How to - Seeds

Eight seed-starting basics

Get a jump-start on the growing season with these easy tips


You might think growing from seed is a practice only for advanced gardeners, but it isn’t difficult to get the basics down. Rule number one: Don’t sow too early or your plants will be leggy and overgrown long before you can transplant them into the garden.

In my experience, if the seed packet recommends sowing four to six weeks before the last frost date, it’s better to pick the four- rather than the six-week date. (To calculate the sowing date, count back from your region’s last frost date; for me in southern Ontario, that’s the third week of May.)

1. Choosing seeds
Annuals and vegetables are the easiest to grow. Perennials, however, are trickier because most need a period of cold to break dormancy and take a couple of seasons to reach flowering size.

2. Containers
Propagating kits (available at garden centres or hardware stores) include four or six cell packs, a tray to hold the packs and a plastic lid. If reusing containers, wash with soap, water and a little bleach, and make sure they have drainage holes. Newly sprouted seedlings may look alike, so label containers as you sow.

3. Sowing medium
Use fresh, sterile seed-starting mixture (available from garden centres). Moisten mixture about an hour before sowing; it shouldn’t be soggy, just as damp as a wrung-out sponge.

4. Follow directions
Seed packets contain information on timing, lighting requirements, sowing depth, and optimal germination and growing temperatures.

5. Keep moisture in
Lightly water freshly sown flats, then cover with plastic dome lid, or if reusing containers, place them inside a plastic zip-lock bag. At the first signs of germination, uncover or remove from plastic bag.

6. Watering
When the top of the soil looks dry, water carefully using a small watering can with a fine spray. Avoid overwatering: soggy soil and poor air circulation can lead to damping off, a fungal disease that can kill baby plants. Prevention is best, but the fungicide No Damp can also help.

7. Light
A bright window works, but grow lights or cool fluorescent tubes are better. Keep seedlings about eight to 10 centimetres from light source to prevent plants from becoming too spindly. Plug lights into an automatic timer set for 16 hours on, eight hours off.

8. Fertilizer
When seedlings have two sets of true leaves (the first leaves are called cotyledons—or seed leaves—so wait for the true ones), start feeding once a week with a balanced (20-20-20), water-soluble fertilizer at half-strength, working up to full strength after a few weeks.

Take it outside
Plants grown indoors need hardening off before they are planted outdoors. After the last frost date, start by setting them outside in a shady, sheltered spot, initially for half a day, then gradually leaving them out all day. Progressively move them into sunnier and windier areas to acclimatize to garden conditions.

Cool-season annuals such as pansies and snapdragons can be hardened off several weeks earlier than tender, heat-loving ones such as impatiens and tomatoes.


Photo: Heike Kampe/istock

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