1. Introduction — Seed Saving Is Genetic Insurance

The commercial seed supply is narrower than it appears. Four companies control over 60% of global proprietary seed sales. The varieties they sell are selected for shipping durability, uniform ripening, and mechanical harvest compatibility — not flavor, nutrient density, or regional adaptation. When a variety stops selling in sufficient volume, it gets dropped from catalogs. No announcement. No archive. It simply vanishes.

Heirloom varieties survive only as long as someone keeps growing and saving them. Every open-pollinated variety in existence today persists because an unbroken chain of growers — sometimes spanning centuries — saved seed from one harvest and planted it the next season. Break that chain and the variety is gone. No corporation will maintain it. No government program will rescue it.

This is not sentimentality about old tomatoes. Genetic diversity is functional insurance. Monoculture fails when conditions change. The Irish Potato Famine killed a million people not because potatoes are fragile but because an entire country planted a single variety — the Irish Lumper — and Phytophthora infestans found no resistance anywhere in the gene pool. Diverse open-pollinated populations contain the raw genetic variation that allows adaptation. Removing that variation removes the capacity to respond to new diseases, new climates, and new growing conditions.

Seed saving is also economic independence. A single packet of heirloom tomato seeds costs $3–5. One healthy tomato contains enough seed to plant an acre. Over a lifetime of gardening, the math is not subtle. More importantly, saved seed adapts. Each generation grown in your soil, your climate, and your microbiome drifts genetically toward fitness in that specific environment. After 5–7 generations, locally saved seed outperforms catalog seed of the same variety because natural selection has been working on it the entire time.

The skills are not difficult. They are specific. This guide covers every step from understanding pollination biology to long-term frozen storage, with enough detail that a first-year gardener can start saving seed from easy crops immediately and work up to the more demanding species as confidence builds.

2. Open-Pollinated vs. Hybrid vs. GMO — Why It Matters for Seed Saving

Open-Pollinated (OP)

Open-pollinated varieties produce offspring genetically identical (or very close) to the parent. They have been stabilized through many generations of selection — the genetic dice have already been rolled thousands of times and the population has settled into a consistent expression. When you save seed from an OP tomato, the next generation looks, tastes, and grows like the parent. This is the only category suitable for seed saving.

The term "heirloom" is a subset of open-pollinated. It generally refers to OP varieties that predate the hybrid seed era (roughly pre-1950), though the exact cutoff is debated and ultimately irrelevant. What matters is genetic stability and true-to-type reproduction.

F1 Hybrids

F1 hybrids are the first-generation cross between two distinct inbred parent lines. The parents are selected for complementary traits, and the cross produces offspring that express "hybrid vigor" — often larger, more uniform, and higher-yielding than either parent. This is real. Hybrid vigor is a documented genetic phenomenon (heterosis).

The problem for seed savers: F1 hybrids do not breed true. Their genetic makeup is heterozygous — they carry hidden recessive traits from both parent lines. When F1 plants reproduce, those traits segregate unpredictably in the F2 generation. You get a chaotic mix of sizes, shapes, colors, flavors, and growth habits. Some plants may resemble one grandparent, some the other, some neither. The uniformity of the F1 generation is a one-time trick.

This is not a conspiracy. It is Mendelian genetics. But it does mean that saving seed from hybrid varieties is a waste of garden space unless you are deliberately breeding — a multi-year project requiring isolation, selection, and stabilization over 6–8 generations minimum.

Seed packets labeled "F1" or "hybrid" should be avoided for seed saving purposes. If the packet does not specify, and the variety name includes a trademark symbol or patent notice, it is almost certainly a hybrid.

GMO (Genetically Modified Organisms)

GMO seed contains laboratory-inserted genes from unrelated organisms — bacterial genes for insect resistance (Bt), viral promoter sequences for herbicide tolerance (Roundup Ready), etc. These modifications cannot occur through natural breeding. GMO seed is patented. Saving it is illegal under most licensing agreements, and the traits themselves are designed for industrial monoculture systems incompatible with regenerative growing.

GMO varieties are not available through home garden seed catalogs. They are sold exclusively to commercial agricultural operations under technology use agreements. For the seed saver, the relevant point is simple: source your seed from reputable heirloom and open-pollinated suppliers. If a variety is sold by a small independent seed company without a technology agreement, it is not GMO.

3. Pollination — Understanding What Crosses and What Doesn't

The single most important concept in seed saving is pollination control. If pollen from a different variety reaches your seed crop, the resulting seed will be a cross — not true to type. Understanding which crops self-pollinate and which cross-pollinate determines how much effort isolation requires.

Self-Pollinating Crops

Self-pollinating plants have "perfect" flowers — each flower contains both male (anther) and female (stigma) parts, and pollination occurs before the flower fully opens. The pollen travels millimeters, not meters. These are the easiest crops for beginner seed savers because accidental crossing is rare.

Primary self-pollinators: Tomatoes, peppers (mild crossing possible), beans, peas, lettuce, endive, wheat, barley, oats, rice.

Even self-pollinators can occasionally cross. Tomatoes in hot climates (above 90°F) extend their stigmas beyond the anther cone, allowing insect-mediated crossing. Peppers are visited by small bees that transfer pollen between flowers. The crossing rate is low — typically 2–5% — but if genetic purity matters, provide 10–25 feet of separation or a physical barrier.

Cross-Pollinating Crops

Cross-pollinating plants require pollen from a different individual. Some have separate male and female flowers (squash, corn). Others have self-incompatibility mechanisms that reject their own pollen (many brassicas, apples). These crops will cross readily with other varieties of the same species, and isolation is mandatory for true-to-type seed.

Key concept: Crossing occurs within a species, not between different crops. Butternut squash (Cucurbita moschata) will cross with other C. moschata varieties but not with zucchini (C. pepo) or Hubbard squash (C. maxima). Knowing the species designations prevents unnecessary isolation.

Isolation Distances by Species

Crop Species Pollination Type Minimum Isolation Distance Notes
Tomato Solanum lycopersicum Self 10–25 ft Increase to 50 ft in hot climates
Pepper Capsicum annuum Self (with insect crossing) 50–300 ft Hot peppers cross readily with sweet
Bean (common) Phaseolus vulgaris Self 10–20 ft Very low crossing rate
Pea Pisum sativum Self 10–20 ft Nearly zero crossing
Lettuce Lactuca sativa Self 10–20 ft Flowers tiny, rarely cross
Squash (summer) Cucurbita pepo Cross (insect) 1/4–1/2 mile Or hand-pollinate
Squash (butternut) Cucurbita moschata Cross (insect) 1/4–1/2 mile Different species than C. pepo
Squash (Hubbard) Cucurbita maxima Cross (insect) 1/4–1/2 mile Different species than C. pepo
Cucumber Cucumis sativus Cross (insect) 1/4–1/2 mile Or hand-pollinate
Melon Cucumis melo Cross (insect) 1/4–1/2 mile Watermelon is different species
Corn Zea mays Cross (wind) 1/2–1 mile Or stagger planting by 3 weeks
Carrot Daucus carota Cross (insect) 1/4–1/2 mile Crosses with wild Queen Anne's lace
Onion Allium cepa Cross (insect) 1/2–1 mile Strong insect pollination
Beet Beta vulgaris Cross (wind) 1/2–1 mile Crosses with Swiss chard (same species)
Cabbage/Broccoli/Kale Brassica oleracea Cross (insect) 1/4–1 mile All B. oleracea cross with each other
Turnip/Chinese cabbage Brassica rapa Cross (insect) 1/4–1 mile All B. rapa cross with each other
Radish Raphanus sativus Cross (insect) 1/4–1/2 mile Crosses with wild radish
Spinach Spinacia oleracea Cross (wind) 1/4–1/2 mile Dioecious — separate male/female plants
Sunflower Helianthus annuus Cross (insect) 1/2–1 mile Strong bee attraction

Hand Pollination as an Alternative

For cross-pollinating crops in small gardens, hand pollination eliminates the need for isolation distance. The technique varies by crop but follows a consistent pattern: identify unopened female flowers the evening before they open, tape or bag them shut, transfer pollen from a male flower of the desired variety the next morning, then re-seal the female flower and mark it. The resulting fruit contains true-to-type seed regardless of what else is flowering nearby.

Squash is the easiest crop to hand-pollinate because the flowers are large and the male/female distinction is obvious (males have a straight stem, females have a small fruit at the base). Corn is the hardest because pollen is airborne and silk must be bagged before any pollen arrives.

4. Wet-Processed Seeds — Fermentation Extraction

Wet-processing applies to seeds embedded in moist fruit flesh. The primary crops: tomatoes, cucumbers, melons, and some squash. The fermentation step is not optional — it removes germination-inhibiting compounds from the seed coat, kills several seed-borne diseases, and separates viable seed from pulp and non-viable seed.

Tomato Seed Saving (The Benchmark Method)

Step 1: Select fruit. Choose fully ripe fruit from your best plant (see Section 7 for selection criteria). Let the fruit ripen on the vine to full maturity — slightly overripe is better than underripe for seed purposes.

Step 2: Extract seeds. Cut the tomato horizontally (across the equator, not stem to blossom). Squeeze the gel and seeds into a glass jar or plastic container. Add 1–2 tablespoons of water if the mixture is very thick.

Step 3: Ferment. Cover the container loosely (cheesecloth, paper towel, or the lid set on top without sealing). Place in a warm location (70–85°F). Fermentation takes 2–4 days depending on temperature. The surface will develop a layer of white or gray mold — this is correct. The fermentation process breaks down the gelatinous seed coat that contains germination inhibitors and kills many seed-borne pathogens including bacterial speck, bacterial canker, and early blight.

Step 4: Monitor timing. Ferment until the mold layer covers the surface and the mixture smells sour (like vinegar, not like rot). Do not over-ferment. If seeds begin to sprout in the jar, you have waited too long. Two to three days is typical at room temperature.

Step 5: Separate viable seed. Add water to the jar — roughly double the volume. Stir vigorously. Viable seeds are heavy and sink. Pulp, mold, and non-viable (empty) seeds float. Pour off the floating material. Repeat 2–3 times until the water runs clear and only clean seeds remain at the bottom.

Step 6: Dry. Spread seeds in a single layer on a ceramic plate, glass dish, or parchment paper. Do not use paper towels — seeds stick permanently. Do not use paper plates — seeds absorb moisture back from the paper. Dry in a well-ventilated area out of direct sunlight. Stir seeds once or twice daily to prevent clumping. Seeds are dry enough for storage when they snap cleanly instead of bending — typically 5–7 days at room temperature.

Cucumber and Melon

Same fermentation process with one critical difference: the fruit must be left on the vine well past eating maturity. An eating-ripe cucumber is harvested green and immature — the seeds inside are not viable. For seed saving, leave cucumbers on the vine until they turn yellow or orange and the skin hardens. Melons should be fully ripe and slightly overripe — soft spots and strong fragrance indicate mature seed.

Scoop seeds, ferment 2–3 days, rinse, and dry on a hard surface. Melon seeds are large enough that clumping is rarely an issue. Cucumber seeds may need manual separation during drying.

5. Dry-Processed Seeds — Thresh and Winnow

Dry processing applies to seeds that mature inside dry pods, husks, or seed heads. The crops: beans, peas, grains, lettuce, most herbs, and most flowers. No fermentation is needed. The process is mechanical: dry the plant material, separate seed from chaff, and clean.

Beans and Peas

Harvest timing. Leave pods on the plant until they are brown, dry, and papery. The seeds inside should rattle when you shake the pod. If frost threatens before pods are fully dry, pull the entire plant and hang it upside down in a dry, ventilated space to finish curing.

Threshing. For small quantities, shell pods by hand. For larger harvests, place dried pods in a pillowcase or cloth bag and beat against a hard surface — a table edge, a wall, a clean floor. The pods shatter and release seed.

Winnowing. Pour the seed/chaff mixture from one container to another in front of a gentle breeze (a box fan on low works indoors). Chaff blows away; heavy seed falls into the receiving container. Repeat until clean.

Lettuce

Lettuce goes to seed readily in heat — the process is called bolting. Allow the seed stalk to grow until fluffy seed heads form (similar to dandelion puffs). Each tiny seed has a parachute-like pappus attached.

Harvest timing. Seeds ripen over 2–3 weeks, not all at once. Harvest daily by shaking the seed head over a paper bag or bucket, or cut the entire stalk when roughly half the seeds show white fluff and hang upside down inside a paper bag. The remaining seeds will mature and drop into the bag.

Cleaning. Rub the dried seed heads between your palms over a bowl. Winnow to remove pappus and stem fragments. Lettuce seed is small — a #20 mesh screen (0.033 inch / 0.84mm openings) catches debris while passing seed through, or vice versa depending on the debris size.

Flowers and Herbs

Most flower and herb seeds mature in visible seed heads or capsules. The general approach: allow seed heads to dry on the plant until they begin to shatter, then cut and collect.

Basil, oregano, thyme, sage: Seed heads dry on the stem. Cut when seeds are dark and hard. Strip seeds by running dried flower stalks through your closed fist over a bowl. Winnow.

Marigold, zinnia, sunflower, echinacea: Large seed heads are hand-harvested. Marigold and zinnia seeds are pulled directly from the dried flower base. Sunflower heads are dried whole and seeds rubbed out by hand or with a stiff brush.

Calendula, dill, fennel, coriander: Seeds shatter easily once dry. Harvest slightly early (when seeds begin to brown but before full shattering) and finish drying in a bag.

6. Biennials — The Two-Year Seed Crops

Biennial crops complete their life cycle over two growing seasons. Year one: they grow vegetative structure (root, leaves, bulb). Year two: they flower, set seed, and die. This means seed saving from biennials requires overwintering the plant — either in the ground or in storage — and growing it through its second season.

Carrots (Daucus carota)

Year 1: Grow carrots normally. In fall, select the best roots (see Section 7). Dig them carefully.

Overwintering — Mild climates (Zone 7+): Mulch heavily (6–8 inches of straw) and leave roots in the ground. They survive winter and send up flower stalks in spring.

Overwintering — Cold climates (Zone 6 and below): Dig roots in late fall. Cut tops to 1 inch — do not cut into the crown. Pack in slightly damp sand or sawdust in a root cellar, unheated garage, or refrigerator. Target: 32–40°F, 90–95% humidity. Replant in spring as soon as soil can be worked, spacing 12–18 inches apart.

Year 2: Flower stalks emerge in late spring. Large compound umbels of tiny white flowers attract numerous pollinators. Carrot flowers cross-pollinate via insects and will cross with Queen Anne's lace (wild carrot, same species). Isolation distance: 1/4 to 1/2 mile, or cage with exclusion netting and introduce flies as pollinators.

Seed harvest: Seeds ripen from the outside of the umbel inward. Harvest when the outermost seeds are brown and dry but before they shatter. Cut the seed head, dry in a paper bag for 1–2 weeks, then rub to separate seed from stem. Winnow to clean.

Beets and Swiss Chard (Beta vulgaris)

Same species — they will cross with each other. Grow only one variety of beet/chard for seed each season unless using isolation.

Overwintering: Same as carrots. Beet roots store well in cold, damp sand. Replant in spring 12 inches apart.

Year 2: Beets send up tall (3–5 ft) flower stalks with dense clusters of small green flowers. Wind-pollinated — isolation distance: 1/2 to 1 mile.

Seed harvest: Seeds form in corky clusters along the flower stalk. Cut stalks when clusters are brown and dry. Strip seeds by hand. No winnowing needed — the clusters are the seed (each cluster contains 2–4 seeds).

Onions (Allium cepa)

Overwintering: Select firm, disease-free bulbs of ideal size and shape. Store in mesh bags at 35–45°F. Replant in early spring 6 inches apart, 2 inches deep.

Year 2: Flower stalks reach 3–4 feet. Large spherical umbels of white or pink flowers are strongly attractive to bees. Cross-pollination is heavy — isolate varieties by 1/2 to 1 mile, or cage with introduced pollinators.

Seed harvest: Seeds are small, black, and angular. Harvest when seed capsules begin to split open and black seeds are visible. Cut the entire flower head into a paper bag. Dry for 2 weeks. Shake to release seeds. Winnow to remove capsule fragments.

Cabbage, Broccoli, Kale, Brussels Sprouts, Kohlrabi, Cauliflower (Brassica oleracea)

All of these are the same species. Every one of them will cross with every other one. Growing cabbage and kale for seed in the same season without extreme isolation produces useless hybrid seed.

Overwintering: In mild climates, most B. oleracea varieties overwinter in the ground with mulch protection. In cold climates, dig the entire plant (with root ball) and store in a root cellar. Replant in spring.

Year 2: Yellow four-petaled flowers on branching stalks. Insect-pollinated. Seeds form in long thin pods called siliques. Harvest when pods are dry and brown but before they shatter. Dry whole stalks upside down in paper bags. Thresh by crushing pods. Winnow to clean. Seeds are small, round, dark brown to black.

7. Selection Criteria — Choosing Which Plants Earn Seed-Saving Status

Saving seed from the wrong plants degrades a variety just as effectively as cross-pollination does. Selection is the seed saver's most powerful tool — it is the same mechanism that created every domesticated crop in existence. Choose deliberately and the variety improves with each generation. Choose randomly and it drifts.

What to Select For

Vigor. The plant should be among the healthiest in the row — strong stem, deep green foliage, robust root system. A plant that struggles to grow will produce seed that struggles to grow.

Disease resistance. If one plant in a row survives a disease outbreak that flattens its neighbors, that plant's seed carries whatever genetic resistance made the difference. This is the most valuable selection pressure available to a home seed saver.

True-to-type characteristics. The plant should match the expected description of the variety — fruit shape, color, size, leaf form, growth habit. Off-type individuals (throwbacks, mutations, or unintended crosses) should be removed before flowering if possible.

Earliness vs. late maturity. Depends on your goal. Selecting the earliest-maturing plants shifts the variety toward shorter season adaptation — useful for northern growers. Selecting late-maturing plants may produce larger yields or better storage qualities.

Flavor and intended use. Taste the fruit before saving seed. A tomato that looks perfect but tastes bland is selecting for blandness.

What Not to Save From

The last fruit on the vine. It survived because nothing else wanted it. Late-season fruit from stressed plants produces inferior seed.

The first plant to bolt. For crops where bolting is undesirable (lettuce, spinach, beets, cilantro), saving seed from early bolters selects for a bolt-prone population. Rogue out early bolters and save from the last plants to bolt.

A single plant. Minimum population sizes matter for maintaining genetic diversity within a variety. Save from at least 5–6 plants for self-pollinating crops and 20–50 plants for cross-pollinating crops. Saving from a single plant every year creates a genetic bottleneck that increases inbreeding depression.

Minimum Population Sizes for Genetic Maintenance

Crop Type Minimum Plants for Seed Saving Ideal Population
Self-pollinating (tomato, bean, pea) 5–6 20+
Cross-pollinating, insect (squash, carrot, onion) 20–30 50–100
Cross-pollinating, wind (corn, beet, spinach) 50–100 200+

8. Drying and Cleaning — Preparing Seed for Storage

Improper drying is the most common cause of seed failure in home seed saving. Seeds that feel dry to the touch may still contain 12–15% moisture — enough to support fungal growth in storage and enough to kill embryos if frozen.

Target Moisture Content

For room-temperature storage: Below 8%. At this level, most storage fungi cannot colonize the seed.

For freezer storage: Below 6%. Water inside seed cells expands when frozen. If moisture content is above 8%, ice crystal formation ruptures cell membranes and kills the embryo. Seeds must be thoroughly dried before freezing.

The snap test: Bend a seed. If it bends, it is too wet. If it snaps cleanly, it is at or below 8% moisture. This is a rough field test but surprisingly reliable for most medium to large seeds.

Air Drying

Spread seeds in a single layer on a hard, non-porous surface — ceramic plates, glass, parchment paper, or fine mesh screens. Avoid paper towels (seeds stick), cardboard (absorbs unevenly), and newspaper (ink transfer).

Ideal drying conditions: 70–85°F, 20–40% relative humidity, good air circulation. Do not use direct sunlight — UV damages seed embryos. Do not use an oven — even low heat (above 95°F) kills seeds of most species.

Drying time varies by seed size: lettuce and tomato seeds dry in 5–7 days. Bean and squash seeds may take 2–3 weeks. Corn kernels are among the slowest — allow 4–6 weeks of air drying.

Desiccant Drying

For seeds destined for freezer storage, desiccant drying achieves lower moisture content than air drying alone.

Method: Place dry seeds in a sealed container with an equal weight of fresh silica gel (indicating type — the beads turn pink when saturated). Seal the container. After 7 days, the silica gel will have pulled seed moisture down to approximately 5–6%. Remove seeds and immediately transfer to final storage containers.

Recharging silica gel: Spread saturated (pink) silica gel on a baking sheet and dry in an oven at 250°F for 2 hours. Beads return to blue/orange indicating color and can be reused indefinitely.

Cleaning Screens

For large-volume seed cleaning, a set of graduated mesh screens separates seed from debris by size.

Screen Mesh Size Opening (inches) Use
1/4 inch 0.250 Pre-screen large debris from corn, beans
#6 0.132 Clean large seeds (beans, squash, corn)
#10 0.079 Clean medium seeds (pepper, cucumber, melon)
#14 0.056 Clean small-medium seeds (tomato, eggplant)
#20 0.033 Clean small seeds (lettuce, carrot, basil)
#30 0.023 Clean very small seeds (oregano, thyme, celery)

Two screens used together — one that passes the seed and catches debris, one that catches the seed and passes dust — handle most cleaning tasks.

9. Storage — Temperature, Moisture, and the Viability Equation

Seed storage is applied physics. Two variables control everything: temperature and moisture. The relationship is quantified in Harrington's Rule of Thumb: for every 1% decrease in seed moisture content (within the 5–14% range), storage life doubles. For every 10°F decrease in storage temperature, storage life doubles again. These effects are multiplicative.

A practical example: tomato seed at 12% moisture stored at 75°F lasts roughly 3–4 years. Dry it to 6% moisture (3 doublings = 8x) and cool it to 0°F (roughly 7.5 doublings for the 75°F drop = ~180x). Theoretical storage life: centuries. In practice, 20–30 years of high viability is realistic with proper drying and freezing.

Room Temperature Storage

Acceptable for seeds that will be planted within 1–3 years. Requirements:

  • Moisture content below 8%
  • Airtight containers — glass jars with rubber-sealed lids, mylar bags with heat seals, or zip-seal bags with air squeezed out
  • Cool, dark, dry location — a closet interior, not a kitchen or garage
  • Add a small desiccant packet (silica gel) to each container as moisture insurance
  • Temperature ideally below 70°F, never above 80°F

Refrigerator Storage (35–40°F)

Doubles to triples storage life compared to room temperature. Same preparation requirements. Use airtight containers to prevent seeds from absorbing refrigerator humidity (which is typically high). Allow containers to reach room temperature before opening to prevent condensation on cold seeds.

Freezer Storage (0°F / -18°C)

The gold standard for long-term preservation. Requirements are strict:

Step 1: Dry seeds thoroughly by air drying followed by 7 days with desiccant (see Section 8). Moisture must be below 6%.

Step 2: Package in airtight, moisture-proof containers. Glass jars (leave headspace), vacuum-sealed mylar pouches, or vacuum-sealed mason jars with a FoodSaver adapter all work. Standard zip-seal bags are not adequate — they allow slow moisture migration.

Step 3: Freeze. Seeds tolerate repeated freeze-thaw cycles poorly. Package in small quantities so you can remove only what you need for a planting season without thawing the entire stock.

Step 4: When retrieving seeds, allow the sealed container to warm to room temperature before opening. Opening a frozen container in warm air causes condensation on the cold seed — instantly raising moisture content and potentially triggering premature germination or fungal growth.

Vacuum Sealing

Vacuum sealing removes oxygen, which slows lipid oxidation — a significant cause of viability loss in oil-rich seeds (sunflower, corn, brassicas). Combine vacuum sealing with desiccant drying and freezer storage for maximum longevity.

Caution: Vacuum pressure can crush fragile or thin-shelled seeds. Place delicate seeds in a rigid container (small glass jar) inside the vacuum bag, or use a vacuum jar attachment instead of bag sealing.

Germination Testing

Test seed viability before planting, especially for seed older than 2 years or seed of uncertain storage history.

Method: Place 10 seeds (or 20 for better statistical accuracy) on a damp paper towel. Fold the towel over the seeds. Place in a zip-seal bag, partially sealed to allow gas exchange. Keep at 70–80°F. Check daily. Count germinated seeds at the expected germination time for that species (usually 5–14 days).

Interpreting results: 80–100% germination = excellent viability, plant at normal rate. 60–80% = still usable, plant thicker to compensate. Below 50% = seed is declining, use immediately or discard. Below 30% = not worth planting.

10. Seed Viability Table — Expected Storage Life by Species

All figures assume properly dried seed (below 8% moisture) stored in sealed containers at cool room temperature (60–70°F). Freezer storage extends all figures by 2–5x.

Crop Expected Viability (Years) Notes
Vegetables
Artichoke 5–7
Arugula 4–5
Asparagus 3 Low viability; plant fresh
Bean (snap/dry) 3–4 Larger seeds lose viability faster in humid conditions
Beet 4–5 Seed clusters may contain multiple embryos
Broccoli 3–5
Brussels sprouts 4–5
Cabbage 4–5
Carrot 3 Among the shortest-lived vegetable seeds
Cauliflower 4–5
Celery 3–5
Collards 5
Corn (sweet) 1–2 Very short-lived; high oil content degrades quickly
Corn (dent/flint) 3–5 Better storage than sweet corn
Cucumber 5–7 One of the longest-lived vegetable seeds
Eggplant 4–5
Endive 5–7
Kale 4–5
Kohlrabi 3–5
Leek 2–3 Short-lived; save fresh seed frequently
Lettuce 3–5
Melon 5–7 Seeds improve with 1–2 years of age (reduced vine vigor)
Mustard greens 4
Okra 2–3
Onion 1–2 Shortest-lived common vegetable seed; save every year
Parsley 1–3
Parsnip 1–2 Use only fresh seed; viability drops sharply
Pea 3–4
Pepper 2–4
Pumpkin 4–6
Radish 4–5
Rutabaga 4–5
Spinach 3–5
Squash (summer) 4–6
Squash (winter) 4–6
Swiss chard 4–5 Same species as beet
Tomato 4–7 Among the most durable vegetable seeds
Turnip 4–5
Watermelon 4–5
Herbs
Basil 5–8 Exceptionally long-lived
Chamomile 3–4
Chive 1–2 Short-lived; save frequently
Cilantro/Coriander 5–7
Dill 3–5
Fennel 3–4
Lavender 3–5 Low germination rate even when fresh (40–60%)
Lemon balm 3–4
Oregano 3–4
Parsley 1–3 Listed above; same viability
Rosemary 2–3 Difficult from seed; cuttings preferred
Sage 2–3
Thyme 3–4

11. Sources

  • Ashworth, S. (2002). Seed to Seed: Seed Saving and Growing Techniques for Vegetable Gardeners. Seed Savers Exchange.
  • Bubel, N. (1988). The New Seed Starter's Handbook. Rodale Press.
  • Ceccarelli, S. (1994). Specific adaptation and breeding for marginal conditions. Euphytica, 77, 205–219.
  • Deppe, C. (2000). Breed Your Own Vegetable Varieties: The Gardener's and Farmer's Guide to Plant Breeding and Seed Saving. Chelsea Green Publishing.
  • Fowler, C. & Mooney, P. (1990). Shattering: Food, Politics, and the Loss of Genetic Diversity. University of Arizona Press.
  • Harrington, J.F. (1972). Seed storage and longevity. In T.T. Kozlowski (Ed.), Seed Biology (Vol. 3, pp. 145–245). Academic Press.
  • Justice, O.L. & Bass, L.N. (1978). Principles and Practices of Seed Storage. USDA Agriculture Handbook 506.
  • McCormack, J.H. (2004). Seed Processing and Storage: Principles and Practices of Seed Harvesting, Processing, and Storage. Saving Our Seeds.
  • Navazio, J. (2012). The Organic Seed Grower: A Farmer's Guide to Vegetable Seed Production. Chelsea Green Publishing.
  • Westengen, O.T., Jeppson, S., & Guarino, L. (2013). Global ex-situ crop diversity conservation and the Svalbard Global Seed Vault: Assessing the current status. PLOS ONE, 8(5), e64146.