Fuentes Sweet Onion - Complete Growing and Care Guide

Variety: Sweet from Fuentes

Allium cepa

About this Crop

The Fuentes Sweet Onion is a traditional Spanish variety originating from Fuentes de Ebro, in the province of Zaragoza (Aragón), where it has been grown since time immemorial on the fertile floodplains of the River Ebro. Belonging to the Amaryllidaceae family, it is renowned for its exceptionally sweet flavour and crisp, juicy texture, making it suitable for raw consumption without the pungency and sharpness characteristic of other onions.

The plant forms a large globe-shaped bulb, which can reach 400-600 grams. The outer skin is a straw-white colour, thin and shiny, and the inner layers are white, thick, crisp and very juicy. Unlike other varieties, its rings are thick and separate easily. The leaves are long, hollow and medium green.

The secret of its sweetness lies both in the genetics of the variety and in the terroir of Fuentes de Ebro: rich alluvial soils, the riverside microclimate and the Ebro water create conditions that no other area has been able to replicate fully. In fact, the Fuentes Sweet Onion is protected by a quality mark and is celebrated annually at food fairs and gastronomic events in Aragón.

History & Origin

The Fuentes Sweet Onion is the horticultural pride of Fuentes de Ebro, a municipality on the banks of the Ebro a few kilometres from Zaragoza. Its cultivation has been documented for centuries and it is an example of how a local variety can achieve fame and recognition beyond its region thanks to exceptional organoleptic quality.

The secret of its sweetness is twofold: on the one hand, the genetics of the variety, selected over generations by Fuentes growers to obtain ever sweeter and more tender bulbs. On the other, the terroir: the deep alluvial soils of the Ebro floodplain, rich in silt and well-drained, combined with the microclimate and water quality, create unique growing conditions. It is said that the same seeds grown outside this area do not produce onions with the same degree of sweetness.

Today, the Fuentes Sweet Onion is a gourmet product that stars at food fairs, is sought after by top restaurants and has become an emblem of quality traditional Aragonese agriculture.

Ideal Companions

CarrotLettuceTomatoBeetrootCalendulaChamomile

Avoid

Green beanPeaCabbageOther onions in the same bed

Superfood

The Fuentes Sweet Onion shares the nutritional profile of onions: it is rich in water (approximately 89%), fibre and sulphur compounds such as allicin, with antibacterial and anti-inflammatory properties. It provides vitamin C, vitamin B6, folic acid and minerals such as potassium, manganese and phosphorus. Its content of quercetin, a powerful flavonoid antioxidant, is significant and concentrated in the outer layers of the bulb. Per 100 g it provides about 40 kcal, making it a light and healthy food.

Preservation

Being a very juicy onion with a high water and sugar content, its post-harvest shelf life is shorter than that of other onion varieties. It keeps for 2 to 4 months in a cool, dry, dark and well-ventilated place, hung in strings or spread out in wooden crates. Do not store near potatoes (the gases from both accelerate their mutual deterioration). For longer preservation, it can be frozen chopped in portions or dehydrated into thin slices for use as a seasoning.

Pest Monitoring

Pay special attention to: Onion fly, thrips, downy mildew, white rot, leek moth.

FAQ

Why doesn't it sting at all?: The low content of volatile sulphur compounds (responsible for the sting and tearing when cutting onions) is a genetic characteristic of this variety, enhanced by the growing conditions of Fuentes de Ebro. It is perfect for eating raw.
Can it be grown outside Fuentes de Ebro?: Yes, the variety will grow and produce edible bulbs in any area with suitable conditions (loose soil, mild climate, moderate watering). However, the extreme sweetness that characterises onions grown in Fuentes de Ebro may not be fully achieved outside its original terroir.
How long does it last once harvested?: Between 2 and 4 months under good storage conditions (cool, dry, dark, ventilated). Being juicier than other varieties, its shelf life is shorter. To extend it, make sure it is well cured in the sun before storing.
Why do they bolt?: Bolting (flowering) in onions is usually caused by cold stress during cultivation, especially if planted too early and subjected to a prolonged cold spell, or by abrupt temperature fluctuations. Planting at the right time and choosing varieties suited to the area reduces the risk.

Notas

The Fuentes Sweet Onion is much more than a vegetable: it is living history of Aragonese horticulture and a reminder that terroir is not a concept exclusive to wine. Its sweet flavour and crisp texture make it a unique ingredient that elevates any dish. Growing it in our garden is a tribute to generations of farmers who for centuries selected and improved this jewel of the Ebro riverbank. If grown alongside other onion varieties, bear in mind they may cross-pollinate if they flower, though onions are normally harvested before flowering.

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