Starting seeds outdoors

Judith Adam

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Pansies are cool-season plants, they like cooler temperatures, and so do their seeds.(Photo by Joanne Young)

Tips and techniques for sowing annual flower and vegetable seeds in the garden

Growing new plants from seed is one of the most gratifying experiences a gardener can have. It’s also an economical way to fill your garden with beautiful flowers and nutritious vegetables. The expert advice in this Garden Know How will help you get your annual seeds off to a strong start, regardless of what you decide to grow. – Beckie

Many annual flower and vegetable seeds are easy to sow directly in the garden, while others may need an early start indoors. There are basic protocols for soil, light and moisture, with specific requirements applying to individual plant species, and the seed packet is your best friend in this endeavour. Always carefully read the back of the packet because that’s where the most precise information is given for germinating and growing each plant. You’ll then know whether your seeds can be sown outdoors or need to be started early indoors.

Outdoor beds can be prepared in autumn for planting the following spring. Soil texture (referred to as soil tilth) is an important factor in giving seedlings a good start; they’ll be quick to put down strong roots into soil that’s friable and amended with generous amounts of organic material (such as shredded leaves and peat moss), but will struggle in compacted clay soil. Enrich the soil with moderate amounts of garden compost and composted manure to benefit plant development.

Planting seeds directly into the garden is easier than starting them indoors. Coolseason plants like radishes and peas can be sown into a furrow of prepared garden soil, covered with soil and lightly tamped down. Keep the seeds moist with daily watering until germination occurs and seedlings are well established. Choose a gentle sprinkler nozzle setting so the seeds aren’t dislodged by a strong spray.

Apply a balanced, water-soluble fertilizer diluted to half-strength after seedlings have their second set of true leaves. Diluting the fertilizer strength more than what’s recommended prevents excessive amounts of nutrient salts from accumulating in the soil and burning plant roots.

Thinning and weeding

Seeds planted outdoors usually need thinning, and there will also be weeds to contend with, too. Seedling weeds grow more rapidly than seedling flowers and vegetables, and they must be removed to prevent shading and crowding the desired plants.

Animals such as cats, squirrels and birds may also displace small seedlings. If you have a bale of straw, distribute it thinly over seeds to gently mulch and protect them from wind, and help them stay in place.

A gauze row covering purchased from a garden centre or seed catalogue can keep curious critters out and still allow light in. Remove the cover for daily watering, then place it back over the seedlings, holding the edges in place with rocks or long boards. Take off the covering when seedlings are about three inches (8 cm) tall; continue with daily irrigating and monitor for weeds.


Small seeds like those of carrots and onions, which put up a delicate little first blade, often find it hard to break through a crust of hardened garden soil. To avoid this problem, make a generous furrow in the bed and fill it with soilless mix. Sow into the soft furrow and keep the seeds moist. They’ll have a much easier time poking through the soilless mix.

Storing seeds

Seeds that are to be kept for a year or longer require careful storage. Exposure to moisture, heat and light degrade their viability. Keep seed packets in a sealed container (a plastic food storage bin works well) in a dry, dark, cool place, but don’t freeze them.

A simple homemade desiccant placed in the container ensures dryness. Lay three sheets of facial tissue together and put two tablespoons (30 mL) of powdered milk in the centre. Gather up the sides to make a little packet, seal it with tape or a rubber band, and put it in with the seeds.

Testing for germination viability

Old or improperly stored seeds may appear normal, but their viability might be seriously compromised by exposure to moisture, heat and light. To avoid disappointment, check viability before planting.

Place two thicknesses of paper towels on a sheet of waxed paper. Mist the paper towels with water until they’re wet but not dripping. Put 10 seeds spaced out on one half of the paper towels, and fold the other half over them, enclosing the seeds in the layers of moist towels, with the waxed paper on the outside. Set the packet of seeds into a plastic bag with the top folded over but not sealed to allow some air circulation. Place the bag flat on a plate in a warm place.

After five to seven days, check the seeds for germination. Look for an extending white root or any kind of green tissue. If seven or eight have germinated, there’s 70 or 80 per cent viability in the seeds. If only five have germinated, then the germination rate is 50 per cent, and it would be better to purchase new seeds

What are cool- and warm-season seeds?

Cool-season plants are flowers, herbs and vegetables that grow best in spring, before summer heat settles in. Plants such as pansies and violas, chervil, spinach, broad beans and peas all like cooler temperatures, and so do their seeds.

Pansies are cool-season plants, they like cooler temperatures, and so do their seeds.(Photo by Joanne Young)
Pansies are cool-season plants. They like cooler temperatures and so do their seeds.(Photo by Joanne Young)

Cool-season seeds won’t rot in cold soil and are capable of germinating early in the growing season. They can be directseeded into garden beds or outdoor containers, and their small seedlings will withstand cold (but not freezing) nightly temperatures.

The seeds of warm-season plants such as corn, beans and nasturtiums are susceptible to soil pathogens and likely to rot at low temperatures. Their seed packets may give the soil temperature necessary before planting them directly into garden beds.

Plant nurseries and seed-catalogue companies sell soil thermometers for measuring soil temperature. A general rule is that warm-season seeds can be planted into garden soil the first week of June.

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