Do you ever find it frustrating that the most expensive part of starting seeds is… the dirt? Seed trays are cheap, heat mats are cheap, even high quality seeds are cheap! Don’t believe me? Here’s the actual cost breakdown from my most recent round of seed starting:
Which is why I used a single very large, very affordable bag of organic potting soil mix from the local hardware store to fill all my seed trays instead. I even have leftovers to use for grow bag projects. With plenty of experience skipping the pricey seed starting mix, I can happily pass on that the answer to our original question is “yes, you can absolutely use potting soil instead of seed starting mix to start seeds in trays.”
There is however no denying that seed starting mix does result in a notably higher germination rate. Luckily, we can close at least some of that gap cheaply and easily. Try these two strategies for improving your potting soil first before packing it in your seed trays.
Starting plants from seeds can be an affordable and rewarding way to grow beautiful flowers, tasty vegetables, and lush herbs While you can certainly purchase pre-made seed starting mix, potting soil is a much more budget-friendly alternative that works well for seed starting
In this comprehensive guide, we’ll cover everything you need to know as a beginner about using regular potting soil to start your seeds successfully, including
- The benefits and potential drawbacks of potting soil for seeds
- Tips for preparing and amending basic potting soil
- Recommended potting soils and what to look for
- Step-by-step instructions for seed starting with potting soil
- Troubleshooting common problems like damping off
The Benefits and Drawbacks of Potting Soil for Seeds
Basic potting soil can absolutely be used to start seeds in trays or containers. The main advantages are:
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Cost savings – Potting mixes are exponentially cheaper than specialty seed starting mix. A huge bag of potting soil can cost as little as $10-15 versus $30 for a small amount of seed start mix.
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Availability – Potting soil is readily available at most hardware stores, garden centers, and big box retailers year-round. Specialty mixes may be harder to source.
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Nutrients – Potting soil contains beneficial nutrients to help feed seedlings as they sprout and grow. Seed starting mixes do not.
However, standard potting soil also has some drawbacks to be aware of:
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Drainage – Potting mixes tend to retain more moisture than lightweight seed starting blends. This can lead to overwatering.
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Texture – Potting soils usually contain pieces of bark, perlite, etc. that can obstruct delicate seedlings. Seed start mix is screened to be smooth.
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Compaction – Potting soil compressed over time can inhibit seedling root growth. Seed start mixes are loose and fluffy.
Luckily, there are some easy fixes to help mitigate these issues and turn basic potting soil into an effective seed starting medium.
Preparing and Amending Potting Soil for Seeds
With a couple simple preparation steps, basic potting soil can work just as well as pricey seed starting blends:
Sift Out Large Particles
It’s important to sift out any large chunks of bark, perlite, vermiculite, or peat from potting soil before using it for seeds. An old colander or sieve works great for this. Anything leftover can be mixed back into outdoor garden beds.
Mix in Coir or Vermiculite
Adding porous amendments like coco coir or vermiculite to sifted potting soil helps retain the light, fluffy texture that seedlings need.
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Coco coir also helps prevent compaction and improves drainage. Aim for 25% cocco coir to 75% potting soil.
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Vermiculite improves moisture retention. Use approximately 10-15% amendment by volume.
Loosen and Fluff
Make sure the amended potting soil is nice and loose before filling seed trays or pots. Break up any clumps and fluff it up with your hands or a tool.
Follow these simple steps, and basic potting soil will work great for starting all kinds of seeds!
Recommended Potting Soils for Seed Starting
When purchasing a basic potting soil for seeds, look for:
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Organic or natural – Avoid chemical fertilizers and synthetic ingredients.
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General purpose or all-purpose – Avoid specialized mixes like cactus soil.
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Coarse texture – Fine, lightweight mixes are easier to sift.
Some good options include:
- Miracle-Gro Indoor/Outdoor Potting Mix
- Espoma Organic Potting Mix
- Vigoro All Purpose Potting Soil
Avoid moisture control or water retaining potting soils as they can stay too wet.
Step-By-Step Guide to Starting Seeds in Potting Soil
Follow these simple steps for success using prepared potting soil to start your seeds:
1. Fill Seed Trays or Containers
Fill seed trays or starter pots nearly to the top with prepared, loose potting soil. Gently firm it down to remove air pockets.
2. Plant Seeds
Follow the planting depth and spacing guidelines on the seed packets. Gently water after planting to settle the soil.
3. Cover and Water
Place seed trays in a warm area or use a heat mat. Cover trays with plastic dome lids or plastic wrap to retain moisture. Keep soil moist but not soaked.
4. Uncover After Sprouting
Once sprouts emerge, remove covers and ensure they receive plenty of light. Allow the soil to dry out slightly between waterings.
5. Transplant Seedlings
Carefully transplant sprouts into larger containers or the garden once they develop true leaves. Harden off plants first.
Troubleshooting Common Seed Starting Problems
Even with the ideal soil mix, you may encounter some issues when starting seeds. Here are some common problems and fixes:
Seeds not sprouting – Ensure seeds are not planted too deep. Maintain warm soil temperatures and consistent moisture. Scarify extra hard seeds.
Damping off – Fungus caused by overly wet soil. Allow soil to dry out more between waterings. Improve drainage and air circulation.
Leggy seedlings – Lack of light causes excessive stem growth. Provide 14-16 hours of daily light or supplement with grow lights.
Wilting – Could indicate underwatering, transplant shock, or disease. Check soil moisture and remedy based on cause. Hardening off helps prevent transplant wilting.
Slow growth – Cool temps, lack of nutrients, or root problems could be the cause. Try re-potting in fresh soil and provide better growing conditions.
With the right preparation and care, seed starting in potting soil can be easy, affordable, and very rewarding! Follow this guide and you’ll be on your way to growing beautiful, healthy seedlings.
Sift Your Potting Mix#
The biggest issue with potting mix for seed starting is the presence of larger materials that will obstruct your seedlings. Sticks aren’t an appropriate substrate if the goal is to maximize germination, which is why seed starting mixes are made of much, much finer soil particles.
To fix the issue, grab a coarse kitchen strainer, some hardware cloth, a section of poultry fence, or even a colander with large holes and sift the potting soil first. I’m always a little shocked at how effective this is at creating a finer mix for my seed trays with 30 seconds effort. Don’t forget to reuse the wood chips and other larger materials as mulch or fodder for the compost heap.
We Tested 8 Seed Starting Mixes, Here’s What We Learned
FAQ
Can I use potting soil for seed starting?
Most good quality potting soils work great for starting seeds, IMO they work even better than seed mixes because they provide nutrition to the seedling, you just need to make sure it’s not a chunky mix and that the fertilizers aren’t too strong which can burn sensitive seedlings.
What potting mix to use for seeds?
Instead, choose a high-quality seed-starting mix that is well-draining and nutrient-rich. The mix won’t contain any soil, but is made of light, fluffy materials such as peat moss, vermiculite, perlite, coconut coir, and rice hulls that provide the ideal base for seeds to germinate and grow.
What type of soil should I start my seeds in?
the “best soil” for seedlings is your normal potting soil with a bit of perlite mixed in and watered with dilute starter fertilizer, under a humidity hood, on a heat mat, and under bright but not overly intense light.
Is it okay to start seeds in Miracle-Gro potting soil?
Seed starting medium needs to be very fine (ie few chunks of bark etc.) and have no added chemical fertilizers. Miracle Gro potting mix is not ideal. You’d be better off getting proper seed sowing mix, especially if seeds are small.