Growing tomato seedlings at home:

Sowing your own tomatoes saves you money, but above all it gives you a CHOICE in the immense biological heritage that exists! With almost 40,000 varieties to choose from, it would be a shame to grow the same tomatoes as those found in supermarkets.
For successful tomato sowing, it’s essential to take a number of factors into account. First of all, it all depends on the conditions of your sowing area, the amount of sunshine in your region, the number of sowings and the choice of varieties. There are many varieties of tomato, from traditional to cherry, early to late, dwarf to micro-dwarf. But basically, the principle remains the same.

Sowing seeds: an investment rather than an expense

Before starting your seedlings, prepare your equipment. You’ll need pots, cups, terrines or honeycomb trays, potting soil or specific seedling substrate, tomato seeds and a seedling tray. You can also opt for a mini-greenhouse or chassis to maintain constant humidity, but this is clearly optional (we do just fine without, in our context). Make sure that all your utensils and surfaces are clean to prevent the spread of disease.

When to sow tomatoes?

Well, it depends…
The best time to sow tomato seeds depends on your region and climate, and whether you plan to plant your tomatoes outdoors (around mid-May) or in a greenhouse (mid-April, or even earlier for those living in the south of France). In general, sowing can start between mid-March and mid-April, so that you can plant beautiful plants around mid-May.
Of course, if you plan to plant earlier in the greenhouse, sow earlier. But there’s no need to sow in January, as your plants will wear out in their little pots and may be in poor condition by the time you plant them.
NB: Tomato rootstock can be sown in January or February (but this will be the subject of a future article).

Which soil and pot to use for seedlings?

Again, it depends….

There are several strategies available to you (all equally valid, but unfortunately the Internet is not a place that promotes nuance… everyone will tend to tell you that their method is the best…).

So you can :

– Sow a seed in a pot, directly in potting soil (or a mixture of soil and compost). But avoid cold garden compost, which is generally full of seeds).
– Sow a seed in a pot, in seedbed soil (but at this point you’ll need to transplant into richer soil to avoid starving your plants).
– Sow 2 or 3 seeds in a pot (eliminate the smallest plants to leave only the most beautiful).
– Sow « loose » in a bowl (with seedbed soil) and later transplant into individual pots.
– Sow 1 seed in each hole of a honeycomb tray (and transplant into individual pots at the 3 or 4-leaf stage).
– Sow 2 seeds in each hole of a honeycomb plate (and eliminate the smallest plants to leave only the most beautiful). Personally, this is the method we use).
Here too, you can either sow in seedbed soil (draining but poor in nutrients, or directly in potting soil.
Personally, we prefer the 2nd method, which allows us to have 100% full plates).

ATTENTION: Peat moss « eco-trucbidulle » pots or egg cartons are by far the WORST possible CONTAINERS. DON’T USE THIS!!! It’s always either too dry or too wet, it doesn’t grow well, in short… Absolutely avoid!!!

Once you’ve made your choice, let’s move on to seeding:

Fill your containers (pots, trays, terrines) with potting soil or seedbed soil, packing lightly (dropping them onto a 10cm-high table is enough to pack the substrate). Make a small hole about a centimetre deep (about one phalanx) with your finger or a suitable tool. Place one or two tomato seeds in each hole, then cover with potting soil. Water gently to maintain constant humidity, without letting the water stagnate.

The first stages in the life of your tomatoes

Germination of tomato seeds takes about one to two weeks (max.), depending on temperature and humidity conditions. Make sure you maintain a constant temperature, ideally around 20°C. If it’s difficult to reach 20°C in March in your home… you can use a heating mat or heating element to place under your seedlings.
Once the first leaves, called cotyledons, are visible, you can remove the weakest ones, leaving just one plant per cup or pot. To ensure the proper development of your tomato plants, it’s important to provide them with sufficient light. If they don’t get enough light, the seedlings will stretch out in search of light. And that’s not a good sign… A healthy plant is one that is stocky with a thick stem.

Aren’t lamps perma?

If you don’t have direct exposure to the sun (like in Geneva, a region where the fog is persistent in March…), you can use horticultural lamps to stimulate growth and prevent seedlings from spinning. Don’t forget to keep them at an appropriate distance (20 to 30cm) to avoid burning young seedlings if the lamp is too close, or rendering the lamp useless if it’s too far away.
NB: a little physics reminder. The power of a light source is inversely proportional to the square of the distance: roughly speaking, if I move the lamp away by one length, the light received by the plants decreases by 2. If I move it away by 3, the intensity decreases by 9, if I move it away by 4, the intensity decreases by 16… and so on.

https://fr.wikipedia.org/wiki/Loi_en_carr%C3%A9_inverse

When it comes to choosing lamps, we advise you to avoid hard-discounters, @maz@ne and the like… go instead to retailers specializing in « indoor cultivation », who are, until proven otherwise, the specialists in the field (an article on choosing lamps is forthcoming). As for lamp wattage, unless you want to grow melons in your living room, we recommend around 30W/m2. Of course, if you have 200W it’s bound to grow better, but is that really useful?… The idea behind the lamp (for us at least) is above all to prevent the plants from « spinning ».

Cost(s) for sowing under a lamp

Regarding the cost of a lamp (obviously it depends on your KW/h rate…), for 30W, and a 2-month run, you’re looking at around 10 or 20 CHF or €.
In terms of ecological costs, I personally prefer to use 30W in Switzerland, which has relatively clean energy, rather than buying plants (generally grown in Holland, a country not really known for its mountains or dams…).
In all cases, the lamp is there to prevent your plants from spinning, so if the conditions at home mean that your plants don’t spin, DON’T USE LAMPS! If you live in the mountains (which means you’ll be planting in June), start your seedlings in mid-April, and DO NOT USE A LAMP!

Watering and transplanting tomatoes

During this growth period, keep your tomato plants well watered, but without drowning them. Use a sprayer with a fine nozzle to water at the base of the plant and avoid spraying the foliage. Watering depends on the heat in your home, humidity levels and the size of the plants, so it’s hard to say how much to water…
Personally, I always weigh the pots (or trays) when the potting soil is dry, then when it’s full of water. After a bit of practice, when you lift a pot you’ll be able to tell right away whether it contains water or not.
When the seedlings have between 3 and 4 leaves (not counting cotyledons), it’s time to transplant them into individual pots (5X5cm to 9X9 pots, beyond which they’ll take up a lot of space and cost you a lot in potting soil…). When transplanting, we advise you to choose the best possible potting soil. We use « All-Mix » potting soil from « grow shop ». These are « technical », organic potting soils, but unfortunately their carbon footprint is deplorable…. (Siberian peat moss, coconut wool from the islands, guano from elsewhere, perlite…). But these potting soils have exceptional qualities! Much better than most « professional potting soils ». Personally, I don’t recommend using them for one or two plants (the ecological impact outweighs the benefits), but for fifty plants it’s debatable… For 100 plants or more, we think the ratio is positive. But it’s up to you to decide what’s eco and what’s not. If you want to use more « natural » substrates, sifted garden soil mixed with compost will also do the trick (but it won’t grow as fast).
Once you’ve finished transplanting, all you have to do is wait a week or two, then start getting the plants used to direct sunlight and the coolness of the outdoors. And wait until planting.

Tomato planting

That’s another story….?

To find out more:

Grafting tomatoes

https://www.youtube.com/watch?v=3B4yzs3LxmI

https://www.youtube.com/watch?v=-C9J_NbLe2k

Humorous video on the « effects » of the moon

https://www.youtube.com/watch?v=GKoug-7P_Xk

Less amusing but more complete, a study by France’s national horticultural society: https://www.snhf.org/wp-content/uploads/2016/10/jardiner-avec-la-lune.pdf

Proscpecierara: Swiss Foundation for the Protection of Cultivated Heritage

https://www.prospecierara.ch/fr.html

The (magical but polluting…) soil we use

https://www.biobizz.com/fr/producto/allmix/

Calculate lamp consumption:
https://particuliers.engie.fr/electricite/conseils-electricite/conseils-tarifs-electricite/comment-calculer-consommation-electrique.html

Our tomato seeds store :

https://grainedecarotte.odoo.com/

If you would like to learn about permaculture in Geneva or the French-speaking part of Switzerland, please visit ourevent page to see our next dates and seedling workshops.