One inch, two inches? How important is it to get the spacing and depth just right when planting seeds? Seed packets usually have instructions, sometimes detailed, sometimes vague, about spacing and depth, but it isn’t always all inclusive, and gardeners can get a bit more worried about it than they should. Seed spacing and seed depth are the two variables, and the matter in different ways. Fortunately, a few easy tricks will have you close enough without a measuring tape or depth gauge.

Seed spacing requirements are guidelines meant to help with two things: ensuring the seedling has enough room to begin growing, and reducing the amount of thinning you’ll eventually need to do. While planting depth will affect sprouting, seed spacing will not. To illustrate that spacing won’t affect germination, consider the common germination test we perform on seeds to test viability. We shake out a dozen seeds onto a moist paper towel, fold the towel over, put it in a plastic bag, seal it, and set it aside. The seeds sprout even when they are so close they touch. To germinate, seeds need only the right conditions, not elbow room.  

We space seeds based on their need for a bit of space and airflow after popping up and spreading their first leaves, called cotyledons, and to be able to easily separate them for transplanting. We can also space seeds out to reduce the amount of thinning we need to do as they grow, saving on seed. 

Spacing requirements are sometimes given as a space between seeds, meant to ensure room for early growth, and sometimes as a space between plants, meant to ensure room for mature plants to flourish. If the packet gives instructions for spacing and later thinning, then the initial spacing is for the seeds.

Example 1: Plant carrot seeds an inch apart. Thin to one plant every 2-3 inches after they’ve started to grow (bonus tip: wait a bit until the thinned baby carrots are pencil-sized for great snacking). 

Example 2: Howden pumpkin seeds are typically planted in hills 3-4 feet apart, with 5 seeds per hill, and are thinned to keep only the strongest two seedlings after they sprout. If planting them in a row, you might plant seeds one foot apart, and then thin them to 3-4 feet apart after their first true leaves show. Some may not germinate, others may get eaten by a critter, so planting extra makes sense.

Easy seed spacing references to use

Planting seeds at the desired spacing doesn’t mean you need to break out yardsticks or tape measures or get a helper. These simple tricks will have you properly spacing seeds in short order.

How wide is your finger?

Grab the ruler and check how wide your index finger is, and then the index and middle fingers together. Don’t press down to make it wider, since you won’t do that when planting. My index finger is ¾ of an inch wide, and the two together are an inch and a half, which makes a nice seed spacing measurement. 

Measure your hand

Again, we can measure our hand and use it as a handy seed-spacing tool. My hand, across the knuckles, is about four inches wide. It is also eight inches long from the tip of my index finger to the base of my hand. Planting sweet corn 8-9 inches apart and an inch deep gets easy now. Poke holes one hand length apart and one finger joint deep, and in go the seeds. Remember, seed spacing is approximate. If your hand is seven inches, just add a bit of fudge factor on each.

Use your garden trowel, Hori Hori, the seed packet, or other handy items

My favorite garden hand tool is my soil knife, also called a Hori Hori, and I typically have it with me in the garden. Many are marked with depths up to six inches, but by laying the tool on the soil, it also serves as a length measurement for spacing. Measure your seed packet (most Seeds ‘N Such packets are 3.25 inches wide by  4.75 inches long, making a handy measure for either three or five inch spacing), your garden trowel, or the pencil you stuck behind your ear for a quick spacing guide.

Make a custom layout tool

This sounds hard, but it isn't, and if you have a lot of seeds to plant, it can be a time saver. A scrap of wood, a piece of PVC pipe, or really anything a few feet long makes an excellent custom seed spacing marker. Layout a couple of common seed spacing dimensions and mark them along the tool using different colors. 

For example, if using a long scrap of wood, make marks at two-inch intervals with a red marker, and along six-inch intervals with a blue marker, or whatever dimensions you most often use. You won’t have to count or do math, just drop seeds at the right color marks.

Seed tapes

Not every seed is available on a seed tape, but those that are make proper spacing as simple as possible. Just cut off a length of the paper-based seed tape and bury it at the appropriate depth. 

Getting Planting Depth Right

With the exception of those few seeds that need light to germinate, the depth at which we plant seeds is driven primarily by the energy the seed has stored inside and how far that energy can propel a sprout to the surface, where it can begin harvesting sunlight. 

As a rule, small seeds store less energy, produce smaller sprouts, and are planted more shallowly. Large seeds like peas or corn store a lot of energy, produce stout sprouts, and can push up through an inch or two of soil with ease. All else being equal, a seed planted more deeply has a better chance to avoid predation by birds or dehydration of the seedling in the top crust of soil, but not all seeds can survive a deep planting. 

Following recommended seed planting depths is important, but it doesn’t require a precision measuring tool. Here are a few common seed depth terms, and how to easily achieve them.

Surface sow

These seeds usually need light, or are so very small that being buried in soil will keep them from popping through. Snapdragons are a perfect example. Scatter these seeds across the surface, then lightly press them into the soil with the flat of your hand to ensure good seed-to-soil contact. You can lightly dust them with fine vermiculite or very fine dry soil to keep them from blowing away, but don’t completely block the light from reaching them. 

Sow ⅛  to ¼ inch deep

This is a very common depth recommendation for small seeds like poppies, peppers, tomatoes, lettuces, and other tiny seeds. When sowing seeds indoors in cell packs, I drop the seed (or two) onto the surface of each cell, then use a toothpick to gently push the seed down a quarter inch, rather than trying to make a shallow hole and fill it. In the garden or in a seed flat, I’ll space the seeds out and then simply cover them with a quarter inch of soil instead of making individual troughs or holes. 

Sow ½ inch deep

Some melons, pumpkins, and other moderately sized seeds are recommended for planting at this depth. On my index finger, half an inch is the depth from the tip of my fingernail to the quick, so if I poke a hole just over that, and then drop the seed in, I’ve got it about right. 

If planting in a row, I’ll drag my finger down the smoothed soil to make a shallow trench about that deep. Then I drop the seeds in and just make a lobster claw motion with my hand to pinch the soil back over the seeds when I’m done. A firm patting down and they’re all set. 

Sow 1 to 1.5 inches deep

Peas, beans, and corn are good examples of large seeds that are planted an inch deep. For my finger, an inch is the distance from the tip of my finger to my first finger joint. Grab a ruler and check yours, and you’ll have a calibrated tool for planting seeds an inch deep. Some seed dibblers also have markings for an inch in depth, and that’s about the minimum depth I find a dibbler useful for.  

Remember, seed depth is more important than getting the spacing exactly right. Spacing is still important, but not critical. If you get them a little too tight, you’ll need to thin out more plants; if they're a bit too distant, you’ll waste a bit of space. No reason to worry. Find a handy approximation for the right spacing (like your finger) and get planting!