How to Grow Tomatoes in Ireland: Timing, Varieties and What Actually Works
Peter Dowdall, Irish horticulturist and broadcaster, explains how to grow tomatoes successfully in Irish conditions, covering the honest case for growing under cover, sowing timing, soil preparation, training, and managing blight in a wet Irish summer.
Growing tomatoes in Ireland
Tomatoes can be grown successfully in Ireland, but they require honesty about the conditions we are working with. The growers who get reliable crops have adapted their timing, variety choices and growing environment to the reality of the Irish season.
This is not a Mediterranean climate. Our summers are cooler, our light levels are lower, our humidity is higher and our growing season is shorter. None of that makes tomatoes impossible here. But it does mean that the approach which works elsewhere will not always translate directly to an Irish garden or greenhouse.
Tomatoes can be grown successfully in Ireland, but they require honesty about the conditions we are working with. This is not a Mediterranean climate. Our summers are cooler, our light levels are lower, our humidity is higher and our growing season is shorter than in the regions where tomatoes evolved and perform most naturally. None of that makes them impossible here, but it does mean that the approach which works in southern Europe, or which is described on most seed packets, will not always translate directly to an Irish garden or greenhouse. The growers who get good, reliable crops of tomatoes in Ireland are the ones who have adapted their timing, their variety choices and their growing environment to the reality of the Irish season rather than the instructions on the packet.
Indoor or outdoor: be honest about your climate
The most important decision you will make about growing tomatoes in Ireland is whether to grow them under cover or outdoors. In most parts of Ireland, and particularly anywhere west of the Shannon or north of a line through the midlands, growing tomatoes outdoors in the open ground is an unreliable proposition in most seasons. A good summer will produce a reasonable crop. A poor summer, with limited warmth and high humidity, will produce blight before your tomatoes have time to ripen.
A greenhouse, polytunnel, sunny porch or large south-facing conservatory changes this calculation entirely. Under cover, with the warmth that a glass or polycarbonate structure provides and the protection from rain that significantly reduces blight pressure, tomatoes become a reliable and rewarding crop across most of Ireland. If you are serious about growing tomatoes and do not have any form of covered growing space, that is the most valuable investment you can make before anything else.
Growing under cover
- Greenhouse, polytunnel, porch or south-facing conservatory
- Reliable crops across most of Ireland in most seasons
- Significantly reduced blight pressure from rain protection
- Earlier start and longer season than outdoors
- Essential in exposed, western or northern gardens
Growing outdoors
- Only reliable in sheltered, south-facing positions in warmer parts of Ireland
- Good summer: reasonable crop; poor summer: blight before ripening
- Choose blight-resistant varieties such as Ferline or Crimson Crush
- Never plant out before late May when all frost risk has passed
- Accept that some seasons will disappoint regardless of care
Sowing: earlier than the packet suggests
Most tomato seed packets recommend sowing in March or April. In Ireland, for anyone growing under cover, late February to mid-March is the right window. Tomatoes need a long season to establish, grow, flower, set fruit and ripen before the days shorten and temperatures drop in autumn. Starting too late compresses that season and reduces your crop.
Irish tomato growing calendar
Soil preparation and planting
Tomatoes are heavy feeders that thrive in fertile, well-drained, biologically active soil. Before planting into greenhouse borders or raised beds, work in generous amounts of well-rotted compost and improve the soil structure and biology at root level. Understanding what your soil is actually doing before you plant is worth doing: the advice on garden soil in Ireland covers the principles of soil structure, drainage and biological activity that apply directly to preparing for a demanding crop like tomatoes. Tomatoes planted into biologically active soil establish faster, feed more efficiently and tend to show greater resilience to the stress of a variable Irish summer.
Do not plant tomatoes in the same soil two years running. Rotation is important for this crop, as tomatoes are susceptible to soil-borne diseases that build up when the same ground is used repeatedly. Potatoes are in the same plant family and share the same rotation principles, including the shared blight risk. The advice on planting potatoes in Irish conditions is relevant reading here, particularly on drainage and soil management.
Plant deeply, burying the stem up to the lowest set of leaves. Tomatoes produce roots along any buried stem and a deeper, more extensive root system supports the plant through the demands of a long fruiting season. If you are growing in a raised bed, the guidance on raised beds in Ireland covers soil depth, drainage and preparation in full.
Build the soil before you plant
NutriChar is a certified organic biochar plant food, made using a patented process that locks nutrients into biochar structure rather than allowing them to wash away. Worked into greenhouse borders or raised beds before planting, it improves soil biology and moisture retention in the root zone across the full growing season. Tomatoes planted into soil treated with NutriChar establish faster and feed more efficiently through the demands of a long Irish fruiting season.
Training, feeding and watering
Most tomatoes grown in Irish greenhouses are cordon varieties, trained to a single stem by removing the side shoots that develop in the angle between the main stem and each leaf. These side shoots should be removed when small, snapped off cleanly with your fingers or cut with a clean blade. Left to develop, they produce a large, bushy plant with reduced fruit set and poor airflow, which in Irish humidity conditions significantly increases the risk of blight and grey mould.
Tie the main stem loosely to a cane or string support as it grows, and pinch out the growing tip in late July or early August once the plant has set four to six trusses of fruit. This stops the plant from investing further energy in stem growth and directs everything into ripening the fruit already set.
Once the first flowers appear, begin feeding weekly with a high-potash tomato fertiliser. Tomatoes in containers and growbags are entirely dependent on what you provide and should be fed consistently from first flower to final harvest. Water at the base of the plant rather than overhead, and aim for consistent moisture rather than alternating between dry and saturated conditions. Irregular watering is one of the most common causes of blossom end rot and split fruit in Irish-grown tomatoes.
Blight: understanding and managing the risk
Potato blight, caused by the organism Phytophthora infestans, affects tomatoes as well as potatoes and is a serious and recurring risk in the Irish growing season. It spreads rapidly in warm, wet, humid conditions and can devastate a crop within days of first appearing. The symptoms are dark, water-soaked patches on the leaves, rapidly turning brown, with white fungal growth visible on the undersides of affected leaves in humid conditions. Once blight takes hold in a plant, the fruit will also be affected and the crop is effectively lost.
The best approach to blight in Ireland is prevention rather than treatment. If you are dealing with a wider pattern of plant problems in your garden, the plant problems Ireland page covers the principles of diagnosis and ecological management that apply across crops. For tomatoes specifically, the preventive measures below are what matter most in practice.
Blight prevention: the practical approach
Good ventilation inside a greenhouse or polytunnel is the single most effective preventive measure. Blight thrives in still, humid air and struggles in moving air that dries the leaf surfaces between waterings. Open vents and doors on warm days, remove lower leaves as the fruit trusses ripen to improve airflow around the base of the plant, and avoid overhead watering at all times.
Do not grow tomatoes near potatoes if you can avoid it. If blight does appear, remove and dispose of affected material immediately, do not compost it, and harvest any fruit that is showing colour as it will continue to ripen indoors away from further infection. Choosing varieties with some blight resistance, such as Ferline or Crimson Crush, is a sensible precaution in particularly exposed or wet positions.
Questions gardeners ask about growing tomatoes in Ireland
Can I grow tomatoes outdoors in Ireland?
Yes, but with managed expectations. In a good Irish summer, a well-positioned outdoor tomato in a sheltered, south-facing spot will produce a reasonable crop. In a poor summer, blight will arrive before the fruit ripens. The further west or north you are, the less reliable outdoor tomatoes become. Choose blight-resistant varieties, plant in the warmest spot available, and accept that results will vary year to year. For a reliable crop in most seasons, growing under cover is the more dependable approach across most of Ireland.
When is it too late to sow tomatoes in Ireland?
For anyone growing under cover, late March is the latest practical sowing date for a full season crop. Plants sown in April will produce but the season will be compressed and fruit may not ripen fully before temperatures drop in autumn. For outdoor growing, where the season is even shorter, March is already late. Plants sown in May will struggle to ripen a useful crop before the first autumn frosts in most Irish gardens.
What are the best tomato varieties for Ireland?
For growing under cover, Gardener's Delight, Sungold and Ailsa Craig are reliable performers with good flavour and consistent cropping in Irish greenhouse conditions. For outdoor growing or any position with higher blight risk, choose varieties with built-in resistance: Ferline, Crimson Crush and Losetto have been bred specifically for resistance to Phytophthora infestans and perform noticeably better than standard varieties in wet Irish conditions.
My tomatoes have split fruit. What is causing it?
Split fruit is almost always caused by irregular watering: a period of dry conditions followed by heavy watering or rainfall causes the fruit to expand rapidly, splitting the skin before it can accommodate the sudden increase in moisture. The remedy is consistent watering at the base of the plant, keeping moisture levels as even as possible throughout the growing season. Mulching around the base of the plant helps retain soil moisture between waterings and reduces the fluctuations that cause splitting.
Can I save seed from my tomatoes to grow next year?
Yes, from open-pollinated or heritage varieties. Seed saved from F1 hybrid varieties will not reliably produce plants true to the parent, so it is not worth saving from those. To save seed, squeeze the pulp and seeds from a fully ripe fruit into a jar of water, leave for two to three days until the viable seeds sink and the pulp ferments and floats, then rinse and dry the seeds thoroughly before storing in a cool, dry place. Properly dried tomato seed will remain viable for three to four years.
That is the general picture
But your growing situation, your soil and your specific conditions will shape what works best for you. Tell Ask Peter what you are working with and get advice specific to your situation.
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