Step-by-step Guide to Growing Tomatoes in Ireland
Anthony O’Toole, founder of Fat Tomato, holding a Tomato Pineapple Ananas
There’s nothing quite like the taste of a homegrown tomato. At Fat Tomato, we cultivate over 100 heritage and heirloom tomato varieties, showcasing their different colours, sizes, and flavours. Most of our plants are grown in our polytunnel, while a select few thrive outside in raised beds. We exclusively grow from organic, chemical-free seeds - they’re easier to cultivate and, more importantly, produce the most flavourful tomatoes.
Each year, we hand-select a few favourites to save seeds from, which we then offer for sale through our online store. Check them out here.
Here's a step-by-step guide to help you grow delicious tomatoes:
1. Choose the Right Tomato Variety
Start by identifying your needs: Depending on your available space, local microclimate, and flavour preferences, Think about the type of tomato you’d like to grow—cherry, plum, salad, globe, beefsteak, or oxheart.
Growing outdoors: Choose varieties that can tolerate a bit of wet and will ripen without the additional warmth of a polytunnel or greenhouse — a must in the unpredictable Irish weather.
Limited to pots: Go for smaller, quicker-ripening tomatoes. We recommend cherry varieties like Latah, Clementine, Yellow Submarine for their speed and flavour.
Organic seed sources: Buy organic, chemical-free seeds from trusted suppliers — either online or at your local garden centre. Prioritise heirloom and open-pollinated varieties. At Fat Tomato, we don’t grow GM or F1 seeds. Why? F1s can sometimes carry disease and do not taste great, and you cannot save seeds from them.
Browse our open-pollinated, chemical-free seed collection on our online store here.
Other Irish seed suppliers: Check out Brown Evenlope Seeds and Irish Seed Savers.
2. Prepare for Indoor Seed Starting
Timing: Start seeds indoors 6 to 8 weeks before your last expected frost date. In most areas of Ireland, this falls around May. At Fat Tomato, we start sowing in February/March on a heated bench in our polytunnel. You can sow tomatoes up until May — just choose some late-season varieties. We sow in small batches from February to April to ensure a steady supply of tomatoes right up to November.
Supplies needed:
Organic, chemical-free tomato seeds
Seed starting trays or small pots
Seed labels
Organic peat-free seed compost
Organic peat-free potting compost
Vermiculite – mix into the seed compost to help retain and release moisture
Spray bottle or watering can
Heated mat or bench (optional but ideal for consistent warmth)
Grow lights (if natural light is limited)
Clear plastic cover or cling film (optional, for humidity)
3. Prepare the Seed Starting Mix
Soil mix: Mix a handful of vermiculite into your organic peat-free seed compost. You should be able to see small flecks of it in the mix.
Seed trays: Fill your seed trays.
Moisten the mix: Lightly dampen the compost before sowing. It should be moist, not soggy.
4. Plant the Seeds
Sowing depth: Sow tomato seeds approximately 0.5 cm deep.
Spacing: In trays, space seeds 2 cm apart. In small pots: sow 2–3 seeds per pot.
Cover: Lightly cover the seeds with a thin layer of the soil mix above.
Labels: Always label each variety and include the sowing date on the back.
5. Create Ideal Growing Conditions
Temperature: Seeds germinate best at 20°C - 27°C. If available, use a heat mat or heated bench. A sunny windowsill will also work - check regularly to prevent the compost from drying out.
Humidity: To retain moisture, cover the trays with a plastic dome or cling film. Remove the cover once the seeds have germinated.
Light: Seedlings need 12–16 hours of light daily after germination. If indoors without much natural light, use grow lights.
Keep lights a few centimetres above the seedlings to prevent stretching.
Tomato seedlings in tray
6. Watering and Care
Watering: Keep the soil lightly moist but not soggy. Use a spray bottle to mist the surface gently to avoid disturbing tiny seeds. Once seedlings grow larger, water at the base of the plant—try not to get the leaves wet, as tomato plants dislike it!
7. Transplanting into Larger Pots
When to transplant: Once seedlings have 2 - 3 sets of true leaves and strong root development, they’re ready to move to larger pots.
Potting up: Transplant each seedling into an individual small-to-medium-sized pot. Handle with care to avoid damaging the roots. If your seedlings are leggy, you can bury part of the stem in the compost — tomatoes grow roots from buried stems, strengthening the plant. We don’t usually return them to the heated bench at this stage, unless the weather is unusually cold.
8. Harden Off the Seedlings
Acclimatisation: Begin hardening off around 7 = 10 days before planting out. Gradually expose seedlings to outdoor conditions by placing them in a sheltered, shaded area for a few hours each day. Increase their time and light exposure gradually to help them adjust without stress.
9. Prepare the Garden Bed or Containers
Site selection: Choose a sunny location — tomatoes need 6 - 8 hours of direct sunlight daily. Good drainage is essential.
Soil preparation: For in-ground planting, enrich the soil with organic compost or well-rotted manure. For containers, ensure they’re deep (at least 50 cm) and offer proper drainage. Tomatoes have deep root systems and thrive in larger pots.
Spacing:
Determinate (bushy) varieties: space 50 cm apart
Indeterminate (vining) varieties: space 60 cm apart
10. Plant the Seedlings
Plant deep: Bury the seedlings deeper than they were in their pots, up to the first set of leaves. This encourages additional root development along the buried stem.
Label: Label each plant clearly with its variety.
Water well: After planting, water thoroughly to settle the soil around the roots.
11. Support the Plants
Staking or stringing: Use stakes, canes, or string supports to keep plants upright and off the ground — this improves airflow, reduces disease, and makes harvesting easier. At Fat Tomato, we use twine tied to wire on the roof of the polytunnel, burying the other end under the tomato when planting.
Tie gently: As plants grow, loosely tie stems to supports using soft garden twine or fabric strips to avoid damage.
12. Ongoing Care and Maintenance
Watering: Water consistently — deep and less frequent watering encourages strong roots. Avoid wetting the leaves to prevent fungal problems. We water every second day until fruiting begins, then switch to every fourth day to concentrate flavour (watery tomatoes are no good!).
Mulching: Apply a layer of organic mulch (straw, grass clippings, sheep wool, or shredded leaves) to help retain moisture and suppress weeds.
Fertilising: Feed fortnightly if needed, using organic fertilisers. We use a mix of homemade Comfrey tea and organic seaweed feeds.
Pruning: For indeterminate varieties, remove side shoots (“suckers”) from where branches meet the main stem to encourage airflow and direct energy into fruit production. Once plants reach the desired height, pinch off the growing tip to stop vertical growth and boost fruiting. Add pruned leaves and stems to your compost heap — despite common myths, healthy tomato leaves can be composted without issue.
Tomatoes growing in our polytunnel with French marigolds
13. Pest and Disease Management
Inspect regularly: Check your plants frequently for common pests such as aphids, whiteflies, and tomato hornworms.
At Fat Tomato, we use companion planting to naturally deter pests — sowing basil, nasturtiums, and marigolds between the tomato plants.Disease prevention: Maintain good airflow by pruning and spacing your plants well. Avoid overhead watering to reduce the risk of fungal diseases like blight.
14. Harvesting
When to harvest: Tomatoes are ready to pick when they are fully coloured and slightly soft to the touch.
Remember, not all tomatoes ripen red — some turn yellow, orange, purple, or even black.Harvesting method: Use garden scissors or pruners to gently cut the fruit from the vine, leaving a small part of the stem attached.
15. Post-Harvest Care
Storage: Store your tomatoes at room temperature, out of direct sunlight.
Never refrigerate them — cold temperatures can ruin both flavour and texture.Preserve: If you end up with a glut, freeze overripe tomatoes for winter use in soups, stews, or sauces.
At Fat Tomato, we turn our harvest into everything from chutneys and jams to rich tomato sauces. Check out our shop here.
16. End of Season
Clear beds: Once all fruit has been picked, remove and compost the spent vines.
Green tomatoes: It’s normal to have a few green tomatoes left at the end of the season. To ripen them indoors, place them on a tray lined with brown paper, spaced out so they’re not touching. Add a ripe banana to speed up the process. Alternatively, turn them into a delicious green tomato chutney!
By following this step-by-step guide, you'll be well on your way to growing a bountiful crop of organic, chemical-free tomatoes — full of flavour and perfect for the Irish climate.
And remember: If you’re running behind or your seeds don’t germinate (it happens!), don’t worry. We always grow more than we need. From May onwards, you’ll find healthy tomato plants available at our Honesty Farm Shop.
Keep an eye on our social media pages for updates on availability.
Have a question or need advice? Get in touch — we’re happy to help!