Indoor sowing

Indoor sowing: a cultivation practice consisting of sowing seeds in a space where temperature, humidity, and light are controlled.

Indoor multi-seeding

Of all the techniques, I find multi-cell sowing to be the most tried and tested, and also the most effective. These trays are plastic containers divided into cells. Each cell can vary in size depending on plant needs. Space, nutrients, and the length of time seedlings stay inside all influence cell size. Multicell trays are named by their number of cells. The higher the number, the smaller the soil volume in each cell (200, 128, 72, 50, 36, etc.). You can find these trays at any nursery, as well as ordering them from agricultural suppliers’ websites.

N.B. Square multicell trays are generally preferred. Round cells tend to encourage root spiraling, which is not desired.

Potting soil

When planting indoor seedlings, it is important to know each plant’s nutrient needs. This helps you choose the right potting soil for successful germination. If a plant is demanding, then its potting soil should be a little richer. For urban vegetable gardeners, buying commercial seedling soil is often the easiest option. Organic mixes are generally preferred. If you feel adventurous, you can also make your own potting soil. This is useful when supplies run out or when you want more control. Homemade mixes let you adjust ingredient proportions. With trial and error, you can refine your recipe over time.
This helps you create a mix that suits your plants perfectly.

For the curious, here are the proportions of 2 potting soil recipes from my INAB days. They work perfectly.

Potting soil for non-demanding plants (1-3-2-1)
1 part compost
3 parts peat moss
2 parts vermiculite
1 part black earth

Potting soil for demanding plants (2-3-2-1)
2 parts compost
3 parts peat moss
2 parts vermiculite
1 part black earth

Once mixed, it’s important to moisten the potting soil until, when you squeeze a handful in your hand, you can barely see a drop of water fall. It must be stored in airtight containers to prevent it from drying out, deteriorating or becoming contaminated.

How to sow

Nothing could be simpler. Take a multicell tray or any container with holes in the bottom to let water drain. Place it in a second tray with a watertight bottom. Fill it with potting soil, then tap it twice on a flat surface to help the soil settle. Add more soil to fill the gaps, and you’re ready to sow.

Follow the instructions on the seed packet, or refer to the Tisanji app if you use it for your vegetable gardening. Most seeds should be sown at a depth equal to three times their thickness. Some seeds, however, must stay on the surface because they need light to germinate. Lettuce and celery are good examples.

When to sow?

Time spent in multicells

To determine the indoor sowing date for each species, we need to know some of their characteristics as well as a few external parameters. First of all, each plant has a different germination time: this is the time between the seed being placed in the ground and the first green shoot emerging from it. Then there’s the speed of growth. Some plants, like cucumbers, grow very quickly, while others, like peppers, take longer. That’s why they’re not sown at the same time.

The risk of frost

In addition, depending on the region you live in, you need to take into account the dates of the last risk of frost. These dates vary according to a region’s hardiness index, but also to the micro-climates it may have. In Quebec, there’s a 4-week difference between Montreal and Chicoutimi (so Montreal can start sowing indoors a month earlier!) Lastly, if you want to have certain vegetables throughout the season, you can sow them consecutively, i.e. indoors at regular intervals, so that harvesting and transplanting are coordinated and you never run out.

How to get organized?

This is where the Tisanji app comes to the rescue! Indeed, there are many ways of organizing ourselves and planning our production and task schedules, for example, with Excel spreadsheets. But this requires a lot of patience and hard work… and I’m talking about experience here! So here’s what this application does for you: you define the species you want to sow and the date of the last risk of frost in your region, and that’s it! Tisanji will organize all your indoor sowing tasks in your task calendar, so you won’t forget a thing.

For those of you living in Quebec, here’s a map showing the end of frost 8 times out of 10: last frost map

Irrigation

This is an essential parameter for successful indoor sowing. It’s important to water trays evenly to ensure that seeds receive the same conditions. This avoids creating imbalances in germination and growth. So, once you’ve sown your seeds, you need to irrigate, either with a watering can or a hose with a sprinkler head. I don’t recommend watering with a tap or hose without a sprinkler head, as the power of the spray may displace the soil and seeds.

Ergonomics

• Instead, I suggest putting your trays on a table or on the floor and practicing watering beforehand. Find a speed that you can keep constant by making large movements from one end of the surface occupied by the trays to the other. Make sure you go over the sides so that the ends of the trays also receive the same amount of water.
• For seeds that need to be deposited on the surface only, I recommend using a spray bottle to prevent them from moving around too much.
• Finally, don’t forget to group your trays by cell size. The larger the cells, the more water they require.

As for the quantity of water, this varies according to the stage of the seedlings.

Irrigation step by step

• When you’ve just put the seeds in the ground, water abundantly. You should feel a good weight difference when you lift your irrigated tray again. It’s important, however, to let the trays drain well so that there’s no accumulation of water at the bottom. We don’t want to drown the seeds or create conditions more conducive to the development of fungal diseases.
• Keep the soil moist until germination, but it’s not necessary to water every day. This depends on sunshine and temperature. Regularly stick a finger in the soil to get a better idea of the ambient humidity.
• Once germination has begun, you can slowly reduce the frequency of watering. It’s important not to give the seedlings too much water, so that they don’t become lazy and develop a stronger root system. This means they won’t be so unprepared during periods of intense summer drought. Another tip: if it’s a cloudy day, it’s best to water lightly or not at all.
• The best way to tell if a plant’s roots are healthy is to take the rootball out of its cell (don’t do this at the very beginning, you’ll simply uproot the plant) and see what color they are. Roots that don’t receive too much water and are stronger will be very white. If the opposite is true, they will be brown.

Germination and thinning

Once the plants have germinated, you may need to thin them out: in other words, clean them out. Some plants, like beet, will produce several plants from a single seed sown. You may also have sown several seeds per hole to ensure a better germination rate. If this is the case, wait until the seedlings have formed their cotyledons and their first true leaf before choosing which ones to pull out, so as to keep those that look the most vigorous.

Cotyledon: The first leaf to appear on the axis of a seed plant embryo; it is a nutrient reserve before the true leaves appear and enable photosynthesis.

Transplanting: The process of transplanting seedlings into a larger container so that they have sufficient space to grow.

Etiolation: A plant tends to be leggy if it lacks light. To compensate, it grows taller. As a result, the stem is abnormally long, discolored and frail. To avoid this phenomenon, simply place your trays in a sunny spot from the outset.

Transplanting

Some plants, like tomatoes, need to be transplanted, i.e. the seedlings are transplanted into a larger container so that they have sufficient space to grow. It’s an important step, and a fairly easy one, but one that requires delicacy. Seedlings are fragile, and if their roots are damaged, they are more likely to suffer stress. For best results, pinch the bottom of the cell to loosen the root ball and then manipulate the seedling by the stem. In general, you’ll know it’s the right time to transplant if, when the rootball is extracted, the roots occupy enough space to hold it in place.

Hardening off

This is a key stage if you don’t want the plants to suffer too much stress before transplanting to the garden. It lasts around one to two weeks. It consists of taking the trays outside during the day, so they can get used to the harsher conditions, and bringing them in at night for the first few days. (Please note! During the very first days, only take them out for a few hours, as the shock of the different elements: wind, sun, rain, etc. could be fatal if exposed for too long). Towards the end, they can be left outside at any time, just make sure there’s no risk of frost.