This site's seed starting page already covers light requirements, timing, and hardening off before transplanting. This page covers what comes before and after that: deciding whether a crop should even be started indoors in the first place, saving seed that will actually grow true next season, testing whether old seed is still worth planting, and propagating plants from cuttings instead of seed entirely.
01 — Direct sow vs. transplant: matching the method to the crop
The decision comes down to root sensitivity and how much growing season a crop actually needs
Cornell University horticulture faculty frame this decision around a simple physical reality: some crops simply don't tolerate having their roots disturbed. Root vegetables, carrots, beets, and turnips, are grown specifically for that root, and transplanting typically damages or loses the taproot, leaving a plant with a weaker fibrous root system instead of the straight, well-formed root the harvest depends on. Corn, peas, and beans share a similar sensitivity for a different reason: their root systems establish quickly and dislike being moved once started, which is why these fast-growing crops are almost always direct-sown rather than started indoors.
On the other side of the decision are crops that need more growing season than many climates naturally provide. West Virginia University Extension notes that warm-season crops like tomatoes, peppers, eggplant, and melons require both a long time to reach maturity and soil temperatures too warm to reliably germinate outdoors early in the season; starting them indoors and transplanting after the danger of frost has passed effectively extends the growing season by six to eight weeks or more. A useful middle category exists too: crops like lettuce, broccoli, and cabbage generally tolerate either method well, and the choice often comes down to season and personal preference rather than a hard agronomic rule, cool spring soil favors starting lettuce as a transplant, while the same crop direct-sows just fine into the warmer soil of a late-summer planting for fall harvest.
- Direct-sow root vegetables (carrots, beets, radishes, turnips). Transplanting typically damages or shortens the taproot, which is the part being harvested.
- Direct-sow fast growers with sensitive roots (beans, peas, corn). These establish root systems quickly and generally dislike the disturbance of transplanting.
- Start warm-season, slow-maturing crops indoors (tomatoes, peppers, eggplant). WVU Extension notes this can effectively add six to eight weeks or more of usable growing season in climates where frost limits the calendar.
- Some crops genuinely work either way (lettuce, broccoli, cabbage). The better choice often depends on the season, cooler spring soil favors starting these as transplants, while warm late-summer soil supports direct sowing the same crop for a fall harvest.
02 — Seed saving basics: which seeds to save and how
Open-pollinated and heirloom varieties grow true from saved seed; hybrids do not
University of Minnesota Extension is direct about the single most important rule in seed saving: choose open-pollinated varieties rather than hybrids, since open-pollinated plants set seed that grows into plants very similar to the parent, while F1 hybrid seed does not breed true. An F1 hybrid is the deliberate first-generation cross of two distinct parent lines, bred specifically to combine selected traits; the seed that first-generation plant produces reverts unpredictably toward a mix of its grandparent lines rather than reproducing the hybrid itself. Heirlooms are simply open-pollinated varieties with a history, commonly defined as at least 50 years old and passed down through generations, but the practical rule that matters for seed saving is open-pollinated status itself, not age or heritage.
The mechanics of saving seed differ by crop type in ways worth knowing before harvest. UMN Extension recommends tomatoes, peppers, beans, and peas as the best crops for beginners, since their flowers are self-pollinating and need little special treatment. For tomatoes specifically, the process involves letting fruit ripen fully, then scooping the seeds and surrounding gel into a jar of water and letting the mixture ferment for about five days, stirring occasionally, until the seeds sink to the bottom; this fermentation breaks down a natural germination inhibitor coating the seed. Peppers are simpler still: allow fruit to ripen fully on the plant until it wrinkles, then remove and dry the seeds directly. In all cases, seeds need to dry thoroughly before storage, and should then be kept in a cool, dry, dark location, conditions extension guidance consistently identifies as the biggest factor in how long saved seed remains viable.
- Save from open-pollinated or heirloom varieties, never F1 hybrids. Hybrid seed does not breed true; the resulting plants are an unpredictable mix of the original cross's grandparent lines.
- Tomatoes, peppers, beans, and peas are the easiest crops for beginners. Self-pollinating flowers mean minimal risk of unwanted cross-pollination and little special seed treatment.
- Tomato seeds need fermentation before storage. Scoop seeds and gel into water, let ferment about five days until seeds sink, then rinse and dry; this removes a natural germination inhibitor.
- Dry seeds thoroughly, then store cool, dry, and dark. Storage conditions, more than seed age itself, are the biggest factor in how long saved seed stays viable.
03 — Testing old seeds for viability
A simple paper towel test reveals whether seed is worth planting before committing garden space to it
University of Illinois Extension's germination test method is a straightforward way to answer a question that otherwise requires guessing: place 10 seeds on a damp paper towel, fold or roll the towel, and seal it inside a plastic bag to hold in moisture. Label the bag with the date and seed type, then leave it somewhere warm, above 70°F, for the seed's typical germination period, generally 7 to 10 days if that figure isn't printed on the seed packet. Because exactly 10 seeds were used, the count of sprouted seeds converts directly into a germination percentage: 7 sprouted seeds means a 70 percent germination rate.
That 70 percent threshold is not arbitrary; it's the point extension guidance consistently treats as the practical cutoff for usable seed. Illinois Extension's guidance states that a 70 to 90 percent germination rate is still worth planting, just sown a bit more thickly than normal to compensate for the seeds that won't sprout, while a rate below 70 percent is generally a signal to replace the seed rather than gamble limited garden space and a full season's growing time on it. This test costs a few seeds and about a week's wait, a small trade against wasting an entire spring planting on seed that turns out to be mostly dead.
- Use exactly 10 seeds so the sprout count converts directly to a percentage. This is what makes the test simple to interpret without any additional math.
- Keep the sealed bag warm, above 70°F, for the seed's typical germination period. Most vegetable seeds show results within 7 to 10 days if a specific period isn't known.
- 70% or higher is good to plant, just sow a bit more thickly than normal. This compensates for the seeds that won't sprout without wasting garden space on a crop that's mostly not viable.
- Below 70%, it's generally worth replacing the seed. A poor germination rate risks an entire planting's worth of time and garden space on seed that's more likely to fail than succeed.
04 — Propagation from cuttings
Many herbs, berry bushes, and even some vegetables root readily from a healthy stem cutting
University of Missouri Extension guidance on herb propagation lays out the core technique: take cuttings from healthy, well-established plants during late spring or summer, cutting just below a node to form a 3 to 5 inch cutting, since fall cuttings root more slowly and healthy tip growth roots better than old woody stems. Most herbs root within two to four weeks under this method. Herbs in the mint family, rosemary, sage, thyme, oregano, lavender, and mint itself, propagate especially reliably this way, and soft-stemmed herbs like basil and mint typically root fastest in a jar of water, where root development is easy to watch directly, while woody-stemmed herbs like rosemary often do better rooted straight in soil, sometimes with rooting hormone to improve the odds.
Beyond herbs, a couple of vegetables propagate unconventionally well from cuttings rather than seed. Sweet potatoes don't grow from true seed the way most garden vegetables do; university and master gardener guidance describes starting a sweet potato tuber in moist soil or water until it produces rooted sprouts called slips, which are then twisted or cut free and planted as the actual crop. Tomatoes root readily from cuttings too, including the side-shoot "suckers" gardeners often prune away; a sucker of six or more inches, placed in a jar of water with lower leaves removed, typically develops its own roots within one to two weeks and can be planted out as a genuinely new, fruit-producing plant, a useful way to extend a short growing season or replace a plant lost partway through the year.
- Take herb cuttings in late spring or summer, cut just below a node, 3 to 5 inches long. University of Missouri Extension notes fall cuttings root more slowly, and healthy tip growth roots better than old woody stems.
- Soft herbs (basil, mint) root fastest in water; woody herbs (rosemary, sage) do better in soil. Water lets you watch root development directly; soil, sometimes with rooting hormone, suits woody stems better.
- Sweet potatoes propagate from slips, not true seed. A tuber rooted in moist soil or water produces sprouts (slips) that are removed and planted as the actual crop.
- Tomato suckers root readily in water within one to two weeks. A six-inch-plus sucker, with lower leaves removed, can become a genuinely new fruit-producing plant, useful for extending a short season or replacing a lost plant.
Quick reference
- Direct-sow root vegetables and fast growers with sensitive roots (carrots, beans, peas, corn). Start warm-season, slow-maturing crops indoors (tomatoes, peppers, eggplant). Some crops (lettuce, broccoli) work either way depending on season.
- Save seed only from open-pollinated or heirloom varieties, never F1 hybrids. Tomatoes, peppers, beans, and peas are easiest. Ferment tomato seeds ~5 days before drying and storing cool, dry, dark.
- Test old seed: 10 seeds on a damp paper towel, sealed in a bag, kept above 70°F for 7-10 days. 70%+ germination is plantable; below that, replace the seed.
- Herbs (especially the mint family) root well from cuttings in 2-4 weeks. Sweet potatoes propagate from slips, not seed. Tomato suckers root in water within 1-2 weeks and become new plants.
Primary sources
- Cornell University, School of Integrative Plant Science: Transplants or Direct Seeding, What's Best?: the root-sensitivity reasoning behind direct sowing root vegetables and fast growers.
- West Virginia University Extension: Using Transplants in the Garden: the warm-season crop transplanting rationale and the germination test method reference.
- University of Minnesota Extension: Saving Vegetable Seeds: the open-pollinated versus hybrid seed-saving rule and the tomato fermentation and pepper drying methods.
- University of Illinois Extension: Are My Seeds Still Good? Testing Seed Germination: the 10-seed paper towel test method and the 70% viability threshold.
- University of Missouri Extension: Growing Herbs at Home: the herb cutting technique, node placement, cutting length, and rooting timeline.
- Piedmont Master Gardeners: How to Grow Your Own Sweet Potato Slips: the sweet potato slip propagation process.