Types of Onions: Varieties, Uses, and Growing Tips

Sweet onions are a distinct class of onion prized for their mild, low-pungency flavour and high water content, which makes them pleasant to eat raw and ideal for cooking down into sweet, golden caramelised dishes. Alongside the common bulb onion, gardeners grow several other types of onion that have earned wide use in cooking thanks to their qualities. The properties of onion as a medicinal plant are well known. This guide covers what sweet onions are, the main varieties and growing regions, how to store and cook them, and the practical cultivation and care of each type of this valuable vegetable crop.

What sweet onions are: definition and characteristics

Sweet onions are onions bred for a low concentration of the sulphur compounds that make ordinary onions sharp, combined with a high water and sugar content that gives them a mild, almost fruity taste. Unlike storage (yellow) onions, sweet onions have thin, pale skins, a flattened or globe shape, and flesh juicy enough to eat raw in slices.

The difference between sweet onions and regular storage onions comes down to chemistry rather than added sugar. Sweet onions are not sweeter because they contain more sugar than a typical yellow onion; they taste sweeter because they contain far less of the pungent sulphur compounds, so the natural sugars are no longer masked. Their higher water content further dilutes the sharp notes, which is also why sweet onions bruise easily and do not keep as long.

Onions make people cry because cutting them ruptures cells and releases enzymes that convert sulphur compounds into a volatile irritant (syn-propanethial-S-oxide) that drifts up to the eyes. Sweet onions, with their lower sulphur content, produce noticeably less of this irritant, so chopping them brings fewer tears and less need to reach for a Kleenex.

In nutritional terms sweet onions are low in calories and provide vitamin C, vitamin B6, folate, potassium and dietary fibre, along with antioxidants such as quercetin. Their distinguishing trait remains the flavour profile: mild, juicy and sweet, which shapes how they are best used in the kitchen.

Sweet onion varieties and regional origins

Sweet onions are sold under many regional names, and most owe their character to a specific climate and soil rather than to one botanical variety. The best-known American sweet onions include the Vidalia onion from Georgia, the Walla Walla Sweets from Washington, the Texas 1015 Supersweets, the Maui onion from Hawaii and the Imperial Valley Sweets from California. European growers add their own protected varieties from France, Spain and Italy.

Comparison of popular sweet onion varieties

The main sweet onion varieties differ chiefly in their growing region and peak season, which in turn determines when each appears in shops. The table below compares the leading types.

Other US sweet onions worth knowing include the Mattamuskeet Sweets and other Texas Sweet onions, the Sweet Imperials, and the historic Bermuda onion and Pecos onion. Red onions and standard yellow onions, by contrast, are storage onions with sharper flavour and longer shelf life.

European sweet onion varieties

Europe contributes several prized sweet onions, most of them carrying Protected Designation of Origin (PDO) status that ties the name to a defined area. From France comes the Oignon doux des Cévennes; Spain offers the Cebolla Dulce de Fuentes; and Italy is known for the Cipolla Rossa di Tropea Calabria, a sweet red variety. These legal protections work much as the Vidalia rules do in the USA, restricting the name to onions actually grown in the designated region.

The Bermuda onion: history and characteristics

The Bermuda onion is one of the earliest sweet onions to gain a commercial reputation, named for the island of Bermuda from which seed was historically traded. It is a flat, mild, pale onion that helped popularise the idea of an onion grown specifically for sweetness, and its lineage feeds into several later American sweet types grown in warm, mild-winter regions.

Breeding and selection history of sweet onions

The history of sweet onions is a story of regional accident and deliberate breeding. The Vidalia onion began by chance in 1931 when farmer Moses Coleman discovered that onions he grew near Vidalia, Georgia, turned out unexpectedly mild; the variety later gained legal protection and is overseen by the Vidalia Onion Committee. The Walla Walla sweet onion traces to seed brought from the island of Corsica by Peter Pieri and developed by Italian immigrant growers in Washington.

The Texas 1015 Sweet Onion was developed scientifically at Texas A&M University by Dr. Leonard Pike (Leonard M. Pike), whose team bred a mild, disease-resistant onion for the Rio Grande Valley. Its name comes from its ideal planting date — October 15 — which is why it is also sold as the Texas 1015 Supersweets and known simply as the 1015 onion. This work in the 1980s is a landmark in the 1015 Texas onion development story and shows how modern sweet onions combine climate with targeted plant breeding.

Growing regions and seasonal availability of sweet onions

Sweet onions are available almost year-round because different regions harvest in different months, with the Southern Hemisphere filling the winter gap. Spring and early summer bring Georgia's Vidalia, Texas's 1015 and Hawaii's Maui onions; mid to late summer adds the Walla Walla onions from Washington. Knowing the season helps with both quality and price, since each variety is sweetest when freshly harvested.

• Spring: Vidalia (Georgia), Texas 1015 (Rio Grande Valley), early Maui Sweets (Hawaii).
• Summer: Walla Walla Sweets (Washington), continuing Maui onions.
• Autumn: California Imperial Valley Sweets and late domestic supplies.
• Winter: OSO Sweet and similar onions imported from Chile and Peru in the Southern Hemisphere.

To select quality sweet onions, choose bulbs that are firm and heavy for their size with dry, papery skins and no soft spots, sprouting or green shoots. Sweet onions can be bought online from specialist growers and produce suppliers such as Melissa's and Pittman & Davis, who ship seasonal and organic sweet onions and offer them as gift boxes; certified organic sweet onions are grown without synthetic pesticides and labelled with their organic certification.

Growing sweet and other onions in the garden

On allotments and home gardens, the bulb onion is grown most often, with shallot (Kubansky type) and Welsh onion (batun) common in some villages. Each of the following onion types has its own planting method and care routine.

Onion sets: planting and care

Onion sets are grown from black onion seed (chernushka) and serve as the planting stock for bulb onions. The seeds are best pre-germinated over 3–4 days; once they have chitted, place them in cold storage at 0–1°C and hold them there for 10–15 days before sowing. Such seeds must only be sown into moist soil.

Sets should be planted densely, leaving 10–15 cm between rows, or in 8–10-row bands with 7–8 cm between the lines. The seed rate is up to 8–10 g/m², with a sowing depth of 3–4 cm on light soils and 2–3 cm on heavy ones. The smaller the set (its diameter should be 1–2 cm), the better it stores over winter. For this reason thinning is not carried out.

Further care of onion sets consists of regular weeding and loosening of the soil. By early August the foliage flops over; it is then pulled up and dried well. Sets must be stored in a dry place at 20–28°C or in a refrigerator at minus 1–3°C. If these conditions are not met, many plants will run to seed and the yield of mature bulbs will fall.

The following spring, sets are planted early — in mid to late March. Use single rows with 20–25 cm between them, or triple rows at the same spacing, leaving a 45 cm path after every three rows and 6–8 cm between plants in the row. Subsequent cultivation matches that of growing bulb onions from seed. If flower stalks appear they should be snapped off while still rudimentary.

Spring onions: early greens for the table

Spring onions provide early greens for the table. They are easy to grow in a living space, in a cold frame, under film cover, or in open ground. Outdoors, bulbs are best planted in autumn 15–20 days before the first frosts, so they have time to establish but not to form leaf.

Planting depth is 8–10 cm. Use smaller bulbs, the so-called cull bulbs of 3–4 cm diameter. Before hard frosts the bed is covered with a 10 cm layer of manure, which is removed in spring after the thaw.

Onions can also be planted in early spring. Press large bulbs into the soil 1–2 cm apart, then feed with 30–40 g of ammonium nitrate per square metre followed by watering. Leaf growth is vigorous at plus 20–22°C.

From the start of leaf emergence the produce will be ready in 20–25 days. When planting stock is scarce, green leaf can be raised from bulb bases: the upper part is cut off for eating, while the lower part — about 1.5 cm from the bulb base — is planted into the soil.

Growing onion seed

Onion seed can be grown in your own garden, but first take care that different varieties do not cross-pollinate. Undamaged bulbs are planted 15–20 days before the autumn cold sets in, at a depth of 8–10 cm. They can also be planted in early spring.

The planting scheme is 25×25 cm. Care must be very thorough: watering, weeding, feeding, and tying the flower stalks to stakes. Once the plants have finished flowering it helps to lift them slightly to speed ripening. They are then cut, or the whole seed heads dug up, bundled and hung under a shelter to dry.

After about a month the heads are broken up and dried. In a dry, ventilated room at 6–10°C the seeds keep their germination for 2 years. On household plots and gardens it is mainly bulb onion that is grown, with Kubansky shallot and Welsh onion in some villages.

Shallot (sorokozubka)

Shallot (sorokozubka) in its first year from sowing forms 4–5 small set-like bulblets weighing 25–30 g each. Plant them in mid-October and by early May you can harvest green leaves.

They form in abundance and have higher culinary quality than the leaf from bulb onions. For summer use, plant shallot in early spring. The cultivation is the same as for bulb onion. Welsh onion grows in one place for 3–4 years.

Sowing by seed can be done in spring, summer or autumn. With the first and second sowing dates, it yields tender green leaves as early as April the following year. Over the summer they can be cut several times. Care is simple: weeding, loosening, watering, feeding, removing flower stalks.

Chives

Chives are grown for their tender leaves. The foliage regrows in early spring. A spring sowing gives produce in July–August. Use 20 cm between rows and 5–6 cm in the row, with a seed rate of 1.5–2 g per 1 m². Care is the same as for Welsh onion.

Tree (multi-tier) onion

The tree onion is a perennial cultivated for its leaf and small aerial and underground bulblets. From the aerial bulbs (bulbils) new stems develop, on which a new tier of bulbils forms.

Over the summer up to 3–4 tiers develop. The lower-tier bulbs are 1.5–2.5 cm in diameter, with smaller ones higher up. Sowing is done in spring and summer. The harvest is taken 5–7 days earlier than from Welsh onion.

Leek

Leek is a biennial plant. In its first year it forms a false stem — the shank — which is the part eaten. In young plants the leaves are also used. There are many varieties, and the right selection makes it possible to obtain green produce year-round. The yield is 2–3 times higher than that of bulb onion.

Sow for transplants in late February and plant out into open ground after frosts have ended. By then the plants are pencil-thick and about 25 cm tall. For autumn produce and winter storage, sow in late March directly into the ground.

Plants are spaced 20–30 cm between rows and 8–10 cm in the row. As usual, they need watering, loosening and feeding. Leek is harvested in late autumn. Plants can be left over winter, but must be earthed up or covered with other materials. It is widely used in all kinds of dishes.

Leek also has uses in medical practice. It is one of the most valuable types of onion.

Siberian onion (slizun)

Siberian onion (slizun) is a perennial rhizomatous plant that contains many vitamins and minerals, especially iron. It is propagated by seed and by transplants. When sown from seed it forms a clump of 4–5 plants in the first year, and by the end of the second year has up to 20 with a huge number of leaves. It is used in cooking, going into marinades and seasonings.

How to store sweet onions

Sweet onions should be stored cool, dry and well separated, because their high water content makes them spoil far faster than storage onions. Kept at room temperature in a single layer with good air flow, most sweet onions last only a few weeks, against many months for yellow storage onions.

• Temperature: store at around 4°C in the refrigerator for longest life, or in a cool, dark pantry for short-term use.
• Humidity: keep humidity moderate; excess moisture promotes rot, so avoid sealed plastic bags.
• Air flow: spread bulbs out so they do not touch, ideally in a mesh bag or an open basket; some growers wrap each onion in paper towel and refrigerate.
• Long-term: peeled, chopped sweet onions freeze well for several months and are excellent for later cooking, though they lose their crispness for raw use.

A classic tip is to hang sweet onions in the legs of clean pantyhose, tying a knot between each bulb, which keeps them apart and ventilated. Do not store sweet onions next to potatoes, as the moisture and gases each gives off hasten spoilage in the other.

Culinary uses of sweet onions

Sweet onions are at their best where their mild, juicy flavour can shine — raw in salads and on sandwiches, or cooked slowly until deeply caramelised. Because they lack the harsh bite of storage onions, sweet onions are the natural choice for raw consumption, for grilling whole, and for any dish built around caramelised onion.

Caramelising sweet onions draws out their natural sugars into a soft, golden, jam-like result. Slice the onions thinly, cook them gently in butter or oil over low to medium heat, and stir patiently for 30–45 minutes until they turn amber; their high sugar content means they caramelise more readily than ordinary onions. Caramelised sweet onions are the heart of French onion soup, onion tarts and burger toppings.

For grilling, thick rings or halved onions brushed with oil develop a smoky sweetness over the coals, making them a summer favourite alongside grilled meats and vegetables. Raw, thin slices of sweet onion add gentle bite to sandwiches, burgers, salads and pizza without overpowering other ingredients. When a recipe calls for raw onion and you want a milder result, a sweet onion is the simplest substitution for a yellow or red onion.

Recipes with sweet onions

Sweet onions pair naturally with summer produce, especially fresh tomatoes, herbs and seafood. A shrimp, sweet onion and couscous salad is a good warm-weather example: combine cooked couscous, sautéed or grilled shrimp, thin slices of raw sweet onion, diced fresh tomato, chopped herbs and a lemon-olive oil dressing for a light, balanced dish. Sweet onions also work well in dips and appetizers, blended into a creamy sweet onion dip served with crackers or vegetables.

• Side dishes: whole sweet onions roasted until tender, or quick-pickled rings to brighten rich plates.
• Soups and salads: raw in green and grain salads, or simmered into onion soups.
• Pizza and quiche: caramelised sweet onion as a topping or quiche filling.
• Burgers and sandwiches: raw rings or grilled slices as a topping.

French-style onion recipes

French onion soup is the signature dish that shows off caramelised sweet onions, building a deep flavour from onions cooked slowly until brown, then simmered in beef stock and finished with toasted bread and melted cheese. The same caramelised base inspires French-style onion tarts and quiches, where sweet onions are paired with cream, eggs and cheese in a pastry shell. These dishes rely on the onion's sugars rather than added sweeteners.

Appetizers and dishes featuring sweet onions

Sweet onions feature on many restaurant menus, including The Sweet Onion Restaurant in Downtown Waynesville, North Carolina, near the Blue Ridge Mountains, which builds regional and contemporary Southern cuisine around fresh, locally sourced ingredients. Such kitchens use sweet onions across appetizers, salads and entrees — from onion-topped starters to mains paired with mountain trout, fresh seafood, southern fried chicken and seasonal vegetables — and round out the experience with house-made desserts and a drinks list of red and white wine, sparkling wine, beer, and handcrafted cocktails and non-alcoholic drinks. The point for the home cook is the same: sweet onions belong everywhere from a simple dip to a full dinner.

Onion as a medicinal plant: beneficial properties

Onion has long been valued as a medicinal plant as well as a food, and many of its benefits carry over to sweet varieties. Onions of all kinds are rich in vitamins, minerals and antioxidant compounds, and the Siberian onion (slizun) is noted for its high iron content. Their natural sulphur compounds and flavonoids such as quercetin are associated with supporting the immune system and general well-being.

Leek and other onion types also have recognised uses in folk medical practice, which is part of what makes the onion family one of the most valuable groups of vegetable crops for both the kitchen and health. For those who enjoy growing and cooking, exploring sweet onion varieties alongside the hardy garden types above is a rewarding way to get the most from this versatile plant.