Tending to your own veggie garden is a fun and budget-friendly way to get some fresh produce on the table come summer. To benefit from a longer growing season and increase your chances of a healthier crop, consider starting your seeds indoors this spring. Here, a step-by-step guide to thriving seedlings.
1. Consider your space
“Pay attention to how much light you’re getting throughout the day as that will determine what type of seeds you can grow,” says Ohemaa Boateng, the program manager at Green Thumbs, a food growing education organization in Toronto. For beginners, she recommends starting with no more than three varieties of seeds. To narrow it down, consider what you like to eat, or opt for plants that are easy to grow, like tomatoes, beans and leafy greens. Buy your seeds from a local supplier, as they likely carry varieties better suited to the growing conditions in your area. Timing varies based on what you’re growing and where you live, but late February to early March is a good time to start thinking about planting seedlings in most parts of Canada.
2. Sow your seeds
Poke holes in the bottoms of your pots to ensure proper drainage, then fill them with a seed-starting mix: a fine, soilless mixture of coco coir, perlite and vermiculite that allows seedlings to grow roots easily. A good guideline is to plant seeds at a depth equal to three times their width (consult the packaging, as instructions can vary, and some tougher seeds may need to be soaked overnight prior to sowing). Boateng suggests planting a few seeds per pot in case one doesn’t sprout.
3. Label them as you go
Keep track of your soon-to-sprout seedlings by labelling them right away with the name of the plant and the sowing date.
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4. Get the temperature right
Some seeds need warmth to germinate, while others, like leafy greens, fare better in cooler soil. Keep fruiting plants—like tomatoes, peppers and eggplants—somewhere warm, such as on top of the refrigerator or near a radiator. To help retain heat and moisture, cover the pots with plastic wrap; remove once any shoots start poking through.
5. Manage water levels
The seed-starting mix should be moist but not saturated. To ensure your seedlings are watered properly, Boateng suggests setting up a self-watering system by placing one end of a string into an elevated water-filled container and the other in the soil. The water will travel down the string and nourish the plant’s roots.
6. Move seedlings into the sun
Once seedlings sprout, move your plants to a cool, sunny location, such as an indoor windowsill. Rotate the containers every so often to keep seedlings growing evenly. (Some herbs and leafy greens will grow better in shadier areas out of direct sunlight.) The temperatures needed depend on the type of vegetables you’re growing, but Boateng says room temperature works for most plants at this stage.
7. Fertilize your plants
Once seedlings grow their true leaves—not the first leaves to sprout, but the next round—it’s time to fertilize. Boateng says organic and natural fertilizers will give your plants the best nutrients.
8. Thin your seedlings
To ensure your plants have room to grow, keep just one seedling per pot. Save the healthiest, strongest-looking seedling of the bunch and snip the others off at the soil line with scissors.
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9. Harden them off
Outside, pampered seedlings can be exposed to fluctuating temperatures, rain and wind, which can cause stress and lead to stunted growth or death. To prevent transplant shock, slowly acclimate your plants to the elements (a process called “hardening off”) by bringing them outside once daytime temperatures start hovering around 10 degrees Celsius. Start with one hour a day, Boateng says, and gradually increasing their time outdoors over the course of one to two weeks.
10. Transplant them outdoors
The best time to move seedlings to their permanent home is after the last frost in your area. Wait until the plant’s root system is strong and starts to poke through drainage holes. If possible, plant them early in the morning to avoid immediately exposing them to the sun. Boateng suggests spreading mulch around the base of the plant to help keep the soil damp.
For people with smaller outdoor spaces, like balconies, Boateng recommends veggies that grow upward, like beans, cucumbers or tomatoes. “It’s maximizing the space you have by growing up instead of growing out,” she says, noting that you can use any sort of vertical support, such as a fence, cage, stake or trellis.
No seedling pots? Reuse these household items instead.
Toilet paper rolls
Make a few slits around one end of each roll and fold the sections in toward the centre to form the bottom of the pot. Planted along with the seedlings, the cardboard will decompose in the soil.
Cut bottles in half, poking drainage holes in the bottoms. Or use up the top halves by poking holes in the cap and filling the bodies with seed-starting mix, and then setting them inside the bottom halves to collect excess water.
An inexpensive and all-natural option, eggshells make excellent seedling pots. When crushed, they break down and enrich the soil with calcium, providing extra nutrients to the growing plants.
Cardboard egg cartons are compostable, so they’re perfect for seedlings. Poke holes in the bottom of each compartment and cut the lid off the carton to use as a drainage tray.
Give plastic tubs and containers—like yogurt cups—a new purpose by rinsing them out and adding drainage holes. When seedlings are ready to be transplanted, wash and recycle (or reuse) the pots.
This article was originally published in 2021; updated in 2023.