The start of spring is, mercifully, right around the corner, which means gardening season is upon us. For those of us who don’t live in reliably warmer climes, though, the end of winter doesn’t necessarily mean the end of the occasional cold snap. So, let’s talk about how to start your seeds off indoors—think of it as a few weeks of sheltering in place for your plants to be.
So-called indirect sowing offers some advantages when compared to the outdoor alternative (known as—surprise!—“direct sowing”) since it allows for better control of the environment during those first few crucial weeks when the plants are particularly fragile and the weather is reliably fickle. The drawback, of course, is that you’ll eventually have to move your plants outside, a process that takes time and comes with its own risks. But don’t worry, we have tips for when that time comes, too.
When to Start
Every plant is different, but, typically, you’ll want to start your seeds indoors about six weeks before the expected last frost in your area. The exact start date will depend on a number of factors—what exactly you’re growing and where you’re growing it, chief among them—so it’s best to consult a professional planting calendar. The Old Farmer’s Almanac has a free, interactive one that can get you started.
What You’ll Need
You’ll need the seeds, obviously, but also a container to plant them in, some seed-starting mix to put in that container and plastic wrap to put over it. You might also want to buy a heat mat to set that container on and a grow light to hang above it all.
There is a variety of container options from which to choose—anything a few inches deep with drainage holes should work fine. If you’re thrifty, you can clean out an old plastic food container such as a yogurt cup or grab an empty egg carton; just don’t forget to make a few holes in the bottom for drainage. You can also buy a standard container from the store or opt for a seed flat or tray, which tend to work better for particularly small seeds.
You’ll want to avoid using standard potting soil—while it will do the job for a full-grown plant, it can be too dense for seeds and seedlings. Starting mix will allow for better drainage and is specially formulated to avoid pathogens that can be deadly in a plant’s early stages of life. (It’s possible to make your own seed-starting mix, but if you’re just starting out, it’s best to just buy a bag from your local gardening store.)
Whether you need a grow light or not depends on the plant and where you’re keeping it. Many vegetables, for instance, need about eight hours of light a day—so, if you don’t have a window in your home that gets a lot of reliable sunshine, you may need to invest in a light. Meanwhile, heat mats can help keep your seeds warm as they germinate, especially if the temperature in your house is on the cooler side.
First, double and triple check that your containers are clean and have drainage holes. You’ll also want to keep your seed packets handy, as they can contain special directions unique to each plant. OK, now you’re ready to plant.
Step 1: Hand-pack your clean containers with seed-starting mix.
Step 2: Make a shallow depression with your finger for the seed. Plant it at the depth recommended on the seed packet, typically about a half-inch down. You can use your fingers for this part or opt for the eraser-end of a pencil or similar object.
Step 3: Sprinkle a little more seed-starting mix on top.
Step 4: Label your trays. This is particularly important if you’ve decided to grow more than one type of plant or several varieties of the same one.
Step 5: Now gently water the trays. Watering from the bottom is best, but most important is to avoid watering with so much force that you dislodge the seeds. Think watering can, not water pitcher. You want the soil to be damp—not dripping wet or dry, but damp.
Step 6: Poke a few holes in the plastic wrap and use it to cover the plant. The plastic will lock in the moisture, speeding up the germination process.
Step 7: Put your container somewhere warm—on a heat mat if you have one or on top of your refrigerator if you don’t.
Congratulations, you’ve started your seeds! Now, comes the hard part: keeping them alive.
You’ll want to keep a close eye on your plants, so check the containers a couple of times a day. If after a day or three, you don’t see any condensation on the inside of the plastic wrap, add a little more water. Then, at the first sign of a sprout, remove the plastic wrap completely, and move the container somewhere with reliably bright light—be it the windowsill or under a grow light. If you choose the artificial option, you want to keep the light about an inch away from the top of the plant. You’ll have to raise it regularly as your plant grows taller. It’s better to be too close than not close enough. Continue to water your plant as necessary.
The Long Goodbye
You’ll want to start prepping your new plants for life outside about a week or two before you’re ready to transplant them into your garden. You do this with a process known as “hardening off.” It’s elegantly simple: Take your plant outside and leave it somewhere safe for about an hour and then bring it back inside. Each subsequent day, leave the plant out for a bit longer.
It’s more art than science, though—if it’s a particularly hot, windy or rainy day, you’ll want to limit the time outside or eliminate it altogether. The goal is to acclimate your plant to its future environment, not to overwhelm it with the elements. Then, a few days after the final frost, you transplant your plants to your garden and say your goodbyes. They grow up so fast!