Now for the fun part – Let’s get some seeds in the dirt!
This is Part 3 of the Guide to Seed Starting series. Catch the rest of the series here:
WHEN and WHAT to plant: Part 1
SUPPLIES: Part 2
SEEDLING CARE and TRANSPLANTING: Part 4
Fill your seed-starting containers
[Referring to our list from Part 2] Grab your seed-starting flat (or other containers), your soil medium, your seeds, your labels and an ever-reliable permanent marker. Spread out in an area you don’t mind a bit of dirt. We’re about to fill that flat with soil. It’s the moment when the heavens open up and I hear angels singing. I have gone months without that smell of dirt and that smell just goes right to my soul. It feels good and right to run my fingers through the dirt, my friends. As excited as I am by this activity, filling the flat is a good kid job, so ok, I reluctantly let them do this part.
You want the soil to be moist, so if it is dry, mix in enough water. When covering your seed flat, make sure to lightly tamp the soil down to the bottom of the cells to get the deepest possible block for those roots.
Lay the seeds out
Many gardeners put a couple seeds in each cell to account for a less than 100% germination rate. If both germinate, you can pull the smaller of the two, eat it, compost it, or painstakingly divide it as I’m prone to do.
The act of laying the seed out is where it’s important to have a planting method and your labels handy. Are you going to lay out seed left to right in short rows? Long rows? Are you going to work in 6-cell blocks? Most home gardeners aren’t going to have an entire flat of one variety, so it’s important to decide on something organized, or you’ll quickly get confused over what’s what. It’s especially necessary to keep your seeds straight when planting multiple varieties of the same plant type. You won’t forget this after you accidentally plant the habanero pepper in the kids snacking garden!
Cover your seeds lightly with soil, and do not pack it down. Seeds should not be planted deeper than twice their diameter. In other words, tiny seeds need barely any covering, whereas some large bean seeds can sit an inch down when you direct sow them.
Clearly label each plant variety within the cell flat. I also like to keep a record on Tended App of what varieties I have planted, and where. I can actually sketch out my seed flat and put my plantings on there – five rows of Amish Paste Tomatoes, one row of Joe’s Long Cayenne Pepper, etc. This is really handy because my seed starts get shuffled around quite a bit as some germinate faster than others, some need to get off the heat mat, or are transplanted to larger containers.
As I mentioned in Part 2, different seeds germinate best at different temperatures. If you love growing lots of tomatoes, but your house is cold like mine, you probably purchased a germination heat mat. This handy chart will guide you in which plants to use that for, and what to set your temperature controller to.
Bring your seed flat over to your grow light area. Double check that the soil is plenty moist. If it needs more moisture, spray the soil surface with a spray bottle. This gentle method is less likely to disturb your tiny seeds. Next, cap the tray with your humidity dome, if using. Set it on your heat mat, if using.
It’s pretty safe to say that vegetable seeds do not need light to germinate, so wait to turn on your grow light until those seeds sprout. If you’re getting into flowers, you will want to check specific instructions for those, as some need light to germinate.
Peek in on your tray daily. A little poke of the soil surface will indicate whether the tray needs another spray down with your water bottle. Folks, this waiting-for-germination-part takes patience! Some seeds take a really long time to germinate, and all of them take different amounts of time. I always love to sprout mustard seeds, even if I don’t need more than what comes back in my garden, because they’re super speedy! Patience will reward you, though. If you’re becoming filled with doubt and want to check, a chart like this one can tell you the approximate number of days until your seeds should germinate.
Once your seeds germinate, turn off any heat mats and turn on the grow lights. It’s important to place the grow light just a couple inches from the top of the plants to avoid legginess in the plants. As the plants grow taller, just raise the light with them. The plants need about 12 hours of light each day, so be sure to shut your lights off regularly, or put them on a timer. You’ll also want to check daily that the soil is moist. We like to add water to the bottom drainage tray so that the plants can suck the water up from the bottom, encouraging deeper root growth.
Cheers to growing your food from seed, all!
In the next and last part of this series, I’ll cover continued care for the seedlings, including transplanting.