COLUMNIST: ELI APPLEBY-DONALD
But before you rush out to plant tomato seeds in your back garden, there are a few things you should know to set yourself up for success.
Let’s start by addressing the elephant in the room: greenhouses. If you’ve been growing in Scotland for any length of time, you have likely heard that greenhouses are the way to go for tomatoes, and for good reason!
Greenhouses offer protection from the elements, providing a stable, warmer environment which tomatoes love. Generations of Scottish gardeners have relied on them, and they’re still a proven method for growing a bountiful crop and extending the growing season.
While our neighbours down south have a slightly easier time due to warmer, more consistent weather, outdoor growing can be done here too. I’ve tested it myself, trying different varieties in three outdoor spaces: a raised bed, large pots, and a vertical planter. The results? Positive!
I want to rephrase our question to: is there a trick to getting bumper tomato harvests outdoors in Scotland?
Let’s not pretend that Scotland’s weather is ideal for tomatoes. They are a plant that naturally hails from warm places like South America, so our cool, rainy climate presents a challenge. But don’t lose heart, with careful planning of the varieties you grow, you can still manage to coax a decent harvest from your plants, and it’s not necessary to only grow cherry tomatoes either.
The biggest hurdle is the consistency of our weather. Tomatoes need warm temperatures to set fruit, grow, and ripen. Ideally, we’re looking for nights consistently well above 10°C and days that are warmer. The season for growing tomatoes is all about the temperatures being in the sweet spot region.
The main stages for tomato growing are germinating the seeds, growing seedlings, planting out or into their final homes, setting fruit, and then ripening that fruit. We want all of this to be happening before our weather gets too cold and dark. The number of days you have in your growing space (garden or greenhouse) that can meet the plants' needs is your growing season for tomatoes and you will find there is a bit of variety in this around Scotland.
So how would you work this out? Well quite simply you need to count the number of days where you know the temperatures will be warm enough for your little tomato plants to survive, so ideally above 10°C at night and warmer still during the day. This is your tomato growing season.
This is where it’s worth noting why greenhouses are useful. As you can imagine, you will be able to provide a consistent 14°C or 15°C temperature in a greenhouse long before you can guarantee that outdoors and again, towards the end of the season, your greenhouse will hold those warm temperatures for a little while longer so they do extend the growing season.
When we talk about growing tomatoes outdoors here in Scotland, we are never talking about sowing the seeds outdoors. We will always be sowing seeds in a greenhouse or indoors on a sunny windowsill. We are counting how many days we have for our season and thinking of that as the time that little plant will be growing, the time as a seedling is pre-season.
I find that I can sow my tomato seeds in my unheated greenhouse in March and only need to provide a little bit of protection to the seedlings on the coldest nights, usually just a cloche cover of some kind (a plastic fizzy drink bottle, propagator lid, or garden fleece) and I can keep my tomato plants in the greenhouse until it’s warm enough for them to be transplanted out into the garden, or if you are growing on in the greenhouse, into their final container or bed. This is what I count as the start of my season when I can set my plants out in their forever home.
If you followed my pepper grow-a-long last year this will be similar in that I’ll be giving advice in each issue throughout the year based on my growing experience of tomatoes. This your very first piece of homework: your season.
I want you to go grab a pen and paper and any weather data you can get your hands on for your garden and note when your temperatures at night are usually, consistently, above 10°C. For me that’s usually the start of June.
Next, I want you to do the same thing for the other end of the year, when do you no longer have those warm nights with the very minimum temperature of 10°C? That is the end of your tomato growing season. If you plan to grow in a greenhouse then factor these temperatures for your greenhouse, so your season might be early June to late September or even early October, depending on where you are growing.
Once you have your start and end point, count how many days that is. This count of days is your perfect tomato growing season, and we are going to use this to match tomato varieties to your garden or greenhouse to give you the best chance at a bumper crop.
Here’s where things get interesting. The success of your outdoor tomato-growing efforts will depend a lot on the varieties you choose. Not all tomatoes are going to love our climate, so it is essential to pick those with shorter growing seasons.
Think about varieties like cherry tomatoes ‘Sun Gold’ and ‘Sweet Million’. These are excellent choices, not because they are cherry tomatoes but because their growing seasons are a relatively short 60-65 days. This means they will grow to maturity, or rather they will begin to form fruit and begin to ripen quickly, making them better suited to Scotland’s shorter growing season.
In my own garden, I grow a mix of determinate (bush tomatoes) and indeterminate (vining tomatoes), a mix of full-size plants and dwarf plants. Bush tomatoes tend to produce their fruit in a shorter time and almost all at once, which is a bonus if you’re battling the clock. I also experiment with dwarf or micro varieties. These are particularly good for our conditions because they can have growing seasons as short as 40-50 days, perfect for squeezing in a quick crop before the weather turns but usually also produce large harvests. These are without a doubt the most successful tomatoes outdoors in my garden.
While growing tomatoes outdoors is absolutely doable, having a greenhouse gives you a big advantage. For one, as I mentioned, it extends your growing season. A greenhouse traps warmth and protects plants from the chill, allowing you to get started earlier in the year and keep things going for longer. This opens up the number of varieties you can grow.
If you’re keen to grow larger tomatoes, like beefsteak or multiflora cherry varieties like ‘Barry’s Crazy Cherry’ or ‘Lufichoise,’ a greenhouse might be your best bet. These types need a bit more time to ripen and are less likely to do well outdoors in Scotland’s shorter summer. The added warmth of a greenhouse can be the difference between green tomatoes and a fully ripened, juicy harvest.
Firstly, I always recommend you speak to experienced tomato growers in your area. They will have recommendations and knowledge of what works in your area. If you want to do a bit of investigating however, you can search online for something called days to maturity. This is essentially the season for that specific variety, how many days it will take from planting up until you are harvesting fruit.
There is a list of some of the tomato varieties that I have grown on the next page which have less than 100 days of maturity. I’ve marked the ones I’ve successfully grown outdoors in my garden. The key is to pick varieties that match your growing season.
In the end, if you’re up for the challenge, outdoor tomato growing in Scotland can be a hugely rewarding experience. So why not give it a go this season? There’s nothing quite like enjoying a tomato you’ve grown yourself, and even moreso knowing that it has thrived in our beautifully unpredictable Scottish climate. Or, use this new knowledge to try a new, fancy variety in the greenhouse.
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.