything to isolate the flowers on your tomato plant and you can save seeds from them without worrying about cross-pollination.
If, however, you decided that you wanted to grow three different varieties of tomato plants, then you would have a choice to make. Since tomato plants are self-pollinating, it's less likely that you would have to deal with crossing, but if it was really important for you to make sure that none of your plants cross-pollinated then you would either need to separate those varieties farther apart in your garden (by at least 10 feet according to this chart from Seed Savers Exchange) or your would need to use something like a blossom bag to isolate the individual flowers on the plants.
Example 2: Winter Squash
You are growing some Delicata winter squash and it's the only type of squash that you are growing in your garden, but you live right next door to a small farm that grows several types of winter squash. In this case you would probably want to isolate your plants with a physical barrier to be on the safe side since insects could travel from the plants on the farm over to your plants. One way to do that would be to use some netting over your plants or a blossom bag over each flower that you want to isolate. You could also try tying the flowers shut with some string so the bees and other insects can't get inside to access the pollen. You would also need to hand pollinate those flowers yourself since the insects wouldn't have access to them anymore, and you would need to isolate both male and female flowers so the pollen wouldn't be mixed with any other pollen from neighboring plants. This article describes the hand-pollination process in more detail.
How to Isolate Your Plants
I mentioned a couple of the different methods already, but two of the biggest ways to isolate your plants are by distance and by using some type of physical barrier. For distance, you would need to use a different distance based on which type of vegetable your are growing, using a chart like the one from Seed Savers to see how many feet you need to have in between your plants.
For physical barriers you could use something like insect netting to drape over your plants or use individual blossom bags to cover the flowers. This article from Seed Savers Exchange goes into more detail about all of the different isolation methods that you can use to make sure you avoid cross-pollination in your garden.
(Lori Elliott is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for us to earn fees by linking to Amazon.com and affiliated sites.)
The information in this post is not to be taken as medical advice and is not intended to diagnose or treat any disease.