Saving Seeds True-to-Type
How to Avoid Cross-Pollination
Plants which can be cross-pollinated by similar varieties are still easy to save if only one variety of the same species is grown at a time (e.g., one eggplant or one pepper). If using this method, however, make sure your neighbors aren't growing different varieties of the same plant, and that wild varieties of your plants do not grow in the local area. Queen Anne's Lace is the same species as the common carrot, for instance, and will cross-pollinate your carrots—carrots you grow from the resulting seeds will not grow true to the variety you started with.
'Isolate' Seed Plants for Genetic Purity
If you want to grow more than one crossable variety of a species at a time and save genetically pure seed from any of them, you can prevent crossing by 'isolating' your heirloom varieties from each other. Isolation means to prevent pollen from different varieties being able to reach each other and cross-pollinating (i.e., mixing) the varieties.
There are several ways to isolate heirloom varieties which will be discussed in detail below:
An excellent resource for learning more about techniques for protecting seed crops is Suzanne Ashworth's excellent book Seed to Seed, available from Seed Savers Exchange, an excellent resource for all seed savers.
Distance Isolation
The simplest way to isolate varieties is to plant them far enough away from each other so that cross-pollination is not possible (see Plant Isolation Distances). The amount of space needed for safe distance isolation varies for different plants—and there is always the risk that someone nearby may grow a cross-pollinating variety, so get to know your gardening neighbors!
Some plants can be protected from crossing by just a small distance, such as lettuces (25 feet between varieties) and eggplants (50 feet). Others, such as peppers, stretch the possibility of distance-isolation in the average garden by requiring 500 feet for safe isolation between varieties. Bee-pollinated plants such as the cabbage family (collards, broccoli, etc.), squashes and okra require from ¼ to 1 mile for complete safety—often difficult to accomplish or verify, due to gardening neighbors. Corn, a wind-pollinated plant, can require a mile or more for safe distance isolation and members of the Beet Family may need as many as 5 miles!
- plant the varieties far enough apart so that their pollen can't reach each other;
- grow each variety in separate, screened cages;
- cover individual flowers with bags;
- time plantings so that different varieties are not flowering at the same time, and so cannot pollinate each other.
Seed to Seed
An excellent resource for learning more about techniques for protecting seed crops is Suzanne Ashworth's excellent book Seed to Seed, available from Seed Savers Exchange, an excellent resource for all seed savers.
Distance Isolation
The simplest way to isolate varieties is to plant them far enough away from each other so that cross-pollination is not possible (see Plant Isolation Distances). The amount of space needed for safe distance isolation varies for different plants—and there is always the risk that someone nearby may grow a cross-pollinating variety, so get to know your gardening neighbors!
Some plants can be protected from crossing by just a small distance, such as lettuces (25 feet between varieties) and eggplants (50 feet). Others, such as peppers, stretch the possibility of distance-isolation in the average garden by requiring 500 feet for safe isolation between varieties. Bee-pollinated plants such as the cabbage family (collards, broccoli, etc.), squashes and okra require from ¼ to 1 mile for complete safety—often difficult to accomplish or verify, due to gardening neighbors. Corn, a wind-pollinated plant, can require a mile or more for safe distance isolation and members of the Beet Family may need as many as 5 miles!
Many Factors Affect Distance Isolation
The exact distance you'll need to safely isolate a particular crop depends on a number of factors. Central among these are the type of plant and how it is pollinated (i.e., wind, insects, self—or a combination of these). Also important are the particulars of your growing situation including exposure, climate, prevailing wind patterns and surrounding terrain and vegetation features.
Small Plantings More Sensitive to Crossing
Relative size of plantings has an impact, too. Small plantings are more vulnerable to foreign pollen (whether carried by wind or insects) than large plantings, since in a large planting foreign pollen is spread among many more plants. Further, plants on the edge of a group are more vulnerable to crossing than plants in the middle. For this reason, whenever a variety is important, collect seed from plants nearest the center of a planting for greatest purity.
These and many other factors help account for differences between the distance-isolation figures given by Suzanne Ashworth in Seed to Seed and those given by the USDA or other authorities (see the Plant Isolation Distances Table). While the USDA figures are based on large plantings, Ms. Ashworth's figures are better-adapted to the scale of the home gardener.
Trust Your Own Experience
Actual distances which will work for you may have to be determined experimentally. Until you know that smaller distances are safe for your conditions and plant varieties, use the larger distances. Caution is especially important with rare or heirloom plants. If you experiment with smaller isolation distances, use common varieties instead of rare ones in case of accidental cross-pollination. Remember that once two varieties have crossed, their genes are inextricably mixed.
Wind Pollination and Distance Isolation
Distances needed for isolation of wind-pollinated plants varies with your conditions. Wind patterns and strength, existence of windbreaks, etc., all have an effect. Wind-pollinated plants grown in wooded, low-wind areas will need much less distance than the same plants grown in vast, open, windy areas, for instance.
Pollen from corn, which is relatively heavy, falls to the ground within a few paces in a quiet protected spot, but can travel half a mile or more in open, windy areas. Windbreaks are more effective for plants with heavy pollen like corn, than for plants with light pollen like beets or lamb's quarters.
Insect Pollination and Distance Isolation
Isolation distances needed by insect-pollinated plants varies according to what animal or insect is the pollinator, and on how plentiful local nectar and pollen sources are. In areas where nectar and pollen sources are plentiful, bees and other pollinators do not have to travel as far in their foraging as in sparsely-vegetated areas.
If bees are the pollinators, distances needed also depend on which hives collect from where within your local area. Bee hives are territorial and do not overlap foraging areas—plants in one hive's territory won't be bee-pollinated by plants in a neighboring hive's territory. For this reason, distances needed to isolate bee-pollinated plants in areas with plentiful, diverse vegetation may be a quarter-mile or less, whereas distances for the same plants in sparsely-vegetated areas might be a mile or more
Self Pollination and Distance Isolation
Self-pollinated garden plants' flowers include both male and female parts and are receptive to their own pollen. This allows them to fertilize themselves. Among self-pollinating plants, some are exclusively self-pollinated, whereas others can be fertilized either by themselves or by other plants of the same species.
Self-Pollinators That Need Protection
Self-pollinating plants whose flowers are open during the time pollination takes place (such as okra or peppers) can either fertilize themselves or be pollinated by other plants (and so they do need some protection from crossing). Since they will self-pollinate, however, they can be caged without worrying about letting insects into their cages to pollinate them.
If these types of plants are grown out of the wind where bumblebees can't reach them (i.e., in a greenhouse or coldframe, etc.), it will help to gently jiggle the plants a time or two per day to mimic the wind and bees. This helps to move the pollen around within their flowers.
Self-Pollinators That Need No Protection From Crossing
Self-pollinating plants which fertilize themselves before their flowers open (such as tomatoes and beans) are exclusively self-pollinating. These do not need to be isolated under normal circumstances, since by the time their flowers open they will have already pollinated themselves. These plants also benefit from being shaken if they are grown where wind and/or bumblebees cannot shake their flowers naturally.
Even plants whose flowers are closed during pollination, however, might cross-pollinate under certain circumstances.Self-pollinating flowers can be forced open by hungry insects in areas with few nectar or pollen sources, for instance. For these reasons even plants which do not normally cross-pollinate may benefit from protection from nearby varieties of the same species in deserts or other sparsely-vegetated regions, or if their purity is particularly important.
Time Isolation
When distance isolation is a problem, caging is too costly or troublesome, and you're only growing a couple varieties in a season, you can use 'time isolation' to prevent crossing. Time isolation works with any two varieties that shed pollen over a limited time and have sufficiently different rates of maturation (as usual, don't forget your gardening neighbors, who may be growing varieties that will cross with yours).
To use time isolation, plant two similar varieties at staggered times. If properly times, by the time the later of the two varieties is flowering, the earlier variety will already have finished flowering and will no longer be producing or receptive to pollen. Plant the earlier, faster-maturing crop a couple or three weeks before the later, slower-maturing one. If they are plants which flower over a short time, the two flowering periods may not overlap at all.
Even if the flowering periods of two crossable varieties overlap a little, time isolation may still be an option. The secret in this case is to manually prevent flowers from blooming on both varieties at once. Simply remove late flowers from the earlier-flowering variety (after seeds have been produced) so that the later crop can pollinate and set seed without being crossed. Remove flower buds well before they open, since some varieties open early in the morning. This method can work well with plants which produce seed over a long season, such as okra.
Caging
If safe isolation distances are not available and time isolation is not suited to the plant (as for basil with its long flowering period and numerous, small flowers), 'caging' or 'bagging' techniques can also be used to insure against crossing. In caging, plants are protected by cages covered with mesh or fabric. The weave of the covering must be small enough to prevent passage of insects or pollen (depending on whether the plant is insect or wind-pollinated, respectively). Bags over individual flowers or flower heads can be used for self or wind-pollinating plants. In this case the bags simply act as tiny 'cages'.
Actual distances which will work for you may have to be determined experimentally. Until you know that smaller distances are safe for your conditions and plant varieties, use the larger distances. Caution is especially important with rare or heirloom plants. If you experiment with smaller isolation distances, use common varieties instead of rare ones in case of accidental cross-pollination. Remember that once two varieties have crossed, their genes are inextricably mixed.
Wind Pollination and Distance Isolation
Distances needed for isolation of wind-pollinated plants varies with your conditions. Wind patterns and strength, existence of windbreaks, etc., all have an effect. Wind-pollinated plants grown in wooded, low-wind areas will need much less distance than the same plants grown in vast, open, windy areas, for instance.
Pollen from corn, which is relatively heavy, falls to the ground within a few paces in a quiet protected spot, but can travel half a mile or more in open, windy areas. Windbreaks are more effective for plants with heavy pollen like corn, than for plants with light pollen like beets or lamb's quarters.
Insect Pollination and Distance Isolation
Isolation distances needed by insect-pollinated plants varies according to what animal or insect is the pollinator, and on how plentiful local nectar and pollen sources are. In areas where nectar and pollen sources are plentiful, bees and other pollinators do not have to travel as far in their foraging as in sparsely-vegetated areas.
If bees are the pollinators, distances needed also depend on which hives collect from where within your local area. Bee hives are territorial and do not overlap foraging areas—plants in one hive's territory won't be bee-pollinated by plants in a neighboring hive's territory. For this reason, distances needed to isolate bee-pollinated plants in areas with plentiful, diverse vegetation may be a quarter-mile or less, whereas distances for the same plants in sparsely-vegetated areas might be a mile or more
Self Pollination and Distance Isolation
Self-pollinated garden plants' flowers include both male and female parts and are receptive to their own pollen. This allows them to fertilize themselves. Among self-pollinating plants, some are exclusively self-pollinated, whereas others can be fertilized either by themselves or by other plants of the same species.
Self-Pollinators That Need Protection
Self-pollinating plants whose flowers are open during the time pollination takes place (such as okra or peppers) can either fertilize themselves or be pollinated by other plants (and so they do need some protection from crossing). Since they will self-pollinate, however, they can be caged without worrying about letting insects into their cages to pollinate them.
If these types of plants are grown out of the wind where bumblebees can't reach them (i.e., in a greenhouse or coldframe, etc.), it will help to gently jiggle the plants a time or two per day to mimic the wind and bees. This helps to move the pollen around within their flowers.
Self-Pollinators That Need No Protection From Crossing
Self-pollinating plants which fertilize themselves before their flowers open (such as tomatoes and beans) are exclusively self-pollinating. These do not need to be isolated under normal circumstances, since by the time their flowers open they will have already pollinated themselves. These plants also benefit from being shaken if they are grown where wind and/or bumblebees cannot shake their flowers naturally.
Even plants whose flowers are closed during pollination, however, might cross-pollinate under certain circumstances.Self-pollinating flowers can be forced open by hungry insects in areas with few nectar or pollen sources, for instance. For these reasons even plants which do not normally cross-pollinate may benefit from protection from nearby varieties of the same species in deserts or other sparsely-vegetated regions, or if their purity is particularly important.
Time Isolation
When distance isolation is a problem, caging is too costly or troublesome, and you're only growing a couple varieties in a season, you can use 'time isolation' to prevent crossing. Time isolation works with any two varieties that shed pollen over a limited time and have sufficiently different rates of maturation (as usual, don't forget your gardening neighbors, who may be growing varieties that will cross with yours).
To use time isolation, plant two similar varieties at staggered times. If properly times, by the time the later of the two varieties is flowering, the earlier variety will already have finished flowering and will no longer be producing or receptive to pollen. Plant the earlier, faster-maturing crop a couple or three weeks before the later, slower-maturing one. If they are plants which flower over a short time, the two flowering periods may not overlap at all.
Even if the flowering periods of two crossable varieties overlap a little, time isolation may still be an option. The secret in this case is to manually prevent flowers from blooming on both varieties at once. Simply remove late flowers from the earlier-flowering variety (after seeds have been produced) so that the later crop can pollinate and set seed without being crossed. Remove flower buds well before they open, since some varieties open early in the morning. This method can work well with plants which produce seed over a long season, such as okra.
Caging
If safe isolation distances are not available and time isolation is not suited to the plant (as for basil with its long flowering period and numerous, small flowers), 'caging' or 'bagging' techniques can also be used to insure against crossing. In caging, plants are protected by cages covered with mesh or fabric. The weave of the covering must be small enough to prevent passage of insects or pollen (depending on whether the plant is insect or wind-pollinated, respectively). Bags over individual flowers or flower heads can be used for self or wind-pollinating plants. In this case the bags simply act as tiny 'cages'.
Insect Pollination and Caging
Cages covered with regular window screen are fine for keeping insects safely away from insect-pollinated plants. Use large frames which hold the mesh away from the plants inside them, so that insects cannot reach flowers that might otherwise press against the inside of close-fitting cages. Build the cages large enough for the plants at maturity, and place them over the plants as soon as they start to flower (remove any flowers which open before the cages are put into place).
Caging procedures vary according to whether your plants can self-pollinate (such as peppers), or whether they are insect-dependent and so actually require insects for pollination (such as squash or basil). If they are dependent on insects for pollination, 'alternate day caging' will have to be used.
Alternate-Day Caging
Insect-dependent plants—which actually require insects for pollination—must have their cages removed periodically so that insects can reach their flowers and pollinate them.
Plant two or three varieties and cover them with separate lightweight cages. Once every other day (for two varieties) or every three days (for three varieties), remove the cage from one variety (don't remove cages from any two varieties on the same day, and replace the removed cage in the evening).
This exposes a different variety to pollinating insects each day, and gives each variety a chance to be pollinated every two or three days. Remember, however, that even removing just one cage at a time can still allow crossing if your neighbors are growing plants that will cross yours.
Insect-pollinated plants which are also self pollinating can be left in their cages full time and will produce seed.
Insect-dependent plants—which actually require insects for pollination—must have their cages removed periodically so that insects can reach their flowers and pollinate them.
Plant two or three varieties and cover them with separate lightweight cages. Once every other day (for two varieties) or every three days (for three varieties), remove the cage from one variety (don't remove cages from any two varieties on the same day, and replace the removed cage in the evening).
This exposes a different variety to pollinating insects each day, and gives each variety a chance to be pollinated every two or three days. Remember, however, that even removing just one cage at a time can still allow crossing if your neighbors are growing plants that will cross yours.
Insect-pollinated plants which are also self pollinating can be left in their cages full time and will produce seed.
Wind Pollination and Caging
When using cages to protect wind-pollinated plants from crossing, cover the cages with a fine-weave fabric (such as spun polyester) that keeps pollen out but allows air and sunlight to pass. Grow as many plants as possible inside each cage for a large genetic base. Shake plants or cages daily to help distribute pollen inside the cages.
If the plants you're protecting are small and closely-planted, spun polyester or like material can simply be wrapped around the group and tied at the base to form a frameless 'cage'. Be sure to thoroughly seal the bottom of the bag with cotton, leaves or mulch, etc.
For certainty with the very light-pollened plants such as chard and beets, or other wind-pollinated plants if they're growing in close quarters, plastic or other wind-impermeable material may need to be used.
When using cages to protect wind-pollinated plants from crossing, cover the cages with a fine-weave fabric (such as spun polyester) that keeps pollen out but allows air and sunlight to pass. Grow as many plants as possible inside each cage for a large genetic base. Shake plants or cages daily to help distribute pollen inside the cages.
If the plants you're protecting are small and closely-planted, spun polyester or like material can simply be wrapped around the group and tied at the base to form a frameless 'cage'. Be sure to thoroughly seal the bottom of the bag with cotton, leaves or mulch, etc.
For certainty with the very light-pollened plants such as chard and beets, or other wind-pollinated plants if they're growing in close quarters, plastic or other wind-impermeable material may need to be used.
Bagging and Hand Pollination
If none of the above isolation techniques are practical for you, or you want to maintain a high degree of control over which plants pollinate each other, you can individually hand pollinate flowers or flower heads and enclose them in cloth or paper bags. This technique works well with large-flowered plants such as squash or daylilies.
For more detail on any and all of these techniques, see Suzanne Ashworth's book Seed to Seed.
Amaranth
Amaranthus spp.
Amaranth is self-pollinating, but will also cross-pollinate (possibly even between different species). Further, wild amaranths are common in most areas worldwide. Individual heads can be bagged to allow growing several varieties in proximity or to ensure that wild plants don't cross the plants you're growing. From ½ mile (green amaranths) to two miles (grain amaranths) are needed for reliable distance isolation.
Grain amaranths may need support to keep the plants from falling over as they mature because of their large, heavy seed heads. Collect the seed heads as they dry on the plants and store in closed paper bags to finish drying (many of the seeds will shed naturally).Don't let the seed heads get wet after they dry. Chaff easily blows away after seed heads are crumbled—watch for thorns or prickles in some plants!
If germination is slow, lightly stir the soil's surface... amaranth seeds need some sunlight after a period of darkness to germinate. This trait adapts them to disturbed or overturned soil, hence one of their common names, "pigweed," so-called because they would germinate in hordes in an area after pigs had passed and turned the soil, exposing their seeds to the light so they could germinate.
Cut seed heads when they are becoming dry and hang them upside-down in large paper bags or over tarps to collect the tiny seeds. The dried heads can easily be crumbled in the hands and the chaff gently blown away if you're in a hurry.
Amaranth seeds can last for many years if properly stored, and can sprout in the garden even after several years in the soil.
Arugula
Eruca sativa
Arugula is self-sterile—insects must be able to reach the flowers of different plants for pollination to occur. Different varieties of arugula will cross each other and must be separated by ½ mile for safe distance isolation. Arugula will not cross other members of the Cabbage Family.
To save seeds from arugula, leave plants in the ground to overwinter after harvesting leaves for eating during the growing season. As with any member of the Cabbage Family, allow seeds to ripen and dry on the plant in the spring—but do not leave for long after they are dry or the pods will shatter and the seeds disperse—arugula pods are thin-walled, and shatter quickly after drying.
This trait of readily throwing seed suggests that arugula may be recently domesticated, since long-domesticated plants tend to hold their seeds for a longer time after maturing Seeds from plants that release their seeds early failed to be collected and replanted when agriculture started, thus genetically favoring those plants which hold onto their seeds for a longer time after maturing.
Arugula seeds will last for 4 or more years if properly stored.
Basil
Ocimum basilicum
Basil relies on insects for pollination, but can be reliably isolated by as little as 150 feet since most of the pollinating insects are small and don't travel far. Different basil varieties will cross each other.
Harvest seed heads as they dry and allow to finish drying in a warm, dry spot. Seeds are easily removed by crumbling the dried flower heads and then blowing away the chaff. You can practice over a plastic sheet at first until you get the hang of it.
Plants cut back after harvest will grow another set of leaves for harvest—and even produce seeds again—if your season is long and hot. A branch or two of each plant can easily be left to go to seed while collecting leaves for cooking with from the rest of the plant.
Basil seeds will last up to 5 years if properly stored.
Beans
Phaseolus spp.
Beans are self-pollinated, and different bean varieties do not commonly cross-pollinate each other. Similarly colored varieties should be separated by enough distance to keep the vines from intertwining, to make them easy to distinguish at harvest. Allow pods to dry on the vines before picking and shelling, then finish drying the beans in a dry spot.
If you're eating your beans green, allow just one or two pods per plant to remain and mature for seed... too many pods maturing on an individual plant will cause it to stop setting more beans and concentrate on maturing the ones it has.
Pick beans for seed after the pods are ripe and have dried on the plants. Don't allow dried pods to get rained on as the beans may quickly mildew or sprout in their pods. When very dry many pods will split on their own to drop their seeds; the rest can be easily crumbled in the hands and the finer chaff blown away after removing the big pieces. Finish drying the beans in a dry spot indoors or under cover. Always use a innoculant when planting new bean seeds.
Bean seeds, properly dried and stored, will keep for 4 years.
Beets
Beta vulgaris
Beets and Swiss chard will cross-pollinate, as they are from the same species. Beets/chard must be separated by wind-proof caging, bagging or up to 2 to 5 miles of distance to ensure purity as their wind-blown pollen is exceedingly small and light.
It's easy to leave the base and center of chard plants to over-winter, flower and produce seeds while still eating plenty of leaves. However, to save seed from beets you'll have to plant 20 to 30 plants to leave in the ground to over-winter if you want to get seeds- which is very difficult in Hawaii even upcountry. But, in Climates that have a winter...getting a great seed is actually quite easy. You can harvest tasty beet greens for the first part of the season, and you can crowd the plants a bit. You don't have to pamper them with lots of room, water and fertilizers to get plenty of seeds in the spring—just make sure they're big enough to get through the winter and re-sprout.
Allow beet seeds to fully mature and become dry on the plants before harvesting. After final drying the seeds can be easily rubbed off the stems. Beet seeds will last for up to 5 years if properly stored.
Broccoli
Brassica oleracea
Insect-pollinated, biennial broccoli will cross, and must be isolated from, all other members of B. oleracea by one mile for reliable distance isolation (see Cabbage Family). Since broccoli plants are mostly self-infertile, they should be planted in groups of at least 10 or more plants to maintain a decent genetic base and seed viability.
Harvest central heads and some secondary shoots for eating, then leave a healthy side shoot or two on each plant to over-winter and flower for seeds.
Harvest seed pods before the pods split open naturally, but after they have fully matured and dried on the stalks—the seeds will not continue ripening after the plants or stems are cut. Finish drying upside-down in paper bags or hanging in bundles over a tarp. When the plants are completely dry, any seeds that haven't naturally fallen out of their seed pods are easily removed by crumbling the pods.
Broccoli seeds will last for 5 years if properly stored
Cabbage Family
Brassicaceae
Mostly self-infertile, bee-pollinated members of the Cabbage Family (Brassicaceae) require up to a mile for distance isolation. Members of the same species in the Cabbage Family will cross-pollinate, which presents a problem in species with many members. For instance collards, broccoli, Brussels sprouts, cauliflower, cabbage, kohlrabi and kale (except Siberian kale) are all Brassica oleracea and will cross each other. Brassica rapa includes all the turnips, Chinese mustards and Chinese cabbages. Different species within the Cabbage Family will not cross.
Brassicas are mostly biennial—they grow and mature in the first season, then over-winter before setting seed in spring of their second year. In colder areas where Brassicas don't make it through the winter (they're very hardy), they can be over-wintered in pots in the greenhouse and then transplanted into the garden in early spring to flower and produce seeds.
Since most Brassica seeds remain viable for four or more years, four varieties of a single species can be grown at a time and seed stocks maintained if only one variety is allowed to flower and set seed each year. Alternate-day caging is another option for isolating two or three crossable varieties at a time (the cages must be removed periodically to allow bees to pollinate the flowers... see Alternate-Day Caging).
Brassica seeds will not continue to ripen after harvesting, so allow them to mature and dry completely before removing them from the parent plants—but don't tarry, either. In many Brassicas the seed pods shatter and release their seeds just days after they have matured and dried, especially in hot, dry weather.
The Cabbage Family includes the following species:
Brassica juncea: mustard greens.
Brassica nigra: black mustard.
Brassica napus: rape, Siberian kale, rutabaga.
Brassica oleracea: broccoli, Brussels sprouts, cabbage, cauliflower, collards, kale.
Brassica rapa: turnip, Chinese cabbage, Chinese mustard.
Eruca sativa: arugula, roquette, rocket salad.
Raphanus sativus: radish, daikon.
Carrot Family
Umbelliferae
Self-sterile Umbelliferae (also known as the Carrot Family) are dependent on insects' bringing pollen from other plants for fertilization. Umbelliferae require up to 1 to 3 miles for reliable distance isolation. Members of different varieties within the same species will cross, but members of different species will not cross.
Bagging or caging can be used to separate varieties of the same species, in which case hand pollination is necessary. Use a soft-bristle brush to transfer pollen between umbels on different plants during the time the tiny individual flowers are blooming (up to 30 days per umbel).
Alternate-day caging can be used for growing two varieties of the same species without hand pollinating, if you are certain that no crossable wild or domesticated varieties of that species are growing within a mile or so—but whether any of your neighbors are growing different varieties of the same species (e.g., carrots and carrots, dill and dill, etc.) within a mile would be difficult to verify.
The Carrot Family includes the following species:
Apium graveolens: celery and celeriac.
Anethum graveolens: dill.
Anthriscus cerefolium: chervil.
Coriandrum sativum: coriander, cilantro.
Daucus carota: carrot.
Foeniculum vulgare: fennel.
Petroselinum crispum: parsley.
Collards
Brassica rapa
Insect-pollinated, biennial collards will cross other members of B. oleracea (see list in Cabbage Family) and needs 1 mile for safe distance isolation. Since collards are mostly self-infertile, they should be planted in groups of 10 or more plants, and some seed collected from each (healthy) plant.
Plants can be eaten from normally—just leave a few leaves in the fall to overwinter and make seeds in the spring.Let the seeds mature fully and pods dry on the plants before harvesting—but don't wait too long or the pods will shatter and you'll lose the seeds.
Collard seeds can last up to 4 years if properly stored.
Cilantro
Coriandrum sativum
Quick-to-bolt cilantro (or coriander) crosses with other cilantro varieties and can be safely isolated with ½ mile of separation between varieties. Allow seeds to dry completely on plants before harvesting.
Cilantro seeds will last for several years when properly stored.
Eggplant
Solanum melongena
Self-pollinating Eggplants can be safely isolated by 50 feet of separation.
Eggplants should be left on the plants until well past the eating stage before harvesting for seed. The eggplants will have gone past their normal, ripe color and become translucent and dry (usually a dull, unattractive whitish, yellowish, or brownish color).
It's a good idea to keep eggplants off the ground during ripening, since they may begin to rot when they rest on the ground. Clean seeds according to the wet-cleaning process outlined in Cleaning Wet Seeds.
Long-lasting eggplant seeds will remain viable for 5 or more years if properly stored.
Lettuce
Lactuca sativa
Lettuce is self-pollinating, but plants can cross under some circumstances. 25 feet of separation is generally sufficient to prevent crossing, however.
While each flower opens only during the morning of one day, the flowering period is long and there are almost always flowers blooming on the plants. This means that a flowering plant will have flowers and seeds in all stages of maturity.
Gather dried seed heads (they are easy to recognize) every couple or three days as they ripen and dry, or wait until most seed heads have dried and hang the plant upside down over a tarp or in a paper bag (harvest dry seeds if rains threaten).
Lettuce seeds can remain viable for 3 years if properly stored.
Onion
Allium cepa
Insect-pollinated Onion Family plants need up to 1 to 3 miles for safe isolation. Closely planted groups of plants can be caged or bagged and then hand-pollinated.
To hand-pollinate, remove covers and use a fine, light paintbrush to mimic the action of visiting insects, thoroughly mixing pollen between several flowers. Make sure to hand-pollinate the flowers during a time (such as early morning or late evening) when insects are not present, and replace covers quickly and securely.
Allow seeds to ripen and dry on the plants, then harvest quickly to avoid losing seeds. Onion seeds are short-lived and should only be stored for one or two years before planting.
Pumpkin
Cucurbita spp.
Pumpkins can belong to either C. maxima or C. pepo. Varieties within these species will cross each other, but C. maxima will not cross C. pepo. Find your pumpkins' species from the seed company where you purchase them, or look them up in Suzanne Ashworth's excellent seed saving resource, Seed to Seed.
Pumpkins produce wet seeds (see Cleaning Wet Seeds). Store fully-ripe pumpkins for 3 weeks after harvesting before removing and cleaning the seeds.
Pumpkin seeds, like those of other members of the Squash Family, benefit from fermenting after being removed from the fruit—see Why Ferment Some Seeds?.
Pumpkin seeds will keep for 5 or more years if properly stored.
Radish
Raphanus sativus
Radishes will cross other radishes including daikon, but not turnips (Brassica rapa) or other members of the Cabbage Family. Separate radish and daikon varieties from each other by ½ mile for safe distance isolation.
Pick pods after they dry completely on the plant. Pick every day or two, as the pods will break open naturally to release their seeds soon after drying.
Radish seeds can last 4 or 5 years if properly stored.
Squash Family
Cucurbitaceae
Bee-pollinated members of the Squash family (Cucurbitaceae), require up to a mile for distance isolation. Different species of Cucurbitaceae do not cross-pollinate, so one variety from each species can be grown together without danger of crossing. For instance, one variety of crookneck or zucchini (Cucurbita pepo), one butternut or acorn squash (Cucurbita moschata), one watermelon (Citrullus vulgaris), one cantaloupe or muskmelon (Cucumis melo), one luffa (Luffa aegyptiaca), a hard gourd (Lagenaria siceraria) and a cucumber (Cucumis sativus) could all be grown together without crossing each other.
Find out from your seed company which species your varieties belong to, or consult Suzanne Ashworth's Seed to Seed for a comprehensive listing of Cucurbitaceae varieties and the species to which each belongs (there are no reliable, general rules for non-botanists to determine species). Personally in Hawaii I like to only use seeds that have gone though a season on the islands- as I know that it is in their genetic memory to be able to withstand the heavy Hawaiian Rains, the bugs, and the humidity. My favorite varieties for Maui specifically are Kabocha Squash and the Tahitian Squash.
Insect-pollinated and are self-infertile, if Cucurbits are isolated by caging, bees must be allowed to reach and pollinate the different varieties on alternating days (see Caging).
Cucurbits can also easily be pollinated by hand (use pollen taken from the same variety). After hand-pollinating the flowers, replace the cages, or bag or tape individual flowers shut to prevent further pollination. For more detail, see Seed to Seed.
Squashes should be fully mature before harvesting—for summer and other soft squashes, this is well past the eating stage. Harvest when skins are hard and leathery. Melons should be fully ripe before they are picked, as some will not complete ripening of their seeds if they are picked too soon. Harvest melons only after the vine tendril nearest the individual melon in question has dried and withered, and wait another 3 weeks before opening the melon to harvest the seeds. Clean the seeds according to directions in Cleaning Wet Seeds.
Allow dry-seeded members of the Cucurbit family (i.e., gourds, luffa) to dry on the vines until the shells are dried and the seeds inside rattle if shaken. Open the gourd and clean the seeds by winnowing.
After harvesting wet-seeded Squash family fruits, store the unopened fruits for another 20 days before removing the seeds. This is because some squash family seeds gain in size and viability for 20 days after harvesting. After the 20 day waiting period has passed, cut the fruits open and remove the seeds to prepare them for storage.
Squash seeds can be fermented for higher germination and better disease-resistance (see Why Ferment Some Seeds?—don't ferment seeds if they appear to have already naturally fermented while waiting in the wet fruit, as evidenced by the smell and appearance of the seeds and pulp).
After fermentation, clean the seeds by pouring off pulp and dead seeds (seeds which will float are dead and should be discarded). Use the same cleaning directions as for tomato seeds (see Cleaning Wet Seeds). Whether you've fermented the seeds or not, rub them underwater between your fingers gently but thoroughly while cleaning them, to remove the naturally occurring gel from their coats. Dry the cleaned seeds on a shiny surface (they will stick to paper) until they are brittle, but—as always!—do not use heat.
The Squash Family includes the following species:
Citrullus vulgaris: watermelons, citrons.
Cucumis melo: muskmelons, cantaloupes, honeydews.
Cucumis sativus: cucumbers.
Cucurbita maxima: banana, buttercup, hubbard and turban squashes, some pumpkins.
Cucurbita mixta: cushaw (except golden) squashes.
Cucurbita moschata: butternut, golden cushaw and cheese squashes.
Cucurbita pepo: acorn, crookneck, scallop, spaghetti and zucchini squashes, small striped and warty ornamental gourds, some pumpkins.
Lagenaria siceraria: hard-shelled gourds.
Luffa acutangula: angled luffas.
Luffa aegyptiaca: smooth luffas.
Sechium edule: chayotes.
Sunflower
Helianthus spp.
Insect-pollinated sunflowers need from ½ to 3 miles for isolation. Wild sunflowers—which will cross most cultivated varieties—are very common, making reliable distance isolation difficult at best. Uncommon species (such as Silver-Leaf Sunflower, H. argyophyllus) can probably be grown without danger of crossing, but most varieties will require bagging or caging for certain isolation. Caging is not practical for most sunflowers because of their size.
Since some varieties are self-infertile and have to be pollinated by pollen from other plants, caged or bagged sunflowers should be hand pollinated. Once a day while florets are blooming (one to two weeks per head), unbag two heads at a time and gently rub them together or use a soft-bristle paint brush to transfer pollen from one head to another. Hand pollinate a different pair of heads each time if possible. Rebag seed heads promptly after pollinating to keep insects from interfering.
Allow sunflower heads to dry on the plants before harvesting whole heads and hanging them upside-down in a protected spot to complete drying. The seeds can then be removed from the heads by vigorous rubbing. Store and plant the seeds in their kernels for protection.
Sunflower seeds can be kept for 5 or more years if properly stored.
Swiss Chard
Betula vulgaris
Swiss chard and beets are wind-pollinated and in the same species. All varieties of beets and Swiss chard will cross each other. Different varieties must be caged, bagged or separated by up to 5 miles for safe distance isolation.
Let seeds mature and dry on the stalk before harvesting, the complete drying before gently rubbing the seeds off their stalks. Each 'seed' is botanically a berry, and contains several actual seeds (breaking them apart would damage many of the seeds). This is why chard and beets often come up several plants to a spot despite the most carefully-frugal sowing efforts.
Chard seeds will last for up to 5 years if properly stored.
Tomatoes
Lycopersicon lycopersicum
Almost all modern tomatoes can be safely grown without isolation and will not cross—'currant' tomatoes (such as Cherry Tomatoes), and 'potato-leafed' tomatoes (such as Brandywine) are possible exceptions and may cross other currant or potato-leaf varieties. Grow as many standard tomatoes as desired, but grow only one currant tomato or one potato-leaf tomato at a time to ensure purity (or cage them, or separate varieties by 500 feet). Currant and potato-leaf tomatoes will not usually cross with common tomato varieties. My personal inclination for Hawaii outdoor gardening is to plant cherry, Roma and Mid-sized Tomatoes only. Beefsteak and Brandywine tomatoes tend to too easily get stung outdoors and then create more pest issues then they are worth.
It's best to not plant all a valuable variety's seeds in one season until you are sure it doesn't cross with any other varieties you grow.
Allow tomatoes to ripen thoroughly on their vines to at least the eating stage before harvesting them to collect their seeds. Upon harvesting, tomato seeds are best fermented in order to remove a germination-inhibiting gel which covers the seeds, and to kill diseases. In nature, fermentation of fallen ripe fruits removes this gel, and this process is imitated when preparing tomato seeds. See Fermenting Seeds and follow the directions.
If fermenting tomato seeds seems too much trouble, they will still germinate if the slippery gel surrounding the seeds is carefully rubbed off while you're cleaning them. Seeds treated this way will germinate, but they will not have had the protection of the fermentation process killing disease organisms. If you noticed any problems with your plants (leaves spotting or dying, inexplicable wilting, etc.), the extra trouble of fermentation will be well worth the effort.
Dry your tomato seeds on a piece of glass or a shiny plate—the wet seeds will stick to paper and be difficult to remove without damaging them.
Tomato seeds will store safely for 4 or more years after being properly dried and stored.
So- That is a brief introduction to Seed Saving. For me, Seed Saving is one of the most Sacred, Empowering acts that we can do in working closely with the land. This is my form of a stock-market...ensuring that I have saved everything I need to ensure that myself, my friends and my family can eat for years in the future. I encourage everyone to try this year to save at least one seed that can be passed down...and I promise you will not regret it.
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