COLUMNIST: ELI APPLEBY-DONALD
So now that you know which varieties to choose from the previous article, let’s start our grow-along adventure with tomatoes and see if I can convince you to be excited too. You don’t need any fancy equipment, and I’ll try to break down the options for you to join in using either an unheated greenhouse or a sunny spot in your garden.
I’m going to repeat myself a little here because I believe this is genuinely the most important piece of advice to set you up for success. Tomatoes come in a wide variety of shapes, sizes, and flavours. If you have an unheated greenhouse, you can probably grow most of them. If, however, you are going to be growing tomatoes outdoors in your garden, then the variety you choose will make a big difference. Make sure you’ve read my advice on choosing the right variety for you before you start sowing.
Regardless of growing in an unheated greenhouse or in the garden, the one thing to remember is that tomato plants are tender, meaning they need to be protected from the cold and frosts. So, we start the seeds either in a greenhouse or indoors in the warmth of the house and we keep the little seedlings warm and safe until the frosts have passed and the garden warms up.
Now those little plants grow faster than you expect, so try to hold your excitement back a little so that you don’t start sowing too early and end up with monster plants before June.
If you have access to a greenhouse then you are super lucky because even in an average unheated greenhouse, we can start seeds off a little earlier and keep growing plants a little later. This means the range of varieties you can grow is larger. The process of sowing seeds and growing plants is almost the same, but you have the option to start in mid to late February through March.
You don’t need any fancy soil to start off seeds: you can sow them into pre-bought mixes, your own potting mix recipe, or just finely sieved compost. There are a few factors, however, to make sure your seed sowing is a success.
Tomato seeds need the compost to be warm and moist in order for them to germinate. If you can maintain a consistent compost temperature of around 18-20°C, you should see seeds germinate in 7-14 days. This temperature consistency is the most difficult part if you sow seeds in late February or even early March, but don’t despair, a little fluctuation in the temperatures will just mean your seeds will take a little longer to germinate.
One way to get around this is to use a heat mat. You can set seed trays and pots on top of the heat mat which will warm the compost from the bottom, help to maintain that temperature, and in return speed up germination.
Another factor to consider with temperatures is that once seeds germinate and you have little seedlings and plants, you need to provide protection from the colder days and, especially, colder nights. It doesn't have to be complicated though, you could cover the plants with some garden fleece at night, a propagator lid, or even cut the bottom off an old fizzy drinks bottle and use that to cover the little plant as a make-shift propagator lid.
Another point to note is that tomato seeds don’t need any light to germinate; they will, however, need light once those little seedlings pop through the soil so move them to a sunny spot in the greenhouse once the little plants emerge.
Sowing and germinating tomato seeds indoors is much the same as you would in an unheated greenhouse but with the added benefit of stable warm temperatures. A spot near a radiator or even on top of the fridge provides a nice warm spot to heat the compost and encourage germination.
Once seeds sprout and the little seedlings appear, move the seed tray or pots to a sunny windowsill to allow those little seedlings to soak up the sun, but be careful of the potential chill of cold glass. Although the windowsill can be warm from sunlight and indoor temperatures, the glass itself can be very cold so try to keep the seedlings back from it.
One thing to think about if you are planning on moving plants out to grow in the garden eventually is to not start seeds too early. Tomatoes grow quite quickly and before you know it, you have large plants desperate to be planted up, but it’ll still be too cold in your garden. My advice is to wait until mid-March at the earliest. I’ve sown tomato seeds intended for the garden in mid-April and found that to be the sweet spot.
Whether you have tomatoes in an unheated greenhouse or on a windowsill at home, there are a few general pieces of advice applicable.
Although we want the compost you sow seeds in to be moist and we want to keep it moist to help the seeds germinate, avoid too much watering of either seeds or seedlings. Seedlings need a lot less water than you may think, and over-watering can cause a tonne of issues like fungus gnats, damping off, and even fungus.
It’s always best to start off with as small a container as possible or multi-sow seeds into a seed tray. As I mentioned, seedlings won’t be happy in soggy compost and the larger the container the more compost it holds, so the more you are likely to water and the slower the compost will be to dry out. That’s where the potential risks of over-watering can become apparent.
Once a seedling starts to develop its true leaves (if you aren’t sure what these are, we have an article HERE that can help), it’s time to pot them on. Be gentle as you prize the little plants out of their first home to move them into another that’s slightly bigger. Plant them a little deeper than before to encourage strong growth.
You’ll most likely have to pot on a few times before your plants are ready for their final home. Each time you do, move the plant up to a pot that’s just bigger than the previous one.
Light is also an important factor in the little seedling’s development. Tomato plants need a lot of light, so for those of you growing indoors, you will see that the plants will lean towards the window. This is because there is only light from one direction and the plant naturally stretches out to reach it.
If you don’t want to add grow lights to help prevent this, you could try surrounding your plants on the other three sides with a wall made of tin foil. This will act as a reflector to re-direct the sunlight from the window all around the seedlings.
By June, it should be warm enough to move your indoor-grown tomatoes out to a sunny spot in your garden, and for your greenhouse-grown plants to be planted in their final home, but I’ll be back before then in each issue with more tips to help you grow-a-long on this fantastic tomato adventure.
Eli Appleby-Donald, one half of 'In the Garden With Eli and Kate' tends an productive urban garden in East Lothian. She considers herself a perpetual learner gardener, and has spent the last 11 years learning by experience, success, and failure.
Eli is a University digital educator by day, and due to the lack of good information about growing in Scotland when she started gardening, she put those skills to action and now regularly vlogs about gardening on YouTube where she has hundreds of videos about her gardening journey and her top tips, as well as appearing as a guest on other channels worldwide.
You can find out more on the fun of creating your own suburban garden paradise on either her YouTube channel, website, instagram., or her chat on the Scotland Grows Show.