Seed Starting Primer

For the most part, seed starting is easy if seeds are given the right conditions. Seeds want to grow! Seedlings can be grown in very small space, even on your kitchen counter or a sunny window ledge. If you are able, it’s helpful to set up heat mats, a grow rack & grow lights, but these are not a necessity to get started.

In our short season Canadian Prairies (growing zone 3) many seeds need to be started indoors because the outdoor growing season just isn’t long enough to grow plants from seed to fruit. Examples of plants that always need an indoor head start are the heat-loving ones: tomatoes, peppers, and eggplant. If you wanted to grow something like the very long season globe artichoke (120 days to maturity) here in Manitoba, it would need even more time indoors! You may realize certain plants just aren’t meant to be grown here, at least not very easily.

Many other plants can benefit from an indoor head start too, for example long season cabbage, broccoli, melons, squash, and cucumbers. Slow growing herbs (e.g. lavender, thyme, echinacea) and many flowers are also usually started indoors in order to get a harvest that year. Some annuals (e.g. rosemary) can be brought back indoors over winter, then grown outdoors again the following year.

The basic requirements for starting your own garden seeds are viable seeds, starter soil, heat, light, moisture, containers, and proper timing.  Some seeds need a cold stratification period or scarification ahead of planting. You may have heard about soil blocking, which works well with local wool pellets like these from our friends at Longway Homestead. We also recommend organic all-purpose starter soil (now available as “soil in a box” to avoid plastic!), Ecotea and eco worm castings, produced locally and sold at Sage Garden Greenhouse in Winnipeg.

Let's go into a bit more detail on each seed starting requirement:

VIABLE SEEDS
It's important to know the seeds you are starting are still viable.  If seeds have been stored in cool, dry, dark conditions, they should be viable for several years.  Smaller seeds tend to have a shorter lifespan but that is not always true.  Tomato and cucumber seeds can be viable for up to 10 years!  If you are not sure, either perform a germination test ahead of planting, OR seed heavily assuming not all seeds will come up.

Here are some ideas of lifespan of garden veggie seeds (credit to FedCo Seeds for this information):

Beans 2-3 years
Beets 3-5 years
Brassicas 3-5 years
Carrots 2-3 years
Celery 2-3 years
Corn 2-3 years
Cucumbers 5-10 years
Eggplant 2-3 years
Leeks 2 years
Melons 5-10 years
Mustard 3-5 years
Onions 1 year
Parsnip 1 year
Peas 2 years
Peppers 2-3 years
Radish 3-5 years
Spinach 2-3 years
Squash & Pumpkins 2-5 years
Tomatoes 5-10 years

STARTER SOIL
Not all soil is alike.  To give small seeds a head start indoors, generally seed starting soil is used (not garden soil). Garden soil has weed seeds that will also germinate, and is also usually heavier than starter soil.  Sterilized starter soil gives your indoor seeds a clean head-start.  Starter soil can be mixed with wool pellets (slow release fertilizer), compost (e.g. worm castings), and something to lighten it (e.g. peat or coconut coir).  Many starter soils are available, a ready-made one can be purchased if you don't want to mix your own.

HEAT
Seeds need heat, light and moisture to germinate properly.  In fact, some seeds need an extended period of warmth at a consistent temperature in order to germinate (e.g. peppers, celery).  Heat mats are useful as they keep the soil warmed from below, especially helpful if your house is on the cold side.  Some people build heated sand tables, but that is something you will want to get into if you are growing on a larger scale.  Setting plants under grow lights also offers some heat to the seedlings.  Heat is important, but it can also dry out the soil faster than without added heat.  Keep an eye on watering if you are using heat mats.

LIGHT
Seeds are interesting.  Some need light to germinate, and some need darkness.  Read your seed packages carefully to determine what your seeds need, and how much soil they should be covered in when planting.  A general rule of thumb is that seeds are usually covered with about 2 x the amount of soil as the thickness of the seed.  Seeds that need light to germinate as lightly pressed onto the surface of the soil, but not covered.  After seeds have germinated, light is needed by all.  This can come in the form of grow lights, or setting plants in a sunny window.  The lights may be an expense, but they allow for uniform upright growth, whereas plants set in a window may become "leggy" as they stretch toward the light.  Trays of seedlings can be rotated so they take turns under best light conditions.

MOISTURE / AIR FLOW
Seeds and seedlings need both adequate moisture and proper air circulation.  It is important not to let seeds dry out as they are germinating, however they can also get too wet causing mold to grow.  Seed trays are often covered with plastic dome lids to create a mini "greenhouse" effect while seeds are germinating.  Keep a watch that these don't get too humid (they are called "humidity domes" for a reason).  If the domes are getting humid, remove them or allow a bit of airflow in.  Once seedlings are up, they need regular watering.  If they are set into solid trays, the plants can be under-watered which helps avoid the dreaded "damping off".  A small fan can be set near the seedlings to bring air flow into the room (be careful not to damage the fragile seedlings with too strong a fan), and seedlings can be gently brushed with your hands to stimulate growth and provide movement.  This strengthens the seedlings for when they move outdoors into the wind.

CONTAINERS
Seeds can be started in almost any type of container, as long as it has some drainage and enough room for roots to spread.  The most common are black plastic seed starter trays and nursery pots, which should be sanitized from one season to the next so they can be reused.  They can be washed, or set outside in the sun to solarize.  If you want to avoid plastic, look for ceramic containers, or start seeds in wooden boxes.  Wooden boxes work well with soil blocking too, as the boxes can be built to fit soil block sizes perfectly.  Wood is a great choice for long lasting seed trays.

PROPER TIMING
If you check your seed packages, you will notice "days to maturity".  This generally means how many days a plant takes to grow from seed to harvest.  Packages will also usually say how many weeks ahead of last frost that seeds need to be started indoors (e.g. 4-6 weeks indoors).  Depending on the growing zone, many plants need to be started indoors in order to have a long enough growing period.  Understand the last frost date for your region, then work back from that date to know how many weeks in advance you need to start your seeds.  Here in Manitoba the last frost date is commonly regarded as being around May 24, so work back from that date when you are starting seeds.  All the heat loving plants like tomatoes, peppers, eggplant, melons, cukes, squash and many herbs & flowers need to be started indoors ahead of time for best harvest results!  Sometime we start seeds like sunflowers indoors to avoid the seeds being eaten by wildlife, even though they could be grown out as a short season annual. 

Of course, before any seedlings get transplanted outdoors into the garden they need to be hardened off (i.e. prepared for the wind and sun), and it's good to get a weather report for the coming weeks to know if your tender seedlings will need any protection.  More on growing seedlings in another post.

Happy seed starting!