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Sprintime Fun! Your Guide to Starting Strong Seedlings


Our guest blogger this month is Sarah Lawrance. After many years of backyard gardening and working on organic farms in southern Ontario and western Quebec, Sarah spent four years growing an assortment of certified organic herbs & vegetables as part of the Just Food Start-up Farm. Sarah’s organic seedlings have also been a perennial favourite at the Ravenswing Arts & Music Fair in Centretown. Sarah now works at the Ottawa Public Library and is still committed to making organic food accessible by providing growing information to help you produce strong, healthy plants. 

A big part of growing a great garden is to start with strong, healthy seedlings. I’m excited to share some of the organic growing tricks I’ve learned over the last several years! 


Seeding tomatoes and peppers

If you’re gardening in Ottawa, start peppers in early April and transplant to the garden in early June. Tomatoes need less time to reach transplanting size and are more cold-hardy, so start these in mid-April and transplant in late May.

To begin, pour some soil mix into your seed-starting container. I like to use something called a 48-cell insert, which fits into your typical 11”x21” plastic greenhouse tray and can hold 48 plants at a time. For home use, you can use rinsed yogurt cups or something similar, with holes poked into the bottom for drainage. I don’t recommend using anything smaller than 2.25”x1.5”x 2” deep because your plant roots need room to grow!

Lightly pack the mix into your container and add some more. You don’t want it so densely packed that the roots can’t breathe, but you also don’t want the soil too fluffy. Once containers are filled use your index finger to poke a hole in the soil, about 1” deep.

Plant 2-3 seeds per container; it’s normal for some seeds to not germinate. New seeds will have a higher germination rate than old seeds, so you can use more or less seed based on that.

Once your seeds are sown, loosely cover with more mix and lightly pat down to ensure contact between the seed and the moist soil. At this stage I usually bottom-water my containers so as not to disturb the seeds; do this by dipping the bottom of the container into a tub of water so it can be absorbed from below. Do as needed until the seedlings become established; a heavy container usually means it still holds a lot of water and doesn’t need more; a light container often means it needs watering.


Caring for your seedlings

After you’ve seeded your plants, there are a few more things I recommend.

1) Light: Some gardeners grow seedlings in a sunny window. I’ve never had much luck with this because they lack enough direct sunlight; they seedlings tretch and get “leggy”, which weakens them. I use a standard fluorescent light fixture from the hardware store and use bulbs rated “sunlight” or “daylight”. You do NOT need expensive, full-spectrum lights for starting seedlings! Start with your lights close to the tray—the closer they are the less your seedlings will want to stretch, and less stretching means stronger plants. Do this by hanging your lights with an adjustable chain or by propping up your trays from below. As they grow you’ll want to raise the lights (or lower the tray) so that the tops of your plants are always 1-2” from the lights.

2) Water: Bottom-water for the first few weeks, then use a water bottle or small watering can with a narrow tip to water the soil (rather than the leaves). You will want to make sure the soil doesn’t dry out, because plant roots need moisture to absorb soil nutrients. Proper drainage is also important as soil that’s too wet can develop a fungal condition called “damping-off”, which rots the plant from the bottom-up.

3) Thinning: Since you’ve planted 2-3 seeds per container, you might get more than one seedling in each. Thinning means selecting the strongest seedlings and removing the others. Once the seedlings have developed 1 or 2 sets of “true” leaves (the leaves that come after the first two “seed leaves”, which have a different shape), it should be clear that one plant in each container is stronger than the others. I recommend snipping the weaker/smaller ones at the base of the plant rather than pulling them out, as pulling can damage the roots of the remaining healthy one. I never recommend leaving more than one seedling per container for this type of plant because they will compete for space, water, and nutrients; this will ultimately weaken both.

4) Hardening off: This means getting your seedlings ready for transplant! The point of hardening off is to let your new plant slowly adjust to the harsher conditions of being outdoors: direct sunlight, hot and dry days, cool or cold nights, and windy conditions. I usually start this 2 weeks before transplant. Pick a mild day and put your plants outside in a spot that’s relatively sheltered from sun and wind for a few hours. Do this for a couple of hours at first, increasing the exposed period by a few hours each time and giving them increasingly more exposure to the elements until they are able to spend the entire day and night outside. At this point they will dry out a bit; this is expected because they must get used to the reality of their new environment. Be sure to water them after the sun goes down or before the sun comes up so the water doesn’t evaporate right away. 


Seed-starting soil mix

A few years ago I developed an organic mix that produced startlingly healthy seedlings. The mix was originally based on Elliot Coleman’s recipe for soil-blocks, but I’ve tweaked it to suit more typical seed-starting styles:

25 cups “Organik” Pro-mix (contains: peat moss, coir, perlite, limestone, and mycorrhizae)

20 cups compost (my favourite brand is “Meeker’s Magic Mix” fish compost from Manitoulin Island)

1/4 cup bloodmeal

2 Tblsp bonemeal

2 Tblsp greensand

2 Tblsp kelp meal

Each ingredient in this mix plays an important role in balancing nutrients and ensuring the soil has the right balance of water-retention and breathability. With this mix I have been able to grow happy, healthy tomato seedlings in small containers until they reach transplant size.

I recommend combining all ingredients in a medium-to-large storage container and then slowly mixing-in a few litres of water. If the mix is really dry the water will take longer to incorporate properly, so at first it might end up looking much wetter than it really is. Since an evenly moistened soil is important for seed germination and root development, I start with 2-3 litres of water, mix it in thoroughly, and then let it sit for a day or overnight. It usually needs more water when I return.

People often worry about their soil being too wet: Take a handful of your moistened mix and squeeze it. The ideal moisture level will cause the mix to stay clumped together when you open your hand, but without any excess moisture seeping from between your fingers when squeezing it. If it doesn’t stay clumped, add water. If it’s too wet, incorporate more Pro-mix and let it sit for a bit longer.

When you’ve achieved this, you’re ready to start seeding!

Sarah Lawrance