This planting depth calculator tells you how deep to plant seeds, cloves, tubers, slips and crowns. Choose a crop to get its recommended depth, spacing and starting method from our plant database, or measure an unfamiliar seed and the calculator applies the classic rule of two to three times the seed’s width. It also adjusts for soil type, because seeds in light, sandy soil do better a little deeper and seeds in heavy clay do better a little shallower. Getting depth right is one of the simplest ways to improve germination.
How to use the planting depth calculator
- Choose how to find the depth. Pick a crop from the list, or choose to measure the seed if your crop is not listed or the packet is lost.
- Select the crop or enter the seed width. Measure the widest part of the seed with a ruler marked in sixteenths of an inch.
- Choose your soil type. Loam or a raised bed mix uses the standard depth. Sandy soil goes slightly deeper; heavy clay slightly shallower.
- Read the result. The calculator shows the depth, what you are planting, the spacing and the usual way to start the crop.
The two-to-three-times rule
When you have no specific instructions, plant a seed at a depth of about two to three times its width. This rule works because it matches how much stored energy a seed carries. A large bean seed holds enough food to push a sprout up through an inch or more of soil. A tiny lettuce seed holds only enough for a very short journey.
Planting depth ≈ seed width × 2 to 3
- A bean seed about ¼ to ⅓ inch wide goes about 1 inch deep.
- A squash seed about ¼ inch thick goes about ½ to 1 inch deep.
- A tomato seed about ⅛ inch wide goes about ¼ inch deep.
- A lettuce or carrot seed, smaller still, is barely covered with a dusting of fine soil.
Why depth matters so much
Planting too deep is one of the most common reasons seeds fail. A seedling buried too deeply can exhaust its stored energy before it reaches the light, and it never emerges. Deeply buried seeds also sit in cooler soil, which slows germination, and in heavy soil they may struggle to push through.
Planting too shallow causes different problems. Seeds near the surface dry out quickly, can wash away in heavy rain or watering, and are easy pickings for birds. Large seeds left too shallow may germinate but push their roots out into the air.
When in doubt, go shallower. A seed planted slightly shallow and kept moist will usually still germinate. One planted much too deep often will not.
Planting depth for common crops
| Depth | Crops |
|---|---|
| At the surface | Strawberry crowns, set level with the soil |
| ¼ in or less | Lettuce, carrots, tomatoes, peppers, eggplant, onions from seed, basil, parsley, dill |
| ½ in | Spinach, kale, chard, beets, radishes, broccoli, cabbage, cauliflower, cilantro |
| ¾ in | Okra |
| 1 in | Beans, peas, cucumbers, squash, zucchini |
| 1½ in | Sweet corn |
| 2 in | Garlic cloves, measured to the base |
| About 4 in | Seed potatoes and sweet potato slips |
These match the sowing depths in our plant database, which also lists spacing and days to maturity.
Adjusting for soil and season
- Sandy soil: dries out quickly at the surface, so plant a little deeper, roughly a quarter more, so the seed stays moist.
- Heavy clay: can form a hard crust as it dries, which small seedlings struggle to break through. Plant a little shallower and cover seeds with fine compost or vermiculite instead of clay.
- Hot, dry weather: plant at the deeper end of the range, and water consistently.
- Cool, wet spring soil: plant at the shallower end, where the soil warms faster.
Seeds that need light
Some seeds germinate better with exposure to light, and burying them can reduce germination. Lettuce is the best-known vegetable example. Sow it on the surface, press it gently into the soil so it makes good contact, and cover with only the thinnest dusting of fine soil or vermiculite, or none at all. Keep the surface moist until seedlings appear. Seed packets usually note when a seed needs light to germinate.
Planting depth for transplants
Transplants follow different rules from seeds.
- Most vegetables and herbs: plant at the same depth they grew in their pots, with the top of the root ball level with the garden soil.
- Tomatoes: an exception. Tomato stems grow roots wherever they are buried, so plant them deeper, up to the first set of true leaves, or lay leggy plants on their side in a trench with the top curved upward. More roots means a sturdier, more drought-tolerant plant.
- Cabbage-family transplants: can be set a little deeper, up to the first true leaves, which helps leggy seedlings stand upright.
- Strawberries: the crown, where leaves meet roots, must sit exactly at soil level. Too deep and it rots; too high and it dries out.
- Trees and shrubs: never deeper than they grew in the nursery. The point where the trunk flares out should sit at or just above the soil surface.
Bulbs, cloves and tubers
- Garlic: about 2 inches deep, pointed end up. See our guide to planting garlic in fall.
- Onion sets: just deep enough that the tip shows at the soil surface, about an inch.
- Potatoes: plant seed potatoes about 4 inches deep, then pull soil or mulch up around the stems as they grow. This hilling keeps developing tubers covered so they do not turn green.
- Flower bulbs: a common guide is two to three times as deep as the bulb is tall. Tulips and daffodils usually go about 6 to 8 inches deep.
Techniques for accurate depth
- Furrows: draw a shallow trench with the corner of a hoe or a stick, sow along it, then cover. Mark the stick at the depth you need.
- A board: press the edge of a board into prepared soil to make an even furrow of exactly the right depth.
- A dibber or pencil: for large seeds, make individual holes and mark the depth on the tool with tape.
- A finger: the first joint of an adult finger is roughly an inch, a handy measure for beans and peas.
- Firm the soil: press gently after covering seeds so they make good contact with moist soil.
- Cover small seeds lightly: sift fine compost or vermiculite over tiny seeds rather than raking clods over them.
Sowing depth in seed trays
Seeds started indoors follow the same depth rules, but seed-starting mix is lighter and holds moisture better than garden soil, so it is easy to sow small seeds slightly too deep. Many gardeners sprinkle small seeds on the surface of moistened mix and cover them with a thin layer of vermiculite, which lets light through while holding moisture. Cover trays with a clear dome until seeds sprout, and remove it promptly afterward. Our guide on when to start seeds indoors covers indoor sowing in detail.
When seeds do not come up
If seeds fail to appear after the normal germination time, depth is one of the first things to check. Carefully brush away soil in one spot and look for the seed. If it has sprouted but not reached the surface, it was likely planted too deep. If it has not sprouted at all, the soil may be too cold, too dry or too wet, or the seed may be old. The seed quantity calculator explains germination rates and how to test old seed.
Sowing depth in summer and fall
Seeds sown in midsummer for fall crops face hot, dry soil at the surface. A few adjustments help:
- Sow at the deeper end of the range, where the soil stays cooler and moister.
- Water the furrow before sowing, then cover the seed and water gently again.
- Shade the row with a board, burlap or shade cloth until seedlings emerge, checking daily and removing the cover as soon as they appear.
- Sow in the evening so seeds start in cooler conditions.
Lettuce and spinach in particular germinate poorly in hot soil. Sowing them in a shaded spot, or starting them indoors and transplanting, often works better in summer.
What to cover seeds with
The material over your seeds matters almost as much as the depth.
- Fine garden soil: works well in loose, crumbly beds. Break up clods first.
- Sifted compost: holds moisture and does not crust, a good choice over clay.
- Vermiculite: light, moisture-holding and lets some light through, ideal for small seeds indoors and outdoors.
- A board over the row: an old trick for carrots and parsnips, which are slow to germinate. Lay a board over the sown row to keep moisture in, and lift it the moment seedlings appear.
Depth by seed size at a glance
| Seed size | Example | Approximate depth |
|---|---|---|
| Dust-like | Some flower seeds | On the surface |
| Very small | Lettuce, carrot | ⅛ to ¼ in, barely covered |
| Small | Tomato, pepper, onion | About ¼ in |
| Medium | Beet, radish, spinach, cabbage | About ½ in |
| Large | Bean, pea, cucumber, squash | About 1 in |
| Very large | Corn kernels | About 1 to 1½ in |
Common planting depth mistakes
- Burying tiny seeds. Carrots and lettuce under half an inch of soil often fail to appear.
- Raking clods over seeds. Large clumps leave seeds unevenly deep and create air pockets. Use fine soil or compost to cover.
- Letting the surface dry out. Shallow seeds need steady moisture until they sprout. A light daily watering may be needed in warm weather.
- Planting strawberries too deep. A buried crown rots. Keep it level with the soil.
- Planting trees too deep. The root flare should sit at or just above soil level.
Frequently asked questions
How deep should I plant seeds?
A good rule is two to three times the width of the seed. Tiny seeds such as lettuce and carrots are barely covered, while large seeds such as beans and squash go about an inch deep.
What happens if you plant seeds too deep?
The seedling may use up its stored energy before reaching the surface and never emerge. Deep seeds also sit in cooler soil, which slows germination.
How deep do you plant tomato plants?
Deeper than they grew in the pot, up to the first set of true leaves. Tomato stems grow roots along the buried section, which makes plants sturdier.
How deep should I plant bean seeds?
About 1 inch deep in most soils, slightly deeper in light sandy soil and slightly shallower in heavy clay.
Do lettuce seeds need light to germinate?
Lettuce germinates better with some light, so sow it on the surface and barely cover it, then keep the surface moist until seedlings appear.
How deep do you plant potatoes?
About 4 inches deep, then hill soil or mulch up around the stems as they grow to keep developing tubers covered.
How deep do you plant carrot seeds?
About a quarter inch or less. Cover them with fine soil, compost or vermiculite, and keep the surface moist until they germinate, which can take two to three weeks.
Should I plant seeds deeper in summer?
Slightly. Sowing at the deeper end of the recommended range keeps seeds in cooler, moister soil. Watering the furrow first and shading the row also help.
How deep should I plant squash seeds?
About 1 inch deep. Plant two seeds per spot and thin to the stronger seedling once they have a couple of true leaves.
How deep do you plant onion sets?
Just deep enough that the pointed tip sits at or slightly below the soil surface, about an inch deep.
How deep do you plant garlic?
About 2 inches deep, measured to the base of the clove, with the pointed end up. Space cloves about 6 inches apart.
How deep should I plant corn?
About 1 to 1 1/2 inches deep, slightly deeper in light sandy soil. Plant in a block of several short rows for good pollination.
Does planting depth change for raised beds?
Not much. Raised bed mixes are loose and drain well, so use the standard depth, or slightly deeper in midsummer when the surface dries quickly.