Techniques

Repotting tomato seedlings

If you start tomatoes indoors, move them into a larger pot after about a month. This encourages extra roots and helps the plants grow larger and stronger.

Tomato seedlings being moved into larger pots — *Moving tomato seedlings into larger pots*

Since 2023, we have used large MM-Airpots for repotting tomatoes and raising large summer vegetables. The plants grow just as well as they did in the larger conventional pots we used before, but need less MM-Mix and less space. Some older photographs still show ordinary pots.

About tomatoes

We start tomatoes indoors from late March to late April, using small Airpots and ready-made MM coconut seed-starting mix.

Keep the plants in a bright place and the mix moist, and they will grow quickly. By late April or early May, they will look something like this:

Young tomato seedlings two to four weeks after sowing — *Tomato seedlings two to four weeks old*

Repotting helps tomatoes grow faster and stronger

After four or five weeks, the plants become too large for the small Airpots and have used most of the nutrients in the growing medium. Without enough food, the leaves lose their deep green colour and the plants never become properly sturdy.

Move them into large Airpots filled with MM-Mix or MM coconut mix with plant food. This gives them fresh nutrients and more room to grow.

You will need:

fresh MM-Mix, or MM coconut mix with plant food
a bowl for the Airpots
water
large Airpots

If you do not have large Airpots, ordinary pots will work too. They must be at least 18 cm deep and have a drainage hole in the bottom.

MM-Mix Airpots and supplies for repotting tomatoes — *What you need to repot tomato seedlings*

Preparing and repotting

Stand the small Airpot containing your tomato plant in a bowl of water for a moment. A moist root ball is easier to remove from the pot than a dry one.

Place the plant at the bottom of the larger Airpot:

Tomato seedling placed deep inside a large Airpot — *Place the plant at the bottom of the large Airpot*

Fill the pot right to the top with mix.

Part of the stem and the lowest leaves are now below the surface. Most plants cannot cope with that, but tomatoes form new roots along their buried stems. These extra roots help the plant grow larger and stronger.

Stand the pot in a bowl of water so the mix can slowly absorb it.

Large Airpot absorbing water from a bowl — *The mix absorbs water from the bowl*

Put the pots back in a bright place. If the tomato plants become top-heavy and fall over as they grow, support them with a small cane.

Repotting into an MM-mini

You can also move a tomato plant into an MM-mini. This is ideal if you have a greenhouse or conservatory. The grow bag is not watertight, so it is less suitable for a windowsill.

Plant the tomato as deeply as possible here too. It will form extra roots along its stem and grow better than it would in an ordinary pot.

This is because the sides of an MM-mini let air through. As soon as roots approach the fabric, the plant responds by making new roots.

Tomato plant being repotted into an MM-mini grow bag — *Repotting tomatoes into an MM-mini (photo: SonjaMM)*

View the MM-mini

Watch the temperature, even in a greenhouse

By now, the plants take up quite a lot of room. During the first half of May, however, it is often still far too cold to put them outside.

If you have an unheated greenhouse, you can move the plants there. Keep an eye on the weather and bring them indoors overnight when very cold nights are forecast.

Tomato seedlings and other young plants in an unheated greenhouse — *Indoor-raised tomato plants in an unheated greenhouse*

Tomatoes need at least 18°C to grow well and stop growing below 15°C.

If the temperature falls well below 10°C, they may even die.

That is why tomatoes should not go into your raised bed until late May. The same applies to other summer vegetables such as courgettes, cucumbers and pumpkins. First, however, they need to get used to outdoor conditions. This is called hardening off.

Is starting seeds indoors a lot of trouble?

Quite a bit, but delicious home-grown tomatoes are worth it.

Recently repotted tomato plants on a windowsill — *My freshly repotted tomato plants on the windowsill*

Maar juist omdat je tomatenplanten dus al snel een maand of twee binnenshuis moet verzorgen, beginnen wij daar het liefst zo laat mogelijk mee: tegen half maart.

Komkommers, courgettes en pompoenen zijn iets makkelijker. Die zaai je pas begin mei binnen voor en hoeven maar een paar weekjes binnen te staan vóór ze naar buiten mogen. Dat is beter te doen.

En als je dan tóch al die moeite doet: kies dan in ieder geval voor de beste én de lekkerste soorten.

Mijn favorieten vind je hier:

Go to the seed shop

Good luck!