Let's head to the nursery!
Buying seeds or transplants is the easy part. Knowing how deep to plant and how to avoid the mistakes that quietly kill new plants is what actually determines whether they take. Here's the real science behind getting things in the ground right.
Both are right. The question is just which one fits what you're growing
At the garden center you'll see two things to plant: seed packets, and young plants already growing in pots. A packet of 50 tomato seeds costs about the same as one transplant, but seeds take 6 to 8 weeks to reach transplant size. For fast crops, that math favors seed. For slow ones, buying a transplant saves real time.
Start from seed when the crop has a deep taproot that hates being moved, like carrots, beets, or radishes. It's also the better choice for fast-growing crops such as lettuce or spinach, which reach harvest in 4 to 6 weeks either way, and for anything you're planting in quantity, since a whole row of basil is dramatically cheaper from a packet than as individual transplants.
Buy a transplant when the crop is a slow starter, like tomatoes, peppers, or eggplant, which need 8 to 10 weeks from seed before they're transplant-size. It's also the right call when your season is short and you need the head start, or when it's an herb you want producing leaves now instead of in a month.
I do both. Tomatoes and peppers, I always buy as transplants. Carrots and beans, I always seed directly. Lettuce, I plant from seed because I sow it every two weeks for a continuous harvest. Once you know your garden, you'll fall into a natural rhythm.
One date organizes almost everything else about your planting year
Picture this: you're at the nursery in early spring, the tables full of beautiful tomato transplants, and the staff member asks what your last frost date is. If you don't know it, that matters more than you'd think, since everything in your planting calendar works backward or forward from that single date.
Your last frost date is the average date of the last spring freeze in your area. You can find it by searching "[your city] last frost date" online. Warm-season crops, like tomatoes, peppers, and squash, can't go outside until after it. Cold-season crops, like lettuce, kale, and peas, can go out well before it.
Your USDA hardiness zone is a rating based on your area's average annual minimum winter temperature. It tells you whether a perennial plant will survive your winters, so check it against any plant tag before buying something that's supposed to come back year after year.
Days to maturity tells you how many days a crop needs, from transplant, or from germination for direct-seeded crops, until first harvest. It's printed on every seed packet and plant tag. Compare it to how many growing days are left in your season before deciding whether a variety will actually finish in time.
Succession planting means planting the same crop in small batches every 2 to 3 weeks instead of all at once. It produces a steady harvest instead of a glut followed by nothing, and lettuce and beans are the easiest crops to try it with first.
Compare the days-to-maturity number on the tag to how many growing days you have left this season, counting from today to your first fall frost date. If it's close or over, choose a faster-maturing variety instead. For example a tomato that needs 90 days in a 100-day season will barely make it, but an early bird tomato might.
The same test professional growers use to know if the conditions are actually right
Good soil prep doesn't end when you stop amending it. Right before you plant, the soil needs to be in the right physical state, not too wet and not too dry, or you can undo weeks of good preparation in a single afternoon. Working or planting in soil that's the wrong moisture compacts it, crushing the pore spaces that roots and water both depend on.
Grab a small handful of soil from your planting area and squeeze it in your fist, then open your hand and look. If it stays molded in a wet, sticky ball, the soil is too wet to work. If it falls apart like dust and won't hold together at all, it's too dry. What you want is soil that crumbles into loose, small clumps when you open your hand — that's the sign your soil has good structure, or tilth, with enough open space for water, air, and roots to move through it.
Soil that's too wet compacts under a shovel or a footstep, crushing the pore spaces roots and water depend on and inviting a hard crust once it dries. Soil that's too dry can't supply the moisture a germinating seed needs. The crumble test is a two-second way to check that the conditions are actually right before you start.
Soil moisture needs to stay even, roughly around 50 percent of the soil's available water capacity, neither soaked nor dry. Uneven moisture in the seed zone is a leading cause of patchy, uneven emergence, and can cut yields by as much as 8 to 10 percent in some cases.
Soil temperature matters more than air temperature for germination, and it can vary noticeably across a single planting bed depending on soil color and how much residue or mulch is covering it. Corn, for example, needs a soil temperature of about 55 to 60 degrees Fahrenheit to germinate reliably — cold soil delays or prevents germination even when everything else is right.
Roots need oxygen to respire, the same as any other living tissue, and planting too deeply can cut off that air exchange between the soil and the surface. This is a particular risk in heavy, clay-based soils, where compacted, waterlogged pore spaces leave roots with almost nothing to breathe.
The small details that separate strong germination from seeds that just sit there
The general rule for direct-sown seeds is to plant them at a depth of about two to three times their width. A tiny lettuce seed goes just below the surface; a big bean seed goes about an inch deep. This isn't a guess passed down through tradition either, it comes out of decades of agricultural research into exactly how deep different seeds need to be to balance two competing risks: drying out near the surface, and running out of stored energy before they reach it.
Tiny seeds like lettuce, spinach, and petunias should be pressed gently into the surface rather than buried, since many of them actually need light to germinate at all.
Small seeds like carrots and parsnips are typically planted about a half inch deep, which balances their limited energy reserves against the risk of drying out too close to the surface.
Medium seeds like peas need about an inch of soil over them to stay protected while they still have enough energy to reach the surface.
Large seeds like beans and corn carry enough stored energy to push up from 1 to 1.5 inches deep, which also gives them better protection from surface drying and hungry birds.
The rules of thumb above get you close, but exact numbers vary by crop. This is the reference to come back to once you know what you're planting.
| Vegetable | Seeding Depth | In-Row Spacing | Row Spacing |
|---|---|---|---|
| Asparagus (roots) | 6 inches | 18–24 inches | 36 inches |
| Beans, Bush | 1–1.5 inches | 2–4 inches | 36 inches |
| Beans, Pole | 1–1.5 inches | 4–12 inches | 36 inches |
| Beets | 0.5 inches | 2 inches | 18–36 inches |
| Carrots | 0.25–0.5 inches | 2–3 inches | 18–36 inches |
| Collards | 0.5 inches | 8–16 inches | 36 inches |
| Corn, Yellow | 1 inch | 12–18 inches | 36 inches |
| Cucumbers | 0.5 inches | 2–3 feet | 3–5 feet |
| Lettuce, Head | 0.25 inches | 12 inches | 12–18 inches |
| Okra | 1 inch | 1.5 feet | 2–3 feet |
| Peas, Green | 2 inches | 2 inches | 3 feet |
| Radish | 0.5 inches | 2 inches | 1 foot |
Plant a seed too shallow and it dries out fast, especially on warm, sunny, windy days, and it's also more exposed to birds and insects looking for an easy meal. Plant it too deep and it faces the opposite problem: deeper soil is cooler, which can delay or prevent germination outright, and the seed has to spend a finite store of energy pushing up through more soil than it has fuel for. A hard crust on top makes this worse, sometimes causing a seedling to exhaust itself and die underground before ever reaching the surface — and research on ginseng has shown that deeper planting can also increase the risk of damping-off, a fungal disease that thrives in the cool, damp conditions found deeper in the soil.
A long-term study at the Oklahoma Panhandle Research and Extension Center found that corn planted at a 2.5-inch depth consistently outyielded corn planted at 1.5 inches, year after year. The explanation lies in the roots: corn seedlings grow shallow primary roots for their first two to three weeks, then switch over to deeper nodal roots that support the plant for the rest of its life. Planted too shallow, the crown where those nodal roots emerge sits exposed near the hot soil surface, leading to root damage and drying. The plants survive, but they're stunted and never fully catch up — proof that a single decision made at planting time can shape a plant's entire life.
For years, firming the soil around a seed was explained as a way to press it against liquid water in the soil. Research from the USDA's Agricultural Research Service found something more interesting: 85 percent or more of the water a seed absorbs actually comes from water vapor, not liquid water. Even dry-feeling soil holds relative humidity above 99 percent in its pore spaces. Firming the soil isn't about squeezing out liquid moisture. It's about closing air gaps so the seed sits inside a small, stable, high-humidity pocket instead of a drier air gap that would slow or prevent germination. A gentle press or pat is all it takes; there's no need to stomp on it, and doing so risks compacting the soil instead.
Plant 2 to 3 seeds per spot, a practice called overseeding, since some percentage of seeds simply won't germinate no matter how carefully you plant them. Once seedlings emerge and grow their first set of true leaves, not the small first leaves that unfurl at germination, but the second set that actually look like the plant's mature leaves, thin to the strongest one by snipping the extras at soil level with scissors. Don't pull them. Pulling disturbs the roots of the seedling you're keeping, while a clean snip removes the competition without the collateral damage.
A transplant needs its roots into good soil with as little disturbance as possible, and then help settling in with water and a little shade for the first few days. Getting the hole right matters as much as anything you do with the plant itself.
Dig the hole 1.5 to 2 times wider than the root ball; for trees and shrubs, aim for 2 to 3 times as wide. A wider hole gives new roots an easier path to spread laterally into the surrounding native soil instead of staying cramped inside the planting hole. The hole's depth should match the depth of the root ball exactly, or 1 to 3 inches shallower in heavy clay soil, since clay tends to let a root ball settle further down over time and end up buried too deep. Avoid loosening the soil at the very bottom of the hole, since that loose soil can compress under the plant's weight and let it sink lower than intended. It also helps to roughen the sides of the hole with a shovel, since smooth, glazed walls, a common side effect of digging with a spade in heavier soil, can actually block new roots from pushing outward into the surrounding ground.
The single most common, and most fatal, transplanting mistake is planting too deep. The root collar, sometimes called the root flare, is the point where a plant's stem or trunk widens into its root system, and it needs to sit at or just slightly above the surrounding soil grade. Many nursery-grown plants arrive with their root collar already buried under excess soil or potting mix, so it's worth brushing away the top inch or two of soil in the pot to find the real root collar before you ever put the plant in the ground. Bury it too deep and the bark, which is meant to be exposed to air, stays in constant contact with wet soil and begins to rot. Loose soil piled over the root ball can also encourage new roots to circle the trunk instead of growing outward — these are called girdling roots, and over years they slowly strangle the plant by cutting off its own flow of water and nutrients. One exception worth remembering: tomatoes are the rare plant that actually benefits from being buried deeper than they sat in their pot, since they grow new roots all along a buried stem.
Before a containerized plant goes into its hole, remove the container completely, even if it's labeled biodegradable. A peat or fiber pot left in place can act like a wick, pulling moisture away from the roots and stressing the plant right when it needs stability most. If the roots are circling tightly around the inside of the pot, the plant is root-bound, and those roots need to be loosened or cut so they don't keep growing in the same circular pattern and eventually girdle the plant. Bare-root plants need their roots spread out naturally in the hole in their normal growing position, not stuffed into a hole that's too small, which forces them into unnatural bends that can permanently damage the root system.
It's tempting to fill the hole around a new plant with the richest soil and compost you have, but too much amendment in just the planting hole creates what's called a moisture gradient: the surrounding native soil is drier or denser than the cushy mix in the hole, so roots have little incentive to ever grow past the edge of that hole. The fix is to backfill mostly with native soil, mixed with at most a little compost, so the roots are encouraged to keep exploring outward into the soil they'll actually be living in for years. Add the soil back in a few inches at a time, watering each layer to help it settle and eliminate air pockets, and firm it lightly with your foot rather than stomping it down, which can damage roots and compact the soil you just worked to keep loose.
I used to fill every planting hole with the richest compost I had, thinking I was giving the plant the best possible start. It took a few seasons of oddly stunted shrubs to learn what was actually happening: I'd built a comfortable little bathtub, and the roots had no reason to ever leave it. Now I mix in just a little compost with the native soil I dug out, and the plants that used to sulk in place are spreading out and thriving instead.
Build a small berm, just 1 to 3 inches high, in a ring just outside the planting hole to catch and hold water instead of letting it run off. Add a 2 to 3 inch layer of organic mulch, like bark, to hold in moisture and keep weeds down. Never pile that mulch directly against the trunk or stem — a mound of mulch against the base, sometimes called a mulch volcano, does the same damage as planting too deep: it holds constant moisture against the bark, inviting rot, insects, and disease. Keep mulch a few inches back from the stem so air can still circulate.
Corn, beans, and squash planted together make up the Three Sisters, a companion planting system used by Indigenous peoples across North America for centuries, and it still works today. The corn acts as a natural pole for the beans to climb, the beans fix nitrogen in the soil for the corn and squash, and the squash's broad leaves shade the ground and help deter pests. It works best in a larger bed with enough room for all three.
Everything above comes back to these three failure points. If a plant is struggling and you're not sure why, check here first.
Piling mulch directly against a plant's trunk or stem creates constant moisture against the bark, which invites rot, insects, and disease. Keep mulch a few inches back from the base instead.
Planting the root collar below soil level lets the trunk or stem rot in wet soil and lets girdling roots form, both of which slowly kill the plant. Find the true root collar, brushing away extra soil if needed, and keep it at the surface.
Working soil that's too wet, or heavy foot traffic over root zones, crushes the pore spaces roots need for oxygen. Run the crumble test before working any bed, and use stepping stones or a fixed path instead of walking across planting soil.
The transition most people skip, and the one that costs the most when they do
If you started seedlings indoors, or bought transplants that were raised in a sheltered greenhouse, they've spent their whole life somewhere with no wind, filtered light, and a stable temperature. Moving them straight outside is a shock the plant has to recover from before it can grow again, and that recovery period is exactly what hardening off is designed to prevent.
Transplant shock shows up as wilting, yellowing leaves, and stunted growth, and it comes from two things happening at once: root damage during the move, and a sudden, drastic change in growing conditions. A plant's ability to absorb water and nutrients is temporarily disrupted by that root damage, right as it also has to adapt to new light, temperature, and soil conditions it's never experienced before.
A sheltered spot, out of full sun, for 1 to 2 hours in the morning, then back inside or into shade for the rest of the day.
Morning sun for 3 to 4 hours. The plants should start looking sturdier and less fragile by this point.
All day, including direct sun, and overnight if there's no frost risk. If they handle a full day without wilting, they're ready to go in the ground.
Over this week to two weeks, the plant is doing real physiological work: building a thicker leaf cuticle, developing sturdier cell walls, and learning to use water more efficiently. That's what lets it withstand the wind, sun, and temperature swings of the real world instead of wilting the first time it faces them.
I once transplanted six tomato seedlings I'd babied indoors for eight weeks straight outside on a hot, sunny day, without hardening them off first. By evening, three of them looked nearly dead. They recovered, but it took two weeks of slow growth before they took off again. Now I always harden off my transplants — skipping that step cost me almost a month of production for the sake of saving a single week.
The calendar is a guideline. The soil thermometer is the real answer.
Your last frost date tells you the earliest it's generally safe to plant, but the soil itself is what actually determines whether a seed will germinate or a transplant will thrive. Two years with the same last frost date can still have very different soil temperatures in early spring, so it's worth checking the soil directly instead of just trusting the calendar.
Peas, lettuce, spinach, and radishes germinate well in cool soil and can handle a light frost once they're up. Plant them 2 to 4 weeks before your last spring frost date.
Tomatoes, peppers, beans, corn, and squash need warm soil to germinate or establish well, and they're killed outright by frost. Wait until the soil is consistently warm before planting, even if the calendar says it should be safe.
Use a soil thermometer pushed about 4 inches deep, check it at the same time every day for three days in a row, and take your reading in the morning, since that's when it's most accurate and least affected by the previous day's sun.
A quick way to work backward from a problem to its likely cause
Even with good technique, something occasionally doesn't take. These three problems cover almost everything that goes wrong after planting, and each one has a short list of usual suspects worth checking before you give up on the plant.
Check the soil temperature first, since it may simply be too cold for that crop. Then check your planting depth, since seeds planted too shallow or too deep both fail for different reasons. Check whether the soil has stayed consistently moist, and consider the age of your seed, since older seed loses its germination rate over time.
Ask whether hardening off was actually completed, since skipping it is the single most common cause. Check that the root collar sits at the correct level, and think back to whether the roots were damaged during planting. Finally, check whether the soil has stayed consistently moist since transplanting, since inconsistent watering causes the same wilting as shock does.
Check for roots that were circled or root-bound and never got loosened before planting. Consider whether the native soil is very different from the potting mix the plant came in, which can slow new root growth into it. Think about whether it was planted at the wrong time of year for that crop, and check for weeds competing for the same water and nutrients.
Work through it in order and nothing gets left to chance
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Condensed from RootDelight's How to Plant Anything, Plant it Right!, Let's Get Growing, and A Scientific Guide to Planting courses.
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