Cheat Sheet for Planting Seeds

A tray of peat pots with a variety of herb and vegetable seedlings.
My Garden Life
February 26, 2024
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If you’re like most gardeners, by March you have already placed a big seed order or are lucky enough to have those glossy packets of joy already in your possession. The last frost dates in the United States are usually some time after April (depending on your location), so now is the time to do your homework on how to plant your seeds efficiently for the best possible results.

There are a variety of methods to consider when planting seeds. Different methods include simple scattering, finger holes, and seed mounds. However, before you get to plant, you need to know when to plant and how deep to place the seeds.

Follow the Seed Packet Instructions

In most cases, the best way to sow or plant seeds is by following the instructions on the back of the seed packet but there are a few things to keep in mind beyond the information on the seed packet.

One thing to remember is that not all seeds will germinate, so even if you space things exactly as suggested in the diagrams on the back of the seed packet, odds are you will have empty areas in your layout when a seed fails to germinate.

You may also be asked to plant two or three seeds in a hole, to make sure at least one will germinate, but then you will have to pull the other two if they do germinate.

A small mound of soil with four squash seedlings emerging.

Perhaps the most important thing to know from the seed packet is when to plant the seed. Some seeds are best planted in cooler weather and others after the warmth has finally arrived. Other than that, you can use some simple rules of thumb for planting depth and spacing so that if ever a friendly gardener just hands you a Ziploc of spare seeds, you can do what needs to be done even without written instructions and still get good results!

The Golden Rule of Seed Planting Depth

This is an easy rule of thumb to remember: plant a seed at three times the depth, as it is in size.

A woman making holes in the soil of a planting tray preparing spots for planting seeds.

How to Sow Small Seeds

Small seeds like lettuce or many types of flower seeds don’t actually have to be planted at all since they are so small. Here are the steps for planting small seeds:

  • Premoisten the soil you will be planting in.
  • Scatter the seeds on the surface of the pre-moistened soil.
  • Sift a fine covering of lose dirt on top and lightly tamp down with your fingers.

By pre-moistening the soil, instead of watering afterwards, you keep the seeds from getting disturbed with water runoff before they’ve had a chance to germinate. This scatter method works great for small flower or herb seeds that you plant in spring or fall. The seeds are so minute that it would make little sense to sit and make tiny holes to put exactly three seeds in each.

A woman planting seeds in a plastic seed tray on a wooden table.

Once the seedling have started developing their true leaves you can thin out any extra or feeble seedlings to allow those remaining to thrive. You can also try transplanting the extra seedlings and use them to fill in other areas in your garden later.

How Deep Should You Plant Medium-sized Seeds?

Tomato and pepper seeds aren’t diminutive, but they aren’t large either. Seeds that aren’t tiny or large can still follow the golden rule for planting. These seeds need more soil contact and so should not be sown using a scatter method. Instead, use the finger method to plant your medium-sized seeds. Look at how big the seed is and then stick your finger in the dirt to a depth three times the size of the seed. Space according to how big the plant grows giving space on either side.  Put two or three seeds in each hole, cover, and water. If more than one seed germinates in each hole you’ll want to pluck out the extra.

A finger with a tomato seed on the tip getting ready to be planting in a tray of soil.

Planting Large Seeds

Large seeds like squash and corn can be planted directly outside either by planting in a hole or creating small mounds of dirt. These mounds can hold two or three seeds that are spaced a few inches apart from each other, instead of having them all in one hole.

If the seeds are slightly older, you may be expecting a lower germination rate; in that case, you can try planting two or three seeds in each mound or hole. Keep in mind you will need to pull out extra plants out if they do grow after all.

Use your finger to size the hole three times as deep as the size of the seed.

Close up of a hand planting a large seed in a small mound of garden soil.

Large seed mounds end up being spaced very far apart from each other to give the plant proper space to grow (refer to the seed packet for suggested plant spacing). So if you plant one squash mound with three seeds in a triangle shape the next mound could end up being two or three feet away. That’s because plants like corn, or sprawling vines like squash and melons, need room to grow and space to allow proper wind currents to assist with pollination.

Other Methods for Planting Seeds

If the methods mentioned above seem too messy and arbitrary, there are plenty of other methods that can appeal to more tidy gardeners. If you think you want a more refined approach to seed planting, take a look at some of these options.

Square Foot Planting

There is an entire science to measuring the spacing between plants and how many seeds to plant in a row that you can use called “Square Foot Gardening.” The author of the original square-foot planting schemes is Mel Bartholomew and he has several books out that give specific guidelines. Be prepared to lay out beds in square foot patterns complete with guide strings. This type of planting is very efficient and can produce large yields, but takes some study to set things up properly.

A wood raised garden bed with strings dividing it into square foot plots with different vegetables planted in each square.

Starting Seeds on Your Windowsill

Small greenhouse kits are available in any home and garden store at the start of spring. The kits make it easy to germinate your seeds in special expandable peat pellets and the process is both fun to do and interesting to observe as plants grow.

You will need a sunny window to put the miniature greenhouse by, preferably South-facing.

A seed-starting kit is a neat gardener’s dream as the peat keeps the seed encased without dirt going everywhere during the germination process. Once germinated, you will have to transplant once the weather gets warm enough for seedlings to survive.

A woman using a seed starting kit with peat pellets in a tray for planting seeds.

If you do go this route, don’t forget to “harden off” the plants by gradually exposing them to the outdoors a few hours at a time over a period of a few days before finally planting them outdoors. This will help them to get used to the harsher weather outside once they are moved from the climate-controlled area indoors.

Starting Seeds Using Seed Tape

If you have a larger garden you might like the neatness and efficiency of seed tape. Seed tapes are essentially a ribbon-like strip of biodegradable paper with the seeds already adhered to the tape and pre-spaced the optimum distance for good plant growth. All you need to do is create a channel in the soil at the proper depth for the seeds being planted, lay down the strip of seed tape, cover with soil, and water.

A close up of a hand holding a seed starting tape with bright green planter boxes with seedlings in the background.

Make Your Own Seed Tape

If you can’t find a seed tape with the type of seed you want, you can create your own. Rolls of adhesive, water-soluble tape are available for purchase. You just stick the seeds to the tape, spaced at the distance recommended on your seed packet and plant just as you would prepared seed tape.

You can also use a swath of toilet paper and place the seeds along the middle of the strip and line them up down the length of the toilet paper. Dab the seeds with water before placing them down to get them to stick. Fold over the outer edges of the toilet paper to the middle to cover the seeds and you have a do-it-yourself seed tape that can be planted right away.

Don’t make these seed tapes ahead of time, as the dab of water and toilet paper can start the seed germinating if left alone for a few days. Also, avoid using super-plush brands or those that contain lotions or perfumes – basic is better.

A woman wearing red garden gloves planting rows of seed tape in garden soil.

Jumpstart Seed Germination

Some seeds are slower to germinate than others. It is possible to give your seeds a jumpstart to germination by manipulating light, water, or temperature conditions. See our article, Tips for Seed Germination to learn more about how you can give some seeds a head start.  

Saving Seeds from Year to Year

If you end up with more seeds than you can use, you can store them for a year or two. Seed viability will diminish over time, so it’s important to store seed properly and try to use it the following season. Another option is to share your extra seeds with others. A fun way to do this is by creating your own seed packets and giving them your personal touch! Learn more in our article, Make Your Own Envelopes for Saving Seeds.

Rustic wood table with homemade seed packets and different seeds spilled out onto the table.

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