How to Determine the Proper Depth to Plant Seeds
Planting at the right depth improves a seed’s chances
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Planting seeds at the right depth improves their chances of developing into hardy seedlings and increases germination rates. The precise depth varies depending on the size and type of the seeds you have. And while seed packets always provide a recommended seed depth, sometimes we lose the seed packet with all of its specific planting instructions, or we get some seeds from a friend, minus those helpful instructions. That’s when we need a way to figure out how deep to bury those seeds in the seed-starting mix or garden soil.
General Wisdom for Planting Depth
Although there are plenty of opinions on this, common gardening wisdom advises not to plant any seed deeper than twice its diameter. The classic “quarter-inch” planting depth found on many seed packets is too deep for many small seeds.
Information on Seed Company Websites
If you know which type of seeds you have, look for that seed variety on major seed company websites. Many sites include information about the best seed planting depth along with the descriptions of the seeds they sell. Even if you don’t know the specific variety of your seeds, you can still gain some insight reading about similar plants. For example, if your neighbor gifts you with some bush bean seeds, you can read about bush bean seeds of several varieties on a seed company website and make a good guess at the correct planting depth.
General Guidelines for Seed Depth
If you can’t find the recommended planting depth for your specific seeds online, here are a few tried-and-true guidelines you can follow:
- In general, seeds should be planted at a depth of two times the width, or diameter, of the seed. For example, if you have a seed that’s about 1/16 inch thick, it should be planted about 1/8 inch deep. Large bean seeds, which can be up to 1/2 inch wide, may need to be planted an inch deep.
- For tiny seeds, place them on the surface of the soil and barely cover them with soil or vermiculite.
- Don’t compress the soil atop the seeds as you plant them. The soil should be firm but not compacted.
Seeds to Cover With Soil
Most seeds, including most of the familiar vegetable and fruit seeds, require covering with soil:
- Brassicas (broccoli, cabbage, cauliflower)
Seeds That Should Not Be Covered
Some seeds need light to germinate. Simply place them on the surface of the soil and press them gently to ensure good contact with the soil. Do not cover them with soil. Most of these are tiny seeds, and only a few of them are popular for vegetable gardens. Some examples include:
- Ornamental peppers
- Sweet alyssum
Problems With Planting Too Deep
Large seeds are more tolerant of being planted too deep than tiny seeds are. Common effects of planting too deep include limited or failed germination and weak seedlings. If you have any of these problems with your seeds, double-check the recommended planting depth, or plant a little shallower the next time.
Planting a seed at the right depth improves the chances of developing a hardy seedling. Learn how to tell how deep is deep enough for planting.
Planting Calendar: When to Plant Vegetables
Enter your location above to get your spring and fall planting dates!
Vegetable Planting Calendar
Find out when to plant vegetables with the Almanac’s planting guide!
We’ll tell you the earliest dates to plant vegetables in the spring and the last dates that you can plant for a fall harvest, based on average frost dates for your location.
The gardening experts at The Old Farmer’s Almanac have done the homework for you! Our planting tool is personalized down to your zip code, pulling from a database of thousands of weather station reports, and using the “days until harvest” for the most popular vegetables grown in the home garden. Then, we determine when to sow indoors, transplant, and seed outdoors based on what’s best for each vegetable. (Note: Our chart takes into account the average “days until harvest” for the most common varieties of each vegetable. However, your seed packet will tell you the exact days to maturity for the variety you are growing. For spring planting dates, you can always calculate the planting dates yourself using our Frost Dates Calculator.)
For an autumn harvest, however, it’s a little more complicated, since you will need to harvest many vegetables before winter frosts begin. Our fall planting dates consider which crops are more hardy versus tender, and we’ve also made adjustments for the harvesting period. (If you find that the veggie or fruit you wish to grow doesn’t leave you enough days to harvest in the fall, perhaps you can find a special variety with a shorter growing season!)
Note: Frost dates are based on 30-year rolling averages, so they are only a guide of what is “typical.” Every year can be different. Also, every garden can have what we call “microclimates” (e.g., an area in the dip of a valley or on the slope of a mountain) which differ. You’ll need to use your best judgement and this guide as a good starting place. Over time, you’ll gain experience and learn what works best in your garden!
Spring and Fall Planting Guides
Our vegetable planting charts are not only personalized to your zip code, but are also printable so that you can take them with you! In case you missed it, look at the top of this page and enter your “City, State” or Zip Code in the field. (If you live in Canada, enter your “City, Province” or Postal Code.)
Lettuce seedlings. Photo by Surachet Khamsuk/Shutterstock.
Find the best dates for planting and transplanting vegetables and fruit! Our free planting guide calculates the best dates for sowing seeds indoors and outdoors, and for transplanting seedlings into the garden—all customized to your location. Based on frost dates and planting zones.