Now that we've got your seed starter mix ready to go, here's my best advice for avoiding all-too-common pitfalls for more reliable seed germination results!
Getting the moisture right
After you’ve mixed and blended your seed starter mix well-- it's time to moisten it to the appropriate level of dampness. Use warm water! This will makes the seed starting process more comfortable for your seeds—and you!
A 5 gallon pail with a lid works well for this step. Add water, close the lid of the pail, and give the water some time to soak in. If your mixture is dry, it will tend to repel the water at first.
A 5-gallon pail with a lid filled with pre-moistened seed starting mix
As your mix gains moisture, it will readily absorb more water. Moisten the mix a little at a time, cover, give it time to absorb, fasten the lid, and shake to remix. (A pail filled about 2/3 full will allow enough space to mix well.) Check the moisture level and if needed, add more moisture and repeat the process. Keep adding moisture until your mix is damp but not sodden.
After each addition of water, allow the moisture to thoroughly absorb, and remix your starter mix to make sure the moisture is distributed evenly throughout. You want your mix moist enough to flow, without dusting, but dry enough so that it doesn't clump or smear as you working with it.
Excess moisture can lead to seed rot and fungal issues. If it smears or clumps even after mixing add more premixed dry ingredients at the same 10 to 3 ratio—a little at a time and mix in. Or if you just need to amend it slightly, add a little more vermiculite to absorb the excess.
Remove air pockets in your seed trays
Now you’re ready to fill your seed trays or containers with your pre-moistened seed starter mix. Start by mounding the soil in the middle and use your hands or a straight edge to spread the starter mix across the cells and to the corners, so each cell is level full. Screed any excess back into your wheelbarrow or pail with straight edge or ruler.
Gently tap the tray on the table to settle the soil in each cell and eliminate any air pockets. Placing the tray into it’s nesting tray and tapping the whole set on the table works well. This is important—air pockets are a problem! Roots grow in soil; more soil, more roots, more nutrients, more growth.
After tapping to settle the soil mix well, there should be enough space at the top for planting seeds. If any cells had obvious air pockets and settled a lot, grab an old spoon (a handy tool for this process) and just add enough starter mix to those cells as needed. Tap on the side of that cell to resettle the soil mix.
Next make a small indent in the surface before you sow your seeds. I like to use my finger. You can use the bottom tip of a marker or the eraser end of a pencil-- they also work well for this. Make small indentations in the mix for each seed according to the planting depth recommended for the specific plant variety.
Using my fingers to make indentations for seed sowing
Only start what you NEED to start
Before you plant-- double-check. Ask yourself: "Do these seeds NEED to be started ahead of time?" There are many seeds that we do NOT recommend you start, including beans, cucumbers, squash, zucchini, pumpkins, corn, melons, and watermelon for example.You COULD start them indoors but in our experience they don't transplant all that well.
The transplant shock can easily erase any time you gained in starting them ahead of time. And the plants may not ever fully recover and be all that they could have been-- IF they had been direct seeded.
And in the meantime-- you've wasted a lot of time and energy that could have been invested in starting other more needy seedlings. None of us need to add unnecessary tasks to the load!
Follow those planting instructions
Plant your seeds according to the instructions on the seed packet. Surface sowing for seeds that need light to germinate. OR covering them with a thin layer of the seed starter mix to the depth needed.
Surface sown seeds should lay right on the surface of the soil. For seeds that need to be planted at a depth with a layer of soil covering them-- as a general rule of thumb, sow at a depth of about 2x their diameter. For instance, if a seed is 1/8 of an inch in diameter, plant it at 1/4 inch deep.
Large seeds are pretty easy-- I like to place them on the surface and use the eraser end of a pencil to press down to the desired depth. The pencil method makes it easy to judge how deep you're getting the seeds and helps you set the seeds at the same depth across all the cells. The more even the depth, the more evenly they'll emerge!
For smaller seeds use the 'pinch and roll' method. Pour some seeds from the packet into one hand, pinch some seeds between the thumb and pointer finger, roll them between your fingers, and drop the seeds into each indented cell. Then just cover them to the desired depth.
If the seeds are not round or are super tiny—like lettuce, oregano, spearmint, or rudbekia-- take a toothpick, wet the tip on your tongue—just a little. Now pick up one seed with the wet tip and place it in the indented cell. So easy to place ‘em right where you want ‘em! The tinier the seeds, the more shallow the depth of planting.
We usually plant at least 3-5 seeds per cell. The seedlings should all germinate together and help each other push up through the soil above.
Planting 3-4 seeds per cell
In addition, having some competition will help you identify the less vigorous seedlings, so you can prioritize the best seedlings to transplant-- saving that precious space under your grow lights AND in your garden for the most vigorous plants.
After sowing your seeds, gently press on the soil surface to ensure good soil to seed contact. This is essential for good germination.
For surface sown seeds that need light to germinate—after laying them on the soil surface, gently press them into the soil without burying them. Again—making good soil to seed contact.
Gently mist the surface lightly with water to settle the seeds in place while moistening that critical surface area. Moist and settled but not soggy! Now we watch for germination!
Maintain moisture levels
Uneven watering is another big barrier to successful germination. To encourage germination, ensuring consistent moisture levels throughout the germination process.
Our strategy is to cover our trays with a layer of window film-- the kind you use inside the house and shrink down with a blow dryer. This has worked well for us and we’ve been reusing this plastic film for years!
Covering with plastic film to prevent drying out
Covering your trays keeps them from drying out. The most common reason for failure in the germination process is the trays are either too dry or too wet. If you’re keeping your trays from drying out, you shouldn’t need to rewater prior to germination.
Monitor your seedlings closely as you await germination. Once you see seedlings lifting the soil and any emerging—get those little babies under the grow lights! (More on that next time-- so stay tuned!)
We like to germinate our seedlings on our dining room table—where we can keep a constant eye on them. (Since Easter is early this year we’ll start seeding afterwards and using the dining room table won’t be an issue.)
Temperature notes
Pay attention to optimal temperatures for germination. Some seeds germinate best at cooler temps. Others, such as peppers, like it warmer. For most seeds, room temperatures are just perfect.
Indoor temps mean heat mats are rarely needed! Do not use a heat mat unless you absolutely need to use one to reach the optimal germination temperature.
See our germination charts for veggies here and for flowers and herbs here. These will give you the information on days to germination and optimal germination temperatures-- critical to your success! (For more information on how to use these charts, read our blog post, "3 Simple Steps and a FREE Download To Plan Your Garden in 2024.")
Heat mats will cause your trays to dry out much more quickly. As I said earlier, drying out is one of the biggest barriers to success when trying to get your seeds to germinate. Heat mats literally drive the moisture out of your trays before the seedling emerge. That means you will likely have to water before emergence.
If you MUST water before emergence, water using a bottom tray-- watering from below as needed. Remember, damp not soggy!
We'll talk about grow lights and more next time! 😎 Happy seed starting adventures! 🫘🌱🌿
Your garden coach,
Theresa