Last edited on 1 Nov 2026. View history
Guernsey Island Tomato
Guernsey Island Tomato
A variety of tomato
An indeterminate New Zealand heirloom from the Guernsey Islands, where it was grown commercially and sold across the British Isles, known all over Britain as the Guernsey tomato. Medium, round, streaky red and green fruit with top flavour but quite watery, best quartered in salads. A heavy cropper with excellent disease resistance. Needs staking. Sow in trays in late September, prick out at 3 cm, pot on at 10 cm and plant out at 10 to 15 cm high at 50 cm spacing, two rows per 1 m bed.
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Guernsey island tomato facts
Lifespan
Crop cycle
Max altitude
Optimal light
What are growing degree days?
A plant grows with warmth, not with days. A growing degree day is one day's worth of useful warmth: how many degrees the day's average temperature is above the lowest temperature the crop grows at. Add them up from planting and you know how far along the crop is, whatever the calendar says.
Say that lowest temperature is 10°C. A day averaging 17°C gives 7 growing degree days. A day averaging 8°C gives none, as it is too cold for the crop to grow. That is why the same lettuce takes about 50 days in a summer and 90 in an autumn: it needs the same total warmth either way.
For Guernsey Island tomato, the FAO EcoCrop database gives a lowest growing temperature of 7°C and a shortest growing cycle of 70 days at its best temperature, about 1155 growing degree days to a first harvest.
Where you've told us where your garden is, we use this and the weather there to predict when your Guernsey Island tomato will be ready to harvest. We don't use it for how long a plant lives or when it finishes: we go by what members have logged for that.
Growing Guernsey Island tomatoes
- Sow seeds indoors 6 weeks before planting out
- Harden off the seedlings 1 week before planting out
- Stake or cage the plants 1 week after planting out
- Water deeply 2 weeks after planting out every week
- Pinch out side shoots 3 weeks after planting out every 2 weeks
- Feed with tomato fertiliser 6 weeks after planting out every 2 weeks
- Check for first ripe fruit 1 week before first harvest
- Pull out finished plants 4 weeks after first harvest
Plant Guernsey Island tomatoes with
carrot
chives
black beauty eggplant
Video
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Ecological requirements
Data from the FAO EcoCrop database for Lycopersicon esculentum Mill.
| Family / Taxonomy | Magnoliopsida Asteridae Solanales Solanaceae |
|---|---|
| Life form | herb |
| Life span | annual |
| Habit | prostrate/procumbent/semi-erect |
| Optimal soil depth | shallow (20-50 cm) |
| Optimal soil texture | medium, organic |
| Optimal soil fertility | high |
| Optimal soil drainage | well (dry spells) |
| Optimal soil salinity | low (<4 dS/m) |
| Photoperiod | short day (<12 hours), neutral day (12-14 hours), long day (>14 hours) |
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