Step-by-step Guide to Growing Tomatoes in Ireland
Anthony holding a Tomato Pineapple Ananas
Growing tomatoes from organic and chemical-free seeds is rewarding, as there is nothing like the taste of a homegrown tomato. At Fat Tomato, we grow over 100 varieties of heritage and heirloom tomatoes that vary in colour, size, and flavour. Most are grown indoors in our polytunnel; a few are sown outside in raised beds.
We hand-select a few to save seeds each year and sell them on our online store. Check them out here.
Here's a step-by-step guide to help you grow healthy, delicious tomatoes:
1. Choose the Right Tomato Variety
Determine your needs: Consider the type of tomato (cherry, plum, salad, globe, beefsteak or oxheart) based on your space, microclimate climate, and taste preferences. If you can only grow tomatoes outdoors, select varieties that do not mind getting wet now and again in the Irish weather and will ripen without the need for heat in a polytunnel or glasshouse. If you can only grow in pots, pick the right variety. We recommend growing smaller tomatoes as they will ripen quicker.
Organic seed source: Purchase organic / chemical-free tomato seeds from reputable suppliers or your local garden centre. Look for heirloom or certified organic open-pollinated varieties. We do not grow F1 varieties at Fat Tomato as some tend to bring disease, and you cannot save seeds from them.
Check out 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 6–8 weeks before your last expected frost date. In most areas in Ireland, this will be around May. So we start sowing tomatoes in February/March on our heated bench in our polytunnel. You can sow tomatoes from seed until May; pick some late-season varieties to grow. What we do is sow tomatoes a few times from February to April, so we have 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 - we mix some into the seed compost as it soaks up water like a sponge and releases it when the compost is dry
A spray bottle or watering can
Heated mat/bench (optional)
Grow lights (if you do not have access to natural light)
Clear plastic cover or plastic wrap (optional for humidity)
3. Prepare the Seed Starting Mix
Soil mix: Mix a handful of vermiculite into the organic peat-free seed compost, just enough to see flecks of it. Fill your seed-starting tray or pots with the mix.
Moisten the mix: Lightly moisten it before sowing, but avoid soaking it.
4. Plant the Seeds
Sowing depth: Place tomato seeds about .5 cm deep into the soil.
Spacing: If using a seed tray, plant seeds 2 cm apart. If using individual pots, plant 2-3 seeds per pot.
Cover: Lightly cover the seeds with a thin layer of soil mix.
Labels: Label the tomato variety with a sowing date on the back.
5. Create Ideal Growing Conditions
Temperature: Tomato seeds germinate best at temperatures between 20°C and 27°C. Use a heat mat or bench if needed to maintain consistent warmth. Of course, you can place them on the window sill that gets some sun—just make sure the trays do not dry out quickly.
Humidity: To help retain moisture, cover the trays with a plastic dome or plastic wrap. Once the seeds have germinated, remove the cover.
Light: Once the seeds sprout, they need 12-16 hours of light daily. If you are growing indoors, use grow lights to provide this. Keep the lights just 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 waterlogged. Use a spray bottle to mist the soil to avoid displacing the tiny seeds gently. Once the seedlings are a bit larger, water the base of the plant, ensuring not to wet the leaves too much. Tomato plants hate getting wet!
7. Transplanting into Larger Pots
When to transplant: When seedlings develop 2-3 sets of true leaves and the roots are well-established, they can be transplanted into larger pots.
Potting up: If using individual pots, transplant seedlings into small-medium pots to give them more room to grow. One seedling per pot. Just be careful not to break the roots. If your tomatoes are tall and leggy, you can bury some of the stem in the compost. Tomatoes can form roots along their buried stems, helping them develop a stronger root system.
We usually do not place them back on the heated mat/bench, depending on the weather.
8. Harden Off the Seedlings
Acclimatisation: Harden the tomatoes off about 7-10 days before you plant them in their final position. Gradually introduce the seedlings to outdoor conditions. Start by placing them in a shaded, sheltered spot for a few hours each day, then slowly increase the time spent outdoors and exposure to sunlight.
9. Prepare the Garden Bed or Containers
Site selection: Choose a sunny spot with well-drained soil. Tomatoes need at least 6-8 hours of direct sunlight each day.
Soil preparation: If planting directly in the garden, work in organic compost or well-rotted manure to improve soil fertility. If planting in containers, ensure they are deep enough and have good drainage. Tomatoes grow deep roots, so we suggest big pots at least 50 cm deep.
Spacing: Space the plants 50 cm apart for determinate (bushy) varieties and 60 cm apart for indeterminate (vining) varieties.
10. Plant the Seedlings
Plant deep: When transplanting, bury the seedlings deeper than they were in their pots, covering the stem to the first set of leaves. Tomatoes can form roots along their buried stems, helping them develop a stronger root system.
Label: Make sure you label them.
Water well: After planting, water the seedlings well to settle the soil around the roots.
11. Support the Plants
Staking or growing up string: Use stakes or strong string to keep the plants upright and prevent them from sprawling on the ground. This helps avoid disease and makes harvesting easier. We use twine here at Fat Tomato, whereby we tie it to wire on the roof of the polytunnel and bury the end piece under the tomato when plating them out.
Tie gently: As the plants grow, tie the stems loosely to the support structures with soft garden twine or fabric strips.
12. Ongoing Care and Maintenance
Watering: Water consistently, aiming for deep, infrequent watering to encourage strong roots. Avoid getting water on the leaves to reduce the risk of fungal diseases. We usually water tomatoes every second day until they start to produce fruit. Then we do it every fourth day as we want our tomatoes to taste delicious, not watery.
Mulch: To help retain moisture and suppress weeds, apply a layer of organic mulch (straw, grass clippings, sheep wool, or shredded leaves) around the base of the plants.
Fertilising: If the soil lacks nutrients, apply organic fertiliser every second week. We use a mixture of homemade Comfrey feed and organic seaweed fertilisers.
Pruning: For indeterminate (vining) varieties, pinch off suckers (the small shoots between the main stem and branches) to encourage strong main stems and better airflow. When they reach a certain height, we stop them from growing by cutting off the top so they can put all their energy into producing fruit. Place the prunings into your compost bin. Some people say you cannot compost tomato leaves, but you can in a healthy compost heap.
Tomatoes growing in our polytunnel with French marigolds
13. Pest and Disease Management
Inspect regularly: Look for pests such as aphids, whiteflies, and tomato hornworms. We use the companion planting method to control pests, sowing basil, nasturtiums, and marigolds between the tomatoes.
Disease prevention: Pruning and proper spacing around the plants ensure good airflow. Avoid overhead watering to reduce the risk of fungal diseases like blight.
14. Harvesting
When to harvest: Tomatoes are ready to pick when fully coloured and slightly soft to the touch. Some varieties ripen to red, while others may be yellow, orange, purple or black when ripe.
Harvesting method: Cut the fruit from the vine using garden scissors or pruners, leaving a small part of the stem attached.
15. Post-Harvest Care
Storage: Store harvested tomatoes at room temperature, away from direct sunlight. Never place tomatoes in the fridge as the flavour and texture changes.
Preserve: If you have a large harvest, you can freeze overripe tomatoes for the winter and use them in soups, stews, and sauces. At Fat Tomato, we make many delicious things with tomatoes, from chutneys to jams and sauces. Check out our shop here.
16. END OF SEASON
Clear beds: We start to clear tomato vines by composting them when we have picked all the fruit.
Green tomatoes: At the end of the season, you will always have a handful of tomatoes that do not ripen on the vine. Bring them inside and place them on a tray on some brown paper, not touching each other with a banana, and they will ripen over time. You can also make some green tomato chutney.
By following this step-by-step guide, you will be well on your way to growing a successful crop of organic, chemical-free tomatoes.
If you start sowing tomatoes late or they do not germinate due to weather conditions, do not panic. We always have many tomato plants to spare and sell them at our Honesty Farm Shop from May onwards. Keep an eye on our social media pages for when they are ready.
If you have any questions, reach out to us.