Which crops to start with, how far to isolate them, wet and dry processing, saving biennials through a Michigan winter, and how long the seed lasts. Written by Chris Izworski from the garden at Freighter View Farms in Bay City.
Saving your own seed is how gardeners worked for ten thousand years before seed came in a rack at the store, and it is still the cheapest, most durable thing you can do in a garden. Save seed from your best heirloom tomato and you get that same tomato next year, and the year after, adapted a little more to your soil each season. But seed saving has one rule that trips up beginners: some crops make it effortless, and some make it genuinely hard. The trick is knowing which is which before you start, so your first saved seed grows into the plant you expected rather than a surprise.
This is the table that should come first in every seed saving guide and rarely does. The self-pollinating crops at the top are nearly foolproof: their flowers pollinate themselves before they even open, so the seed comes true with almost no effort and almost no isolation. The insect and wind-pollinated crops below them cross with any other variety of the same species in range, sometimes a mile or more away, and the biennials will not even flower until their second year. Begin at the green end. A saved-seed habit built on tomatoes, beans, peas, and lettuce succeeds; one that starts with squash and carrots usually ends in disappointment.
| Difficulty | Crop | Pollination | Minimum isolation | Recommended isolation | Note |
|---|---|---|---|---|---|
| Easy | Tomatoes | Self-pollinating | 10 ft | 25 to 50 ft | The classic starter seed; wet process |
| Easy | Beans (bush and pole) | Self-pollinating | 10 ft | 25 ft | Dry in the pod on the plant |
| Easy | Peas | Self-pollinating | 10 ft | 25 ft | Dry in the pod on the plant |
| Easy | Lettuce | Self-pollinating | 12 ft | 25 ft | Let a few plants bolt and go to seed |
| Moderate | Peppers | Insect and self | 300 ft | 500 to 1,000 ft | Easy to process, but sweet and hot cross readily |
| Moderate | Sunflowers | Insect-pollinated | 500 ft | 1,000 ft | One variety at a time is simplest |
| Moderate | Zinnias | Insect-pollinated | 300 ft | 500 ft | Let heads dry on the stalk |
| Moderate | Calendula | Insect-pollinated | 200 ft | 500 ft | Self-sows freely once established |
| Advanced | Cucumbers | Insect-pollinated | 500 ft | 1,000 ft | Wet process; needs real isolation or hand-pollination |
| Advanced | Squash and pumpkins (C. pepo) | Insect-pollinated | 500 ft | 1,500 ft | Species cross wildly; hand-pollinate to be sure |
| Advanced | Winter squash (C. maxima) | Insect-pollinated | 500 ft | 1,500 ft | Isolate by species, not just variety |
| Advanced | Melons | Insect-pollinated | 500 ft | 1,500 ft | Warm-season, insect-crossed, demanding |
| Advanced | Corn | Wind-pollinated | 600 ft | 1,200 to 2,000 ft | Wind carries pollen far; needs many plants and distance |
| Advanced (biennial) | Kale and cabbage (Brassica) | Insect-pollinated | 1,000 ft | 1 mile | Second-year seeder; whole species intercrosses |
| Advanced (biennial) | Carrots | Insect-pollinated | 1 mile | 2 miles | Crosses with wild Queen Anne's lace |
| Advanced (biennial) | Beets and chard | Wind-pollinated | 1 mile | 5 miles | Wind-borne pollen travels for miles |
| Advanced | Spinach | Wind-pollinated | 1 mile | 5 miles | Wind-pollinated and quick to bolt |
| Advanced (biennial) | Onions | Insect-pollinated | 1,000 ft | 1 mile | Second-year seeder; short seed life after |
Isolation distance is the space to another variety of the same crop. Two tomato varieties ten feet apart stay nearly pure; two squash varieties of the same species need a quarter mile, or a paper bag and a paintbrush. If a neighbor grows the same crop, their planting counts too.
Nearly all seed saving comes down to one of two methods, decided by how the seed grows on the plant.
These crops carry their seed in wet flesh, and the seed has to be cleaned out of it. Scoop seeds and pulp into a jar, add a splash of water, and let it ferment on the counter for two to four days until a film of mold forms on top. That fermentation is not neglect, it is the point: it dissolves the gel coating that otherwise keeps the seed from germinating, and it kills several seed-borne diseases. When the mold has formed, pour off the top layer along with the pulp and any seeds that float, since good seed sinks. Rinse what is left until it is clean, spread it on a plate or a screen, and dry it fully for one to two weeks before storing. Skip paper towels, which the seed glues itself to permanently.
These crops dry their seed right on the plant, and your job is mostly patience. Leave bean and pea pods on the vine until they rattle and the pods are papery, past the point you would ever eat them. Let lettuce and flower heads dry on the stalk until the seed pulls free easily. Then bring them in, thresh the seed out by hand or by rubbing the pods, and winnow away the chaff by pouring the mix between two bowls in front of a fan so the light debris blows off and the heavy seed falls. Finish the drying indoors for a week before storage.
Carrots, beets, cabbage, kale, onions, and parsley are biennials: they grow a root or a head the first year and only flower and set seed the second. In a warm climate you leave them in the ground over winter and collect seed the next summer. In Zone 5 and 6 Michigan, a hard winter will kill many of them in place, so saving biennial seed here takes an extra step. Either heavily mulch the best plants in fall and gamble on a mild winter, or lift the roots before the ground freezes, store them in damp sand in a root cellar or a refrigerator near freezing, and replant them in spring to flower. It is real work, which is why most Michigan seed savers stick to annuals and buy fresh biennial seed. If you do try it, carrots deserve a warning: they cross with the wild Queen Anne's lace growing in every roadside ditch in this state, so roadside carrots and garden carrots are the same species and will mingle freely.
More saved seed dies in storage than from any crossing mistake, and the killers are moisture and heat. Seed must be bone dry before it goes into anything airtight, or it molds; a good test is that a properly dry bean shatters rather than dents when you hit it, and a dry seed snaps instead of bending. Michigan's humid late summer works against you here, so finish drying indoors in a room with moving air rather than in the garden. Once dry, the storage rule is simple and the reverse of a refrigerator's job: cool, dark, and above all dry. An airtight jar with a packet of silica gel or a spoonful of dry powdered milk in a twist of tissue, kept in the coldest, driest cabinet you have, will hold most seed for years. The old seed-saver's shorthand is that the storage temperature in Fahrenheit plus the humidity percentage should stay under 100.
Label everything the moment you store it, because dry seed is anonymous and a year is a long time. Variety, and the year saved, at minimum. The viability table below tells you how many seasons that seed stays worth planting.
Every year in storage costs some germination. The figures below are realistic lifespans in good, cool, dry storage; seed kept warm or damp fades far faster. When in doubt, run a germination test before the season: fold ten seeds into a damp paper towel, keep it warm, and count how many sprout in a week or two. Seven of ten means plant normally; three of ten means sow thickly or start fresh.
| Crop | Realistic viability | Storage method |
|---|---|---|
| Cucumbers | 5 to 7 years | Airtight container, cool and dark |
| Tomatoes | 4 to 6 years | Airtight container, cool and dark |
| Squash and melons | 4 to 6 years | Airtight container, dry |
| Zinnias | 3 to 5 years | Airtight container |
| Beans | 3 to 4 years | Paper envelope inside an airtight jar |
| Peas | 3 to 4 years | Paper envelope inside an airtight jar |
| Carrots | 3 to 4 years | Airtight, cool and dry |
| Lettuce | 2 to 3 years | Airtight, refrigerated |
| Peppers | 2 to 3 years | Airtight, refrigerated |
| Corn | 2 to 3 years | Airtight, low humidity essential |
| Parsley | 2 to 3 years | Airtight container |
| Sunflower | 2 to 3 years | Airtight, cool location |
| Onions | 1 to 2 years | Short-lived; sow next season |
| Term | What it means |
|---|---|
| Heirloom | An open-pollinated variety in cultivation for at least 50 years, usually with a documented history |
| Open-pollinated (OP) | Pollinated by natural means, wind or insects; the seed breeds true to the parent |
| Hybrid (F1) | A cross of two distinct parent lines; the seed does not breed true, so saving it gives you a grab bag |
| Isolation distance | The space between two varieties of the same crop needed to keep them from crossing |
| Roguing | Pulling off-type or weak plants before they flower, so only the best plants set the seed you save |
| Selfing | A plant pollinating itself, which is why self-pollinators like tomatoes and beans stay pure so easily |
| Biennial | A crop that grows leaves or roots the first year and only flowers and sets seed in its second |
You can save it, but it will not come true. An F1 hybrid is a cross of two parent lines, and its seed scatters into a mix of the grandparents, most of them worse than the hybrid you started with. Save seed only from open-pollinated and heirloom varieties. The seed packet will say if a variety is a hybrid.
Tomatoes, beans, peas, and lettuce, in that order. All four are self-pollinating, so they come true with next to no isolation, and between them they cover the wet process, the dry process, and letting a plant bolt. Master those and the rest of the table opens up.
For pure seed, yes, but there is a shortcut: hand-pollination. Bag a squash or cucumber flower before it opens, transfer pollen yourself with a small brush the next morning, and re-bag it, and you get pure seed from a single plant in a crowded garden. It is how serious savers keep varieties true on a small lot.
Use the Michigan planting calendar to time the indoor start and the seed starting guide for the lights and heat. Saving the seed is half the loop; starting it well is the other half.