Growing Tomatoes in Cooler Climates

20 February 2020, written by Ann Marie Hendry

I struggled with tomato growing for a long time. While gardeners in warmer regions drowned under more tomatoes than they could eat, in my garden plants would sulk for a few months before reluctantly producing a few lacklustre red fruits by the end of August. I was losing patience.

But then things changed. I met a variety called ‘Latah’, which was touted as being suitable for cool, short summers. Initially I was sceptical of the claims, but the young plants grew with cheerful vigour and started producing flowers and fruits fast – very fast. They were flowering long before I was ready to move them from my windowsill into the greenhouse, and – miracle of miracles – I tasted the first ripe tomatoes before the end of June!

This was an important lesson: healthy soil and protection from the elements will take tomatoes so far, but in cooler climates, thoughtful variety choice is required to get them past the post.

Choosing Cool Climate Tomatoes

Even with the added warmth of a greenhouse, tomato plants need to be tough to succeed in my garden. Varieties that flourish just a couple of hundred miles south won’t necessarily have what it takes to succeed here; and reliable favourites in my garden may not be hardy or rapid-growing enough to provide a harvest further north, where temperatures are typically cooler.

So which tomato varieties will do well in cooler climates? The best way to find out is to use local seed suppliers where possible, as they are likely to offer varieties well suited to your area. Or hunt down tomato varieties that were bred in your country or state. Country of origin may be mentioned in the description in seed catalogues, or even in the variety name.

Determinate or bush tomatoes are often a safer bet too. They tend to produce fruits earlier, giving you a better chance of gleaning a ripe harvest before the first frosts.

10 Cool Climate Tomatoes to Try

Some of the varieties below I’ve grown personally, and others are on my must-grow list. All are worth a try:

Ailsa Craig: Early Scottish-raised all-rounder that sets a high flavour benchmark.
Beaverlodge: Highly productive Canadian-bred variety, recommended for containers and hanging baskets.
Glacier: Potato-leaved, very early low-growing salad type that is particularly tolerant of cooler temperatures.
Latah: Very early, flavoursome fruits which are variable in size and sometimes ribbed.
Moneymaker: A tried-and-tested salad tomato that is, as the name suggests, reliably prolific.
Red Alert: Early-fruiting cherry tomatoes, said to be very flavourful.
Shirley F1: Good disease resistance and high yields of medium-large fruits.
Siberian: Low-growing salad tomato that sets fruit at low temperatures.
Stupice: Another early potato-leaved variety, this time bred in the former Czechoslovakia.
Sub-Arctic Plenty: Very early tomato that will set fruit in cool conditions.

Ways to Grow Better Tomatoes in Cooler Climates

Even the most cold-hardy tomato varieties are heat-lovers at heart, and there’s little you can do to persuade them otherwise. Starting them off indoors is essential. Sowing seeds in a propagator is ideal, but anywhere else that provides bottom heat will do – try placing seed trays on top of your fridge or another appliance from which a little heat escapes. The mantelpiece above my woodburner works very well (I call it my built-in propagator!). They will also germinate on a sunny windowsill but may take a little longer to get going.

Tomatoes need to be kept well above freezing to survive. There’s no point trying to put them outside – or even into a greenhouse – until your last expected frost date has safely passed. Temperatures below 10ºC (50ºF) can result in slow growth and problems with flowering and fruiting. Click on the Plant List button in our Garden Planner to see recommended times for transplanting outdoors in your location.

I struggle to get a good crop outside, so I grow my tomatoes almost exclusively in my greenhouse. I’ve sometimes heard it said that transplanting into a greenhouse or polytunnel doesn’t require a hardening off period, but I prefer to ease them in gently by only putting them in there during the day for about a week before permanently transplanting. Alternatively, cover them up with horticultural fleece overnight for the first week or two to gradually acclimatise them.

Growing Tomatoes Outdoors

If you’re transplanting directly outdoors – a brave move in a cooler climate – you could try recycling plastic drinks bottles to create a shelter for young or low-growing tomato plants. Fill the bottles with water and surround the plant with them. The water absorbs heat during the day and releases it at night, keeping the plant in the middle that little bit warmer. You can buy products that perform the same function and which can be used around larger plants.

I took a few years off from growing ‘Latah’ while I explored other varieties, but none have so far met my expectations. Some produce more fruits – ‘Moneymaker’ stands out as being particularly prolific – but the flavour doesn’t quite match up. So I’ll be returning to ‘Latah’ for my next sowing of tomatoes, but also including one or two from the list above for comparison.