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Have you ever run into this problem while growing vegetables: how deep should you plant the seeds?
If you plant them too shallow, they might dry out or get blown away. But if you bury them too deep, they might not come up at all.
Does planting the same vegetable seed at different depths actually make a difference? Will it really affect how well they sprout or how they grow later on?
Recently, I came across a very experienced gardening blogger who did a super detailed experiment that answers these exact questions—something many of us wonder about.
He tested several common vegetable seeds—like arugula, lettuce, tomato, pea, cucumber, and pumpkin—by planting them at different depths, from surface sowing to burying them as deep as 3 inches (about 7.5 cm). Then he observed how they sprouted and how they grew over time.
He shared the entire process and results in detail, and I found it really helpful. And I’ve organized the key points here, and I think it’s a great learning opportunity for all of us!
Arugula and lettuce seeds are very tiny, and these two veggies sprouted best when planted shallow. Whether the seeds were sprinkled right on the soil surface or lightly covered with less than half an inch (about 1 cm) of soil, they had a high germination rate and the seedlings looked healthy.
But when I planted them deeper—between 1 to 3 inches—almost none of them sprouted. This shows clearly that small seeds need to stay close to the soil surface. They just don’t have enough energy to push through a thick layer of soil.
Tomato seeds are medium-sized, and they did well when planted anywhere from surface level to about 1 inch deep. The seedlings came up evenly, and the stems were strong.
But when I planted them 2 to 3 inches deep, fewer seeds sprouted, and the ones that did looked weak. Some didn’t even make it out of the soil.
So, if you’re planting tomatoes, it’s best to sow the seeds about ½ inch to 1 inch (1–2.5 cm) deep.
This gives you good sprouting and healthy, strong plants.
Pea seeds are quite large. At first, I thought planting them shallow would help them sprout faster—but the results surprised me. While shallow-planted peas did sprout, the seedlings were weak: thin stems, easy to fall over.
When I planted them deeper—2 to 3 inches—the seedlings were totally different. They had thick, strong stems, stood upright, and had bigger, healthier leaves.
This shows that large seeds like peas grow stronger when planted deeper in the soil. Deep planting is definitely better for them.
Pea seeds are quite large. At first, I thought planting them shallow would help them sprout faster—but the results surprised me. While shallow-planted peas did sprout, the seedlings were weak: thin stems, easy to fall over.
When I planted them deeper—2 to 3 inches—the seedlings were totally different. They had thick, strong stems, stood upright, and had bigger, healthier leaves.
This shows that large seeds like peas grow stronger when planted deeper in the soil. Deep planting is definitely better for them.
Here is a summary of how six common vegetables performed when planted at different depths:
Seed Type | Recommended Sowing Depth | Effect of Sowing Depth on Germination and Growth |
Arugula | Broadcast or very shallow (<0.5 inch) | The shallower the better; depth >0.5 inch severely hinders germination. |
Sallad | Broadcast or shallow (0.25–0.5 inch) | Fastest germination with broadcasting; depth >0.5 inch leads to poor or no sprouting. |
Tomat | 0.5–1 inchc | Adaptable; 1 inch is safest. Too shallow results in uneven germination. |
Pea | 1–2 inches | Best results at 1–2 inches. Too shallow dries out easily; 3 inches still germinates but takes longer. |
Gurka | 1 inch | Too shallow lowers germination rate; 2 inches slows it down, and 3 inches mostly fails. |
Pumpkin | 1–2 inches | Similar to cucumber; 1–2 inches ideal, 3 inches almost no germination. |
This experiment clearly shows that seed planting depth has a significant effect on plant growth. For those who want strong seedlings and to avoid issues like disease or weak growth, choosing the right planting depth is more important than we might think.
Small seeds (like arugula and lettuce) do best when surface-sown or very shallow; too deep and they struggle to sprout.
Medium seeds (like tomato) are more adaptable but planting about 1 inch deep is safest.
Large seeds (peas, cucumbers, pumpkins) prefer planting deeper (1–2 inches) to maintain moisture and stability, but not deeper than 3 inches, as most won’t emerge well beyond that.
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