Start seeds, buy transplants and plant them out
Reading a seed packet, testing old seed, starting seeds indoors under lights, choosing transplants, hardening them off and planting them out.
Start here Essentials
This module asks you to get each crop into the garden or pot the way it usually goes in: from seed, or as a transplant you buy or grow. Everything marked Go deeper is optional on a first pass.
- Choose seed or transplant for each crop. Use the usual-start table. If your weekly hours are short, buying transplants for the transplanted crops is a sound first-season choice. Direct sowing or transplanting.
- Read each packet. Note whether days to maturity count from seed or from transplant, plus the sowing depth, spacing and packed-for year. Read the packet.
- Buy stocky transplants that are not flowering, and harden them off for 7 to 14 days: short and shaded at first, and indoors whenever it falls below 45 °F. Hardening off.
- Plant out on the calendar date, adjusted for this year's soil and weather. Water the plant first, set it at the depth it grew, and water it in.
- Sow direct crops at the packet's depth, thin to the final spacing, and log each date in the season log.
Minimum time: about 30 minutes to plan, then the planting itself. Done when: your first crop is in the ground or the pot.
1. Read the packet before you sow Understand
A seed packet is a short technical sheet. It tells you how deep to sow, how far apart, how long the seed takes to sprout, how long the crop takes to reach harvest, and which season the seed was packed for. Most first-season sowing mistakes are packet details that went unread: seed buried too deep, rows sown too thick, a long-season variety started too late.
Montana State University Extension's planting guide lists what a packet usually carries: the type of vegetable, days to maturity, sowing instructions, spacing in the row and between rows, seeding depth, thinning or transplanting notes, germination information, the year the seed was packaged for, and notes from the seed company. Penn State Extension's Pike County Master Gardeners give a similar checklist written as questions: start indoors or sow directly, days to germinate, days to harvest, sowing depth, when to move seedlings outdoors, spacing, and the expiration date. The two lists agree on substance. Use either as the checklist for every packet you buy.
Days to maturity
Days to maturity is the length of time from the day seeds or transplants go into the garden to the first harvest. Montana State's guide defines it that way and adds two qualifications worth keeping in mind. Convention It is an average, and actual time varies with growing conditions. A cool spring, a shaded bed or a dry stretch all lengthen it.
The definition hides a trap. For crops usually set out as transplants, such as tomato, pepper and eggplant, the figure on the packet is usually counted from the day the transplant goes into the garden, not from the day the seed was sown indoors. Colorado State University Extension's planting guide marks its days-to-harvest figures for those crops with a T for that reason: its tomato figure of 65 days is counted from transplanting. A tomato seed sown indoors needs another 5 to 7 weeks before it is a transplant. If you read 65 days as the time from seed to harvest, you plan a season that is six weeks too short.
For crops sown directly in the garden, such as beans, carrots and radishes, the count starts on the day of sowing. When a packet does not say which it means, assume transplant timing for the crops usually transplanted and seed timing for the crops usually sown directly, and check the seed company's catalog description if it matters for your season. It matters most in short seasons, which is the case the fall formula in Module 6 handles.
Days to maturity is also the number you compare between varieties. Two tomato varieties can differ by three or four weeks. In a short season that difference decides whether a crop fits at all; the Lindqvist example later in this module turns on exactly that.
Depth, spacing and the packed-for year
Sowing depth on a packet is specific to the crop. Where a packet gives none, Utah State University Extension's seed-starting fact sheet gives the common rule: Convention sow at a depth of about 2 to 3 times the seed's diameter. Tiny seeds such as lettuce sit barely covered; a bean seed goes about an inch down. University of Minnesota Extension's planting guide adds that seeds can go a little deeper in sandy soil than in clay, because sand dries faster at the surface and clay crusts over a deep seed.
Spacing has two numbers on most packets: the distance to sow seeds and the distance to thin plants to. The first is closer, because not every seed comes up. The second is what the grown plant needs. Module 5 uses equidistant spacing for planning beds; the packet's thinning distance is the variety-specific check on that plan.
The packed-for year (sometimes a "sell by" or expiration date) tells you the season the seed company tested the lot for. It starts the clock on viability, which is the next section's subject.
Seed storage, viability and the germination test
A seed is alive. It is a dormant embryo with a food supply, slowly using that supply up. Viability is the ability of a seed to germinate and grow into a normal seedling. Physical principle It declines with time, and it declines faster in warm, humid storage. Nebraska Extension's publication on seed storage (G2090) says longevity depends mainly on storage temperature, relative humidity and the moisture in the seed itself, and that seed kept longer than a year needs extra care to keep germination high. The practical rule is to store packets cool and dry, in a closed container away from a stove, a sunny window or a damp basement.
Published viability years, and why two sources differ Go deeper
Extension services publish the number of years seed of each crop typically stays usable in good storage. Nebraska's G2090 and University of Wisconsin-Madison Extension's Dane County page on testing seed viability both publish such lists. For most crops in this course they agree. For four they do not.
| Crop | Nebraska G2090 | Wisconsin (Dane County) |
|---|---|---|
| Onion | 1 | 1 |
| Pepper | 2 | 2 |
| Sweet corn | 2 | 2 |
| Bean, pea, carrot | 3 | 3 |
| Tomato | 3 | 4 |
| Broccoli | 3 | 5 |
| Spinach | 3 | 5 |
| Beet, squash | 4 | 4 |
| Cabbage | 4 | 5 |
| Eggplant, kale | 4 | not listed |
| Lettuce, radish, cucumber | 5 | 5 |
We show both rather than averaging them. Convention These are averages for well-stored seed, compiled by different offices from different references. Neither describes your packet. A two-year-old tomato packet that sat in a hot garage may be weaker than a four-year-old packet kept in a cool closet. The course's crop guide uses Nebraska's figures and notes Wisconsin's where they differ. Treat a listed year as the point at which testing becomes worth the trouble, not as a date when the seed dies.
The paper-towel germination test
The germination rate is the percentage of seeds in a sample that sprout under good conditions. You can measure it at home in two or three weeks with a paper towel, and it answers the question the viability tables cannot: how good is this packet.
Nebraska's G2090 describes the test this way, in summary. Count out a set number of seeds, such as 25 or 50. Place them between moist paper towels, cloth or blotting paper in a covered dish so they do not dry out. Label each lot. Keep them at 70 to 75 °F. Count seeds as they sprout and make the final count at 2 to 3 weeks. Wisconsin's Dane County page describes a smaller version: 10 seeds rolled in a damp half paper towel inside a partly sealed plastic bag, kept warm, checked every 2 to 3 days so it stays moist, and counted when the packet's days-to-germination period has passed.
The arithmetic is the same for any sample size:
- Germination percent = seeds that sprouted / seeds tested x 100.
- Seeds to sow = plants you want / (germination percent / 100).
Worked through: 28 of 40 seeds sprout. 28 / 40 = 0.70, so the germination rate is 70 percent. If you want 10 plants, sow 10 / 0.70 = 14.3, rounded up to 15 seeds. Round up, never down, because the fraction is an estimate.
Physical principle Sample size sets how much the result can tell you. With 10 seeds, each seed is 10 percentage points, so one seed more or less moves the result from 60 to 70 percent. With 50 seeds, one seed is 2 points. Ten seeds tells you whether a packet is dead or alive; 25 or more gives a number you can sow by. Use the larger count when the packet holds enough seed to spare.
Interpreting the result is where the two sources differ again, mildly. Wisconsin's page says that below 40 percent you should buy fresh seed, because seeds that do sprout from such a lot may be stunted and less productive, and that a moderate result such as 5 of 10 can still be planted if you sow more seed than usual. Nebraska's G2090 says lots with lowered germination may still be usable if sown at higher rates, and notes that weakly sprouting seeds die more often once in soil. Convention Read that together: above about 40 percent, sow extra by the arithmetic above; below it, replace the seed. A sprout that takes twice as long as its neighbors to appear counts toward the percent but is a weaker plant.
The test conditions are warm and moist on purpose. A packet that germinates at 70 percent on a towel at 72 °F will do worse in a cold, wet bed in April. That gap is not a flaw in the test; it is why soil temperature, taught in Module 6, still governs when you sow outdoors.
Record each test in the sowing sheet of the season log: the packed-for year, the seeds tested and the germination percent. Next spring, that column tells you which packets to test again and which to replace.
Direct sowing or transplanting
Direct sowing means sowing seed where the plant will grow to maturity. A transplant is a young plant started in a container, indoors or in a greenhouse, and moved into the garden. Neither method is better in general. Each crop has a usual method, and the reasons are physical: how long the crop needs, how warm it needs to be, and how its roots respond to being moved.
Why some crops are transplanted
Tomato, pepper and eggplant need a long, warm season. Started from seed outdoors after the soil warms, they often do not have time to produce before fall. Minnesota's planting guide puts it directly: in its climate, those warm-season crops will not mature if seeded directly in the garden. Starting them indoors 5 to 9 weeks earlier moves that part of their growth into the weeks when the garden is still too cold. Montana State's guide makes the same point for short seasons: buying transplants or starting seed indoors shaves time off the outdoor season a crop needs.
Cabbage and broccoli are cool-season crops usually transplanted for a related reason: a transplant set out early gets the crop to harvest before summer heat. Lettuce, kale and onion are often grown either way.
Why some crops are sown directly
Beans, peas, sweet corn and spinach grow fast from large seeds, so a transplant buys little time. Convention Root crops are usually sown directly for a stronger reason. Minnesota's beginner planting guide says radishes, carrots and beets do not tolerate transplanting and need to be direct seeded; Minnesota's farm guidance qualifies that for beets, which growers transplant from paper pots (Module 6). The edible part of those crops is the root itself; a root bent or broken at transplanting grows forked or stunted. A source can be quoted accurately and still be too absolute, though. Minnesota's own guidance for vegetable farms says more and more growers transplant beets from paper pots, and calls transplanting carrots an uncommon practice. Direct sowing is the simplest starting method for beets; young beet seedlings can also be transplanted carefully. For carrots and radishes, sow directly. Convention
Cucumber and squash sit in between. They are usually sown directly, and Colorado State gives a short transplant age of 2 to 3 weeks for growers who want a head start. Minnesota's seed-starting page notes that cucumbers and squash transplant poorly and recommends fiber or paper pots that go into the ground with the plant, so the roots are not disturbed.
| Crop | Usual start | Transplant age, weeks | Source for age |
|---|---|---|---|
| Tomato | Transplant | 5 to 7 | Colorado State |
| Pepper | Transplant | 6 to 8 | Colorado State |
| Eggplant | Transplant | 6 to 9 | Colorado State |
| Cabbage, broccoli | Transplant | 5 to 7 | Colorado State |
| Lettuce, kale | Either | 6 to 8 | Cornell (Rockland County) |
| Onion | Either (seed, sets or plants) | 10 to 12 | Cornell (Rockland County) |
| Basil | Either | 6 to 8 | Minnesota |
| Cucumber, summer squash, winter squash | Direct; transplant in pots that go into the ground | 2 to 3 | Colorado State |
| Bush bean, pea, spinach, sweet corn | Direct | not transplanted | - |
| Radish, carrot | Direct | not transplanted | Minnesota |
| Beet | Direct is simplest; young seedlings can be transplanted carefully | no age published in our sources | - |
| Potato, garlic | Planted from tubers or cloves | not grown from seed | - |
Transplant ages vary between sources too. Minnesota's seed-starting table gives tomatoes 5 to 6 weeks indoors and peppers and eggplant 9; Colorado State gives 5 to 7 and 6 to 8. The planting calendar uses Colorado State's figures and names the others where they appear. Convention An older, larger transplant is not better: Montana State's guide prefers a smaller, younger plant over one already flowering or fruiting.
Starting seeds indoors
Indoor seed starting gives you a choice of varieties no garden center stocks, and it costs attention. A tray of seedlings needs checking every day for six to ten weeks: water, light height, temperature, and later potting up and hardening off. If your weekly hours are short, buying transplants for the transplanted crops is a sound first-season choice, and you can start seeds in a later year.
Containers and mix Go deeper
Seedlings need a container with drainage holes and a soilless mix: a sterile seed-starting medium, usually peat or a similar fiber with vermiculite or perlite, containing no actual soil. Minnesota's seed-starting page recommends a commercial seed-starting mix for that reason. Garden soil carries the fungi that cause damping-off, the sudden collapse of a young seedling at the soil line. Utah State's fact sheet names damping-off as the usual cause when seedlings fall over and die, and ties it to cool, wet conditions, reused unclean containers and crowding. Minnesota says reused containers should be disinfected first, following the label of the disinfectant you use.
Minnesota and Montana State both suggest sowing two or three seeds per cell and thinning to one seedling once they come up. Preference We snip the extras at the soil line with scissors rather than pulling them, so the keeper's roots stay undisturbed.
Light: hours and distance
Light is the factor indoor growers most often get wrong. Physical principle A seedling short of light stretches toward it, producing a tall, thin, pale stem that cannot hold itself up. Utah State's fact sheet says natural light through a window is insufficient in most situations, and Minnesota's page advises against windowsills because they run too cold at night and too hot by day.
The two sources give close but different figures:
| Condition | University of Minnesota Extension | Utah State University Extension |
|---|---|---|
| Hours of light a day | 12 to 16, on a timer; not continuous | 12 to 14 or more, on a timer |
| Light height above seedlings | No more than 4 in; about 2 in is ideal | 2 to 3 in; raise lights as plants grow |
| Temperature | Air above 60 °F; mix can run up to 5 °F cooler than the air | Nights 60 to 65 °F, days about 10 °F warmer; cool-season crops about 55 °F nights, 65 °F days |
| When and how to feed | After several sets of true leaves: water-soluble fertilizer at one-quarter strength once a week | If the label gives no seedling rate: half the normal concentration once a week |
| Hardening off | About 2 weeks | At least 2 weeks before transplanting |
The common ground is what to act on. Convention Give 12 to 16 hours of light from a timer, keep the lights a few inches above the leaves, and raise them as the plants grow. Utah State notes that ordinary fluorescent shop lights work and that lights sold as grow lights are not required; it also warns about leaf scorch from lights that give off a lot of heat. That warning is the reason the distance comes from your light's own instructions when they differ from these figures: an LED panel and a fluorescent tube put out very different heat and intensity at 2 inches. Product-specific Follow the manufacturer's recommended hanging height for the fixture you own.
True leaves are the leaves that appear after the first pair of seed leaves and have the shape of the crop's mature leaves. They are the signal for feeding and for potting up.
Temperature and bottom heat
Germination is faster in warm mix, and Minnesota's page notes that bottom heat helps germination and root growth. Once seedlings are up, warmth becomes a problem: Utah State says plants grown warmer than its ranges turn spindly, and advises removing or unplugging heat pads if temperatures are too warm. A heat mat is for germination; it is not needed for growing on.
Water and feeding
Seedlings in a small cell can dry out and die in a day, and they can also drown. Utah State suggests lifting the tray: when it feels much lighter than it did after a full watering, water it. Watering from below, by setting cells in an inch or two of water, works well; Utah State adds an occasional top watering to flush out fertilizer salts and says to discard drainage water rather than let it soak back in.
Soilless mixes carry few nutrients, so seedlings kept more than a few weeks need feeding. The figure the course uses is the more conservative of the two published ones. Convention Use the seedling rate on your fertilizer's label if it gives one. If it does not, feed at half strength or less once a week after the first true leaves, as Utah State and Minnesota describe. Utah State's advice is to err lean: too much fertilizer makes soft, weak growth that pests prefer.
Potting up
Potting up means moving a seedling into a larger container before its roots fill the first one. Utah State says to pot up when leaves of neighboring plants overlap or roots form a dense mat at the bottom; Montana State says when 2 or 3 true leaves show. Plant the seedling at the same depth in moist mix and handle it by a leaf, not the stem, because a crushed stem does not recover and a torn leaf does.
Grow lights, heat mats and the timers and power strips that run them are electrical equipment used near water. Use each one only as its manufacturer directs, plug it into a properly rated outlet, and keep cords and connections away from trays and spills. Minnesota's seed-starting page advises against plugging a heat mat into a light timer. Ask a licensed electrician before adding a circuit, running power outdoors or to a cold frame, or using an extension cord as permanent wiring. This course gives no wiring advice.
Buying, hardening off and planting out
Choosing transplants to buy
Montana State's guide gives a short checklist for buying transplants. Convention Choose a stocky plant over a tall, spindly one. Turn the leaves over and look for insects. Check that the plant is not root-bound, with roots circling the pot. Pass over plants already flowering or carrying fruit; a smaller, younger plant establishes better. To check roots, tip the pot and slide the root ball out partway; white roots that hold the mix together without a thick mat are what you want.
Ask the seller whether the plants have been hardened off. Plants moved straight from a greenhouse bench need the same hardening as plants from your basement.
Hardening off
Hardening off is the gradual exposure of indoor-grown seedlings to outdoor sun, wind and temperature before planting. Physical principle A seedling grown indoors has soft, thin-skinned leaves adapted to still air and dim light. Moved straight into full sun and wind, it loses water faster than its roots can supply and its leaves scorch. Over a week or two outdoors, its growth firms up. Maryland Extension describes it as a change from soft, succulent growth to firmer growth; Utah State says some leaves may yellow or brown along the way and that this is normal, because the plant is growing new leaves suited to outdoor light.
The sources agree on the shape and differ a little on the length:
- South Dakota State University Extension: 7 to 14 days. Start with about 3 to 4 hours in a protected, shaded spot during the warmest part of the day, add a few hours each day, and for the last one or two days leave plants out overnight if night temperatures look favorable. Keep them in if daytime temperatures are forecast below 45 °F or wind or rain threaten. Water less often, but do not let them wilt.
- University of Maryland Extension: 1 to 2 weeks. Start in a shaded, protected spot on warm days, bring plants in at night, and increase sun each day. Do not put tender seedlings out on windy days or below 45 °F. Cucumbers and melons may stay out overnight if it will not fall below 50 °F.
- Utah State: begin at least two weeks before transplanting; keep warm-season crops such as tomatoes, peppers, squash and melons away from temperatures below about 45 to 50 °F.
Here is one 10-day schedule built from that common pattern. It is our worked plan, not a schedule any one source prints; stretch it to 14 days if the weather turns.
| Day | Outdoors | Where |
|---|---|---|
| 1 to 2 | 3 to 4 hours, warmest part of the day | Full shade, out of wind |
| 3 to 4 | 5 to 6 hours | Shade, with an hour or two of morning sun |
| 5 to 6 | 7 to 8 hours | Half-day sun |
| 7 to 8 | All day; in at night | Full sun |
| 9 to 10 | Day and night, if the night forecast is above 45 °F (50 °F for cucumbers and melons) | Where they will be planted |
On any day with a forecast below 45 °F, strong wind or a hard rain, skip a step rather than push. A missed day costs a day; a scorched or chilled seedling costs weeks.
Planting out
Plant out on the date the calendar gives for the crop, adjusted for this year's weather and soil temperature as Module 6 teaches. Utah State's fact sheet describes the technique:
- Water first. Water the plants well in their pots before planting, so the root ball holds together. Minnesota's planting guide says the same.
- Dig the hole. Make it about twice as wide as the root ball and as deep as the root ball, so the plant sits at the depth it grew in the pot.
- Remove the plant. Push the root ball out from the bottom rather than pulling the stem. If roots circle the ball in a thick mat, loosen them with your fingers or a few shallow vertical cuts.
- Set it and firm it. Set the plant, fill around it, and firm the soil gently by hand. Tomatoes are the exception on depth: Utah State notes that they root along the buried stem and may be planted deeper.
- Water it in. Water immediately to settle soil around the roots. Keep the root ball moist, which may mean daily watering until the plant is established; South Dakota State says to water every morning until roots grow into the garden soil.
Plants in peat pots go in pot and all. Utah State says to slit the pot and cover it fully with soil; Minnesota says to keep the rim below the surface, because an exposed rim wicks water away from the roots.
On time of day, the sources differ. Utah State says to transplant in the morning or on a cloudy day; Montana State says the cool of the morning; Minnesota says late afternoon or a cool, cloudy, calm day. Preference What they share is avoiding planting into midday sun and wind. Pick whichever cool part of the day you have.
Direct sowing and thinning
For direct-sown crops, read the packet's depth and in-row spacing, check the soil temperature against the crop's minimum in the crop guide, and sow. Minnesota's planting guide suggests a dibble or a pencil marked at the depth to keep holes consistent. Montana State suggests a string line, so you can tell your rows of seedlings from weeds that come up at the same time.
Thinning is removing extra seedlings so the ones that remain stand at the packet's final spacing. It feels wasteful, and it is the step most beginners skip. Physical principle Crowded plants compete for the same water, light and nutrients, and crowded root crops cannot swell; a carrot row left unthinned produces a row of thin carrots. Thin when seedlings have their first true leaves, and again later if the packet gives two spacings. Snip rather than pull where roots are tangled.
Write each sowing and planting date in the season log, with the variety and the date the first seedlings emerged. The emergence date checks the soil-temperature decision; a crop that took three weeks to come up was sown into soil that was too cold.
2. See it See it
Two of the course's fictional cases. Frost dates, test results and every other figure in them are invented for the examples; they are not lookups for any real place.
The Okafor garden: a germination test and a split decision. Ada and Chidi Okafor are growing tomato, pepper, bush bean, lettuce, cucumber and basil in two 4 x 8 ft raised beds. Their fictional last spring frost is April 20. This is their first garden, and they have about 3 hours a week.
They found a two-year-old lettuce packet in a kitchen drawer. Lettuce is listed at 5 years by both Nebraska and Wisconsin, so the age alone does not condemn it, but a kitchen drawer is not cool, dry storage. They ran Nebraska's test in early February with 40 seeds on a damp towel in a covered dish on top of the refrigerator. At 14 days, 28 had sprouted: 28 / 40 = 70 percent. That is well above Wisconsin's 40 percent replace line, so they kept the packet and sow extra: for every 10 lettuce plants they want, 10 / 0.70 = 14.3, rounded up to 15 seeds.
The calendar's indoor windows for their crops, from Colorado State's transplant ages: tomatoes go out from May 4 (2 weeks after the last frost), so seed goes in 5 to 7 weeks earlier, March 16 to March 30. Peppers, at 6 to 8 weeks, would be sown March 9 to March 23. Basil, at 6 to 8 weeks before planting out around April 20, would be sown February 23 to March 9.
With 3 hours a week, they started only tomatoes and basil, in one tray under a shop light on a timer, and chose to buy pepper transplants. Bush beans and cucumbers they will sow directly. Their hardening-off plan for the tomatoes runs April 24 to May 3, ten days, to plant out on May 4.
- Known: the lettuce packet's germination rate under test conditions (70 percent from 40 seeds); the indoor windows the calendar computes from their fictional frost date; what they chose to start and what to buy.
- Assumed: that the shop light's maker's recommended height suits seedlings at 2 to 3 inches (their assumption, checked against the fixture's instructions before they hang it); that the April 20 date holds this year (Module 6's caution applies).
- Open: whether 70 percent on a towel becomes 70 percent in a cool April bed. Settled by their own season log: the sowing sheet records seeds sown and seedlings counted.
- Open: whether the bought peppers were hardened off. Settled by the garden center that sells them; they ask at purchase.
The Lindqvist garden: transplanting a crop that dislikes it. Nils and Karin Lindqvist have a short fictional season: last spring frost May 25, first fall frost September 15. In Module 6 they found that a 100-day winter squash does not fit from direct seed. They chose a variety whose packet prints 85 days to maturity, confirmed in the seed company's catalog that the count starts at sowing, and decided to start transplants 3 weeks ahead. Module 6's result is that it potentially fits under their assumptions, with about a week to spare.
Squash transplants poorly, by Minnesota's account, so they sow in paper pots that go into the ground whole, two seeds per pot, thinned to one. The outdoor date for a very tender crop is 2 weeks after the last frost, June 8. Three weeks earlier is May 18, their sowing date. They harden the seedlings off from June 1 to June 7 and keep them in any night forecast below 50 °F. Maryland gives that figure for cucumbers and melons; applying it to squash, a close relative, is their assumption.
- Known: the packet's 85 days; the fictional frost dates; the outdoor date of June 8 from Colorado State's very-tender window.
- Assumed: that starting transplants 3 weeks early removes about 21 days from the outdoor time (Module 6's labelled assumption); that Maryland's 50 °F night limit for cucumbers and melons is a fair guide for squash.
- Open: whether the 85-day figure holds in their cool season, since days to maturity is an average. Settled by their harvest log at season's end, which records the first harvest date.
Free demonstrations and references:
- Starting seeds indoors (University of Minnesota Extension): containers, mix, light hours and height, feeding, and a weeks-indoors table by crop.
- Starting Vegetable Seeds Indoors: IV. Seedling Culture and Transplanting (Utah State University Extension): temperature, light, watering, potting up, hardening off and a troubleshooting section with photos of leggy seedlings and damping-off.
- Vegetable Garden Seed Storage and Germination Requirements (Nebraska Extension G2090): the seed longevity table and the germination test.
- Harden Your Transplants Prior To Planting Your Garden (South Dakota State University Extension): the day-by-day hardening pattern and weather limits.
3. Practice Practice
Minimum: Inventory your packets, choose a start method for each crop and write each transplant's hardening-off start date; skip the germination test. Time: about 45 minutes of work spread over two to three weeks, plus 5 minutes every 2 or 3 days to check the test. Materials: your seed packets, paper towels, a plate or covered dish or sealable plastic bag for each packet tested, a marker, a warm spot near 70 °F, and the season log.
- Inventory your seed. For each packet you hold, write the crop, variety, packed-for year, days to maturity and whether that figure counts from seed or transplant. Use Montana State's packet list as the checklist.
- Go deeper Pick what to test. Test any packet older than the viability years in the table above, any packet stored somewhere warm or damp, and any packet you plan to sow heavily.
- Go deeper Run the test. Count out 25 seeds if the packet can spare them, or 10 if not. Lay them on a damp paper towel, fold or roll it, and keep it covered at about 70 to 75 °F. Label it with the variety and date.
- Go deeper Count and compute. Check every 2 or 3 days and keep the towel damp. At the end of the packet's germination period, or at 2 to 3 weeks, count the sprouted seeds. Compute the percent and the seeds to sow for the number of plants you want.
- Decide start method per crop. For each crop, write direct sow, start indoors or buy transplants, with one reason. Use the table above, the calendar's indoor dates and your weekly hours.
- Write a hardening-off schedule. For each transplanted crop, count back 7 to 14 days from its planting-out date and write the start date of hardening off.
- Go deeper Record it. Enter each packet's test, packed-for year and germination percent in the sowing sheet of the season log, and tick "seeds tested" on the start-of-season checklist.
4. Your garden Your garden
5. Check your work Check your work
Criteria
- Does every packet in your inventory show whether its days to maturity counts from seed or from transplant?
- Did each germination test use at least 10 seeds, and did you compute both the percent and the seeds to sow?
- Does every root crop on your list (radish, carrot, beet) say direct sow?
- For each crop you start indoors, can you name the indoor sowing window from the calendar and the light hours and height you will use?
- Does each transplanted crop have a hardening-off start date 7 to 14 days before its planting-out date?
- Is each result written in the season log rather than on the packet?
Worked example
Against the criteria, the Okafors' fictional plan holds up. The lettuce test used 40 seeds and produced both numbers: 70 percent and 15 seeds per 10 plants. Their root-crop question does not arise; their crops include none. The tomatoes and basil have indoor windows from the calendar and a light schedule, and the tomatoes have a ten-day hardening plan ending the day before May 4. One gap: their basil has no written hardening-off date yet. Basil is tender and goes out around April 20, so hardening starts about April 10. They add it.
Common mistakes
- Reading a transplant figure as a seed figure. A 65-day tomato sown on May 1 is not ripe on July 5. Check which count the packet uses.
- Starting too early. Seedlings kept indoors weeks past their transplant age grow leggy and root-bound. Penn State's Pike County Master Gardeners warn that plants left indoors too long turn weak. The calendar's window has a start date for a reason.
- Lights too high. A light hung a foot above seedlings produces stretched, falling stems. The fix is lowering the light, not more fertilizer.
- Skipping hardening off. Bleached, papery leaves a day or two after planting out are the usual sign of sunscald on unhardened plants.
- Not thinning. A row of carrots at seed spacing is a row of thin carrots.
- Testing seed in the cold. A towel test in a cool room underestimates germination. Keep it near 70 to 75 °F.
What is still unresolved
A towel test tells you how a packet sprouts in ideal conditions. It does not tell you how it will do in your soil this spring; the emergence counts in your season log do. Viability years and transplant ages are published averages and differ between extension services; your own records settle them for your seed and your setup. Whether a light, a heat mat or an outlet is suitable is settled by the manufacturer's instructions and, for any new or outdoor circuit, an electrician. Planting-out dates still depend on this year's weather and soil temperature, which Module 6 covers.