Table of Contents
- The Onion Story: How One Crop Spread Across the World
- What Is an Onion? Understanding the Allium Family
- The Major Onion Groups Grown Worldwide
- Why Onion Varieties Are Different: Day Length and Bulb Formation
- Sweet Onions vs Storage Onions: Why Flavor Changes
- Onion Colors and What They Actually Mean
- Onion Varieties by Region of the World
- Famous Onion Varieties and Why They Matter
- Why There Are Hundreds of Onion Varieties Worldwide
- How to Choose the Right Onion Variety for Garden and Kitchen Use
- Onion Problems That Influence Variety Choice
- The Future of Onion Diversity
Introduction
Onions are not one crop in any simple sense. The word onion covers bulb onions, bunching onions, scallions, shallots, multiplier onions, sweet onions, storage onions, and regional landraces shaped by climate, day length, soil, storage needs, and cooking traditions. This article separates real onion groups from loose naming, then explains how onion diversity developed across the world without treating marketing names as separate botanical facts.
1. The Onion Story: How One Crop Spread Across the World
The onion is one of the oldest cultivated food crops still grown in modern gardens and farms, but its beginning is harder to pin down than many vegetables because the wild ancestor of the common bulb onion is not known with certainty. The common bulb onion, Allium cepa, is known from cultivation, while closely related wild species occur in parts of Central Asia and nearby regions. Several historical and botanical sources place the likely origin or early development of onion cultivation in Central Asia, Iran, or western Pakistan, but the exact domestication route remains uncertain. That uncertainty matters because it keeps the history honest. Onions were not invented as one finished vegetable. They were selected over long periods for edible bulbs, storage ability, flavor, shape, color, day-length response, and usefulness in cooked food. From that long selection came the major cultivated forms people still recognize today, including Bulb Onion, Shallot, Multiplier Onion, and later regional forms connected to local food systems. A storage onion grown for winter use is not the same kind of crop problem as a fresh green onion cut young for leaves, even when both belong to the larger onion world. That is why global onion diversity cannot be explained by color alone. Yellow, red, and white onions are only the visible surface of a much older pattern of selection.
As onions moved through farming regions, they were shaped by climate, latitude, soil, storage needs, cooking habits, and local seed selection. A farmer saving onions for long storage would favor bulbs with firm skins, lower moisture loss, and good keeping ability. A grower supplying fresh markets might favor mild flavor, large size, or tender green tops. In East Asia, long-stemmed and non-bulbing or weakly bulbing onions became important, including Welsh Onion, Japanese Negi, and related bunching onion forms. In Mediterranean regions, flat, red, mild, or specialty bulbs became important in local cuisines, including types related to Tropea Onion and Cipollini. In North America, regional sweet onions became famous where day length, soil, sulfur levels, and marketing systems allowed mild bulbs to be grown and identified by place, including Vidalia, Walla Walla, and Maui Onion. These names do not all represent the same level of botanical difference. Some are botanical groups, some are landraces, some are regional production types, and some are named cultivars. The useful way to understand onion varieties worldwide is to separate true crop types from marketing names, then look at how each type solved a real agricultural or culinary problem.
2. What Is an Onion? Understanding the Allium Family
The onion belongs to a larger botanical group called Allium, a genus containing hundreds of species that includes garlic, leeks, chives, shallots, scallions, bunching onions, and ornamental flowering onions. Although many vegetables are casually called onions in cooking, not all belong to the same species or are grown for the same purpose. The common bulb onion, Allium cepa, is the foundation for most storage, sweet, yellow, white, and red onions sold around the world. Within Allium cepa are multiple cultivated forms including dry bulb onions, bunching onions, and multiplier onions. Other onion-like crops belong to separate species entirely. Welsh Onion (Allium fistulosum) forms the basis of many bunching onions and scallions, while the leek, Allium ampeloprasum, develops a thick edible stem rather than a true bulb. Garlic, Allium sativum, occupies another branch of the same botanical family despite having cloves instead of a single bulb. These distinctions matter because vegetables grouped together in kitchens often behave differently in the field, respond differently to weather, and possess separate growth habits, pest pressures, flowering patterns, and storage qualities.
The confusion surrounding onions often comes from naming traditions rather than botany. A scallion may be harvested from a young bulb onion, but it may also come from a non-bulbing bunching onion such as Ishikura Long White Onion, which remains elongated rather than forming a round bulb. Shallots are commonly described as small onions, yet traditional shallots belong to the Aggregatum Group of Allium cepa, reproducing by clustered offsets rather than by one large bulb. Multiplier Onion, sometimes called potato onion, behaves differently again, multiplying underground through clustered bulbs that divide into groups. Japanese Negi, Wakegi, and Korean long onions developed through centuries of regional cultivation for long edible stalks, flavor balance, and cold tolerance rather than storage bulb production. Some onions are valued for sulfur-rich pungency, others for mild sweetness, and some for leaf production instead of bulbs. Even within bulb onions, differences between long-day, intermediate-day, and short-day onions strongly affect bulb formation. Understanding onion diversity begins with separating species, crop groups, and culinary naming traditions. Many vegetables sold under the broad label “onion” are related, but they do not represent one single crop type. They represent a family of cultivated plants shaped over centuries for separate agricultural purposes, regional cuisines, and storage systems.
3. The Major Onion Groups Grown Worldwide
Global onion production is not based on one universal onion but on multiple cultivated groups that developed for separate purposes. The familiar round bulb onion remains the largest category and includes dry storage onions, sweet onions, red onions, white onions, and yellow onions grown from Allium cepa. Bulb onions are selected for characteristics including storage life, bulb size, pungency, sweetness, skin thickness, and resistance to splitting or bolting. Alongside bulb onions are bunching forms that produce edible stems and leaves with limited or no bulb formation. Welsh Onion, often called bunching onion, became important across East Asia because of repeated harvest potential and strong cold tolerance. Scallions and green onions may come from harvested immature bulb onions or from bunching species that remain stem-focused throughout growth. In many regions, bunching onions became equally important to bulb onions because they fit daily cooking systems requiring repeated harvests rather than long storage.
Other onion groups developed for specific culinary or agricultural uses. Shallot and Multiplier Onion types produce clusters of bulbs rather than one enlarged bulb, making them useful in regions where vegetative reproduction offered stable production without dependence on seed. Flat onions such as Cipollini developed for roasting and cooking, while elongated forms such as Torpedo Onion became important in Mediterranean production systems. Long-stemmed onions such as Japanese Negi, Kujo Negi, and Daepa in Korea were selected for stem length, flavor, and cooking performance rather than storage. Egyptian Walking Onion, a hybridized perennial form, developed aerial bulbils at the top of stalks that fall and root nearby, giving rise to the common name “walking onion.” Pearl onions remained important for pickling and whole-cooking applications due to small bulb size, while large sweet onion groups expanded in places suited to low sulfur flavor profiles and fresh eating. Although many commercial names exist, most cultivated onions worldwide still fall into a limited number of biological and agricultural categories. Understanding those groups is more useful than memorizing hundreds of seed catalog names because crop behavior, storage, flavor, and production traits usually follow these larger historical onion divisions.
4. Why Onion Varieties Are Different: Day Length and Bulb Formation
One of the most important reasons onion varieties differ is a biological process called photoperiod response, commonly described as day-length sensitivity. Unlike many vegetables that grow mainly according to temperature, onions begin bulb formation based largely on the number of daylight hours they receive. This process determines whether an onion forms a large bulb, remains small, bolts early, or fails to develop properly. Onion breeders and seed systems therefore separate onions into long-day, intermediate-day, and short-day groups. These categories are not marketing terms but biological requirements tied to latitude. Long-day onions generally begin bulbing when daylight exceeds roughly fourteen to sixteen hours, making them suitable for northern latitudes. Short-day onions bulb under shorter daylight periods closer to ten to twelve hours and therefore became important in southern regions. Intermediate-day onions occupy a middle range and are commonly grown in transitional areas where day length does not strongly favor either extreme.
The importance of day length explains why an onion variety can perform normally in one state yet fail in another even when soil fertility, nutrients, irrigation, and temperature appear acceptable. A northern storage onion planted too far south may never form a proper bulb, while a southern sweet onion planted too far north may bulb prematurely and remain small. Famous onion groups illustrate this pattern clearly. Vidalia-type onions belong to short-day systems adapted to southern growing regions, while many northern storage onions such as Patterson, Copra, and Stuttgarter fit long-day conditions and developed reputations for storage performance rather than mild flavor. Walla Walla Onion, grown in northern regions, behaves differently than southern sweet onion systems despite being grouped loosely under sweet onions. Day length also influences onion breeding, seed production, and regional specialization because varieties must match predictable seasonal light conditions to produce usable bulbs. Temperature still matters, particularly for growth speed and bolting risk, but photoperiod largely controls whether onions begin forming bulbs at the correct stage of development. This biological requirement explains much of the global diversity seen in onions and helps separate true agricultural adaptation from simple naming differences found in seed catalogs.
5. Sweet Onions vs Storage Onions: Why Flavor Changes
Not all onions are bred or selected for the same purpose, and one of the clearest divisions in global onion production is the difference between sweet onions and storage onions. Although sweetness is often treated as a simple taste preference, the distinction comes from chemistry, moisture content, sulfur compounds, storage behavior, and regional growing conditions. Storage onions were historically important because people needed bulbs that could survive for months after harvest without rotting or sprouting. These onions generally develop firmer bulbs, tighter skins, lower water content, and stronger pungency caused by sulfur-containing compounds that help create the familiar sharp onion flavor and eye irritation during cutting. By contrast, onions classified as sweet usually contain lower pungency levels, thinner skins, and higher moisture content, making them more suitable for fresh eating but less suitable for extended storage. Sweetness in onions does not mean high sugar levels in the same way fruit sweetness works. Rather, it often reflects lower sulfur intensity, which allows natural sugars already present in the bulb to become more noticeable. This difference explains why two onions can appear similar externally while tasting entirely different in the kitchen.
The contrast between famous onion types helps explain how these categories developed. Vidalia Onion, associated with Georgia production, belongs to a short-day onion system and is known for lower pungency resulting partly from cultivar selection and growing conditions. Maui Onion in Hawaiʻi gained attention for mild flavor under local production systems, while Walla Walla Onion in Washington became associated with fresh use and milder eating qualities in northern production areas. These onions generally do not possess the long storage life associated with northern storage onions such as Patterson, Copra, or Stuttgarter, which were selected for winter keeping ability, thicker skins, and reduced spoilage during storage. A strong onion is not automatically better than a mild onion, nor is a sweet onion inherently superior. The difference reflects agricultural purpose. In regions where households historically needed bulbs to survive winter, storage performance mattered more than tenderness or sweetness. In regions with longer harvest windows or access to fresh markets, milder onions gained importance. Soil sulfur availability can also influence flavor intensity, but genetics and production type remain major factors. The result is a worldwide onion system divided not only by color or size but also by how long onions must store, how they are eaten, and what growing conditions shaped their selection over generations.
6. Onion Colors and What They Actually Mean
Onions are commonly divided into yellow, white, and red or purple groups, but color alone does not fully explain flavor, storage ability, or culinary use. The visible skin and flesh color mainly reflect pigment chemistry rather than separate species. Most cultivated onions belong to Allium cepa, whether yellow, white, or red. Yellow onions dominate commercial production in many countries because they balance storage ability, cooking versatility, and strong onion flavor. White onions are commonly associated with smoother appearance, lighter flesh, and culinary traditions that favor sharper raw use or cleaner presentation in dishes. Red or purple onions contain pigments called anthocyanins that produce coloration ranging from pinkish-purple to deep red depending on genetics and growing conditions. These pigment differences do not automatically determine sweetness or pungency, although some color groups became associated with particular culinary habits through repeated selection and regional food traditions. A white onion can be pungent, mild, sweet, or sharp depending on cultivar and growing conditions, just as a yellow onion can range from storage type to fresh-use onion. Color is therefore better understood as a category of appearance rather than proof of flavor or performance.
The relationship between color and use becomes clearer when specific onion groups are examined. Many long-storage onions such as Copra, Patterson, and Stuttgarter belong to yellow storage traditions because bronze or yellow skins protect bulbs well during curing and storage. Red onions such as Red Burgundy became popular for fresh slicing, salads, and visible color contrast in food, although red onions are also cooked and stored in many production systems. White onions became important in culinary regions emphasizing roasting, sauces, Mexican cooking traditions, or mild slicing uses. Regional heirloom onions show even greater diversity. The flattened red Tropea Onion of Italy differs visually and chemically from northern storage onions, while sweet onion groups such as Maui Onion or Vidalia-type onions may be yellow despite being known more for mildness than storage life. Onion color can sometimes suggest probable use, but it does not reliably predict flavor strength, sulfur content, sweetness, or storage performance on its own. Genetics, day-length adaptation, water content, curing quality, and sulfur chemistry influence flavor more directly than skin color. For that reason, experienced onion production systems classify onions by growth habit, storage behavior, and regional adaptation before using color as a meaningful category. Color matters, but it is only one visible part of a much larger agricultural story.
7. Onion Varieties by Region of the World
Onion diversity developed differently around the world because regions selected onions according to climate, storage needs, cooking systems, and available growing seasons. East Asia favored long-stemmed onions and bunching forms that could be harvested repeatedly or incorporated into soups, stir-fries, grilled foods, and broths. Japanese Negi, Kujo Negi, and Ishikura Long White Onion developed for long edible shafts rather than large storage bulbs, while Korean production systems expanded large green onions such as Daepa for kimchi, soups, and cooked dishes. China maintained extensive scallion and bunching onion traditions connected to repeated harvest systems and regional cuisine. In Mediterranean regions, onions often developed distinctive shapes, sweetness levels, and culinary identities linked to local agriculture. Italy produced flattened, elongated, and mild regional onions including Tropea Onion, Borettana Onion, and Cipollini forms used in roasting, braising, and preservation. Central Asia and the Middle East remained important historically because these regions are often connected to early onion domestication and long-term cultivation history.
North America developed onion systems shaped heavily by latitude and day length. Northern regions favored long-day onions capable of winter storage, while southern production favored short-day sweet onions harvested fresh. Vidalia Onion became associated with Georgia production, Walla Walla Onion developed in Washington State, and Maui Onion gained recognition in Hawaiʻi under island growing conditions. Europe retained many historic landraces selected for local storage and flavor needs, while India developed extensive red onion systems suited to storage and transport under high production volumes. In some countries, onions became strongly associated with trade and regional identity rather than purely botanical distinction. A named onion may represent a stable cultivar, a regional production type, a landrace, or simply a geographic designation tied to growing conditions. The result is that onion diversity across the world reflects centuries of adaptation rather than random naming. Regions repeatedly selected onions that solved local agricultural problems involving storage, seasonal timing, cooking methods, flavor preferences, and environmental conditions. Understanding onion geography therefore helps explain why global onion varieties differ so widely in shape, flavor, pungency, storage life, and growth habit even when many still belong to the same cultivated species.
8. Famous Onion Varieties and Why They Matter
A small number of onion varieties and regional onion types became widely recognized because they represent important agricultural systems, unusual physical traits, or historical production patterns rather than simple marketing success. Some onions became known for storage ability, others for sweetness, bulb size, or regional adaptation. Vidalia Onion, associated with Georgia, became recognized for mild flavor linked to short-day production systems and local growing conditions. Walla Walla Onion developed importance in the Pacific Northwest and became associated with fresh use and relatively mild flavor. Maui Onion, grown under Hawaiian production conditions, gained recognition for sweetness and fresh eating uses. Storage onions such as Copra, Patterson, and Stuttgarter matter for different reasons because they were selected for keeping quality, curing performance, and reduced storage loss over winter. In Europe, regional onions such as Tropea Onion and Cipollini became connected to distinct culinary traditions and recognizable shapes rather than long storage.
Asian onion systems produced equally important varieties that are less familiar in North America but highly significant within regional cuisines. Ishikura Long White Onion developed as a bunching onion valued for long white shafts and limited bulbing, while Kujo Negi and other Japanese long onions became important for repeated harvest and cooking use. Welsh Onion, despite the name, is not from Wales but refers to Allium fistulosum, a major bunching onion species used across Asia and colder climates. Egyptian Walking Onion became notable for forming bulbils at the top of flowering stalks that eventually bend and root nearby, producing a spreading perennial habit uncommon among onions. Some onions matter because they demonstrate how regional agriculture solved practical problems. A long-storage onion reflects historical food security, while a bunching onion reflects repeated harvest systems and fresh cooking traditions. Famous onions therefore deserve attention not because they are automatically superior, but because they represent stable agricultural responses to climate, season length, cooking practices, storage demands, and regional selection over long periods of cultivation.
9. Why There Are Hundreds of Onion Varieties Worldwide
The large number of onion varieties found around the world developed through a combination of geography, storage requirements, climate adaptation, culinary preference, and centuries of repeated seed selection rather than through random naming alone. Unlike vegetables that can be moved easily across climates with limited adjustment, onions respond strongly to day length, temperature, and seasonal timing. This biological sensitivity encouraged regional selection systems where farmers repeatedly saved seed from onions that performed best under local conditions. Over time, stable onion populations developed that differed in bulb shape, pungency, storage ability, skin thickness, maturity timing, and resistance to splitting or premature flowering. In northern climates, long-day onions capable of surviving winter storage became important because households historically depended on preserved food supplies. In warmer regions, short-day onions developed around mild flavor and faster production systems suited to local growing seasons. East Asian agriculture selected heavily for stem production and bunching habit rather than bulb size, producing onions such as Japanese Negi, Kujo Negi, and forms related to Welsh Onion. Mediterranean agriculture encouraged flatter onions, roasting onions, sweet onions, and elongated bulb forms linked to local cuisines and preservation practices. These repeated agricultural pressures created real biological diversity long before modern seed companies existed.
The number of onion names becomes confusing because not every named onion represents the same level of difference. Some onions are true cultivars stabilized through breeding, while others are regional landraces shaped over centuries of local seed saving. A landrace onion may contain genetic variation while still remaining recognizable as a stable regional type. Tropea Onion, Walla Walla Onion, Maui Onion, and Vidalia-type onions each reflect regional production histories, but they are not equivalent categories biologically. Some names represent legally protected production regions, others refer to open-pollinated cultivars, and others describe families of onions with similar traits rather than one exact genetic line. Modern breeding added another layer by producing hybrids selected for storage, disease resistance, uniformity, shipping ability, or mechanical harvest. Seed catalogs further expanded naming systems by introducing breeder codes, trademarks, and regional marketing labels that sometimes make the number of onions appear larger than it really is. Yet beneath those commercial layers, genuine onion diversity remains extensive. Hundreds of onions exist because agriculture repeatedly solved different problems: surviving winter, storing food, producing mild flavor, tolerating short seasons, resisting bolting, fitting regional cuisine, or growing successfully under different daylight patterns. The result is not marketing inflation alone but a crop shaped repeatedly by biology, geography, and human food systems over long periods of cultivation history.
10. How to Choose the Right Onion Variety for Garden and Kitchen Use
Choosing an onion variety begins with understanding biological compatibility rather than flavor alone because onions respond strongly to latitude and day length. An onion that performs normally in one region may fail entirely in another if the daylight requirement does not match local conditions. Long-day onions generally suit northern latitudes where summer daylight exceeds fourteen hours, while short-day onions develop more successfully in southern regions with shorter winter and spring daylight periods. Intermediate-day onions occupy a middle zone and may adapt across transitional growing regions. Before differences in sweetness, pungency, color, or culinary use matter, an onion must first be capable of producing a proper bulb under local light conditions. Storage expectations also matter because onions bred for fresh eating often possess thinner skins and shorter shelf life than onions selected for curing and winter storage. Shape, maturity timing, bolting tendency, sulfur intensity, and disease performance also vary between cultivars. A strong storage onion and a mild slicing onion represent different agricultural purposes even when both belong to Allium cepa.
After biological fit is established, onion selection becomes more practical and connected to use. Patterson, Copra, and Stuttgarter represent storage-oriented onion systems valued for curing and winter keeping ability, while onions such as Vidalia-type onions, Walla Walla Onion, and Maui Onion are associated more closely with fresh use and lower pungency. Flat onions such as Cipollini behave differently in cooking than elongated onions such as Torpedo Onion, and bunching onions such as Ishikura Long White Onion or Welsh Onion serve purposes entirely different from storage bulb onions because edible stems rather than mature bulbs become the main harvest. Culinary traditions also shape onion use. Some regions rely on strong onions for roasting, soups, braising, or long cooking, while others favor milder onions for slicing or fresh dishes. Onion color can influence appearance in food but does not reliably predict flavor strength or sweetness. Storage length, bulb size, cooking method, sulfur intensity, and regional adaptation often matter more than color alone. The useful approach is to match onion type to biological compatibility and intended food use rather than assuming one onion category serves every purpose equally well.
11. Onion Problems That Influence Variety Choice
Not all onion problems affect every variety equally, and many of the most common production failures are linked to genetics, day length, storage behavior, and environmental response rather than simple mistakes in growing. Bolting, which occurs when onions send up a flowering stalk too early, represents one of the most important problems because once flowering begins the bulb often loses storage quality and becomes less useful for normal culinary use. Premature bolting may be triggered by temperature exposure, variety sensitivity, or mismatched planting timing. Storage failure also differs among onion groups. Sweet onions and high-moisture onions frequently spoil sooner than dense storage onions because thinner skins and greater water content reduce long-term keeping ability. Diseases including neck rot, basal rot, downy mildew, bacterial soft rot, and pink root can affect onions, but susceptibility varies between cultivars and production environments. Pest pressure also influences outcomes. Onion thrips, one of the most recognized onion pests worldwide, damage foliage by feeding on leaves and reducing plant vigor, while onion maggots attack belowground tissues and developing bulbs. Regional climate, field sanitation, crop rotation, and cultivar selection all influence how severe these problems become. The same onion variety may perform differently under separate environmental conditions even when managed similarly.
The effect of these problems becomes clearer when comparing onion types. Long-storage onions such as Patterson, Copra, and Stuttgarter were historically selected in part because they handled curing and storage better than softer onions intended for quick use. Mild onions such as Vidalia-type onions or Maui Onion may possess desirable eating qualities but generally do not maintain storage quality for the same length of time as stronger storage onions. Day-length mismatch creates another major issue because onions planted outside their suitable latitude may bulb poorly, remain undersized, or mature unpredictably regardless of nutrients or irrigation. Bunching onions such as Ishikura Long White Onion, Welsh Onion, and related scallion systems face different priorities because stem production often matters more than mature bulb storage. Some onions show stronger tolerance to cold or overwintering, while others mature quickly for fresh harvest systems. Even sulfur intensity may influence disease and storage indirectly because onion chemistry differs between cultivars. Variety choice therefore becomes tied not only to flavor or appearance but also to how onions respond to biological stress, storage conditions, flowering risk, pests, and environmental pressure. Onion problems are rarely random. Many are connected directly to selecting an onion type suited to the conditions under which it developed.
12. The Future of Onion Diversity
The future of onion diversity depends on how well traditional regional onions, heirloom populations, and locally adapted seed lines survive alongside modern breeding systems focused on uniformity, shipping, and large-scale production. Commercial onion breeding increasingly emphasizes disease resistance, storage performance, predictable maturity, bulb uniformity, mechanical harvest compatibility, and market appearance. These goals support commercial production but may also reduce emphasis on older local onions that developed for regional cooking traditions, climate adaptation, or household storage systems. Across many countries, older onion populations have already declined as farms moved toward standardized cultivars selected for large-scale agriculture. Yet local onion diversity remains important because onions adapted over centuries to different soils, day lengths, temperatures, disease pressures, and culinary systems. Regional onions such as Tropea Onion, Walla Walla Onion, Maui Onion, and many local Japanese and Mediterranean onions continue to persist partly because communities maintained them through seed saving, regional production, and culinary demand rather than abandoning them entirely.
At the same time, onion diversity continues to expand rather than disappear completely because breeders and seed systems still respond to changing agricultural problems. Climate shifts, water limitations, new disease pressures, storage concerns, and altered seasonal timing all influence onion breeding goals. In East Asia, long-stemmed onions including Japanese Negi, Kujo Negi, and related bunching onions continue to evolve through local production and culinary use. Storage onions such as Patterson, Copra, and improved long-day cultivars remain important wherever winter keeping quality matters. Short-day onion systems continue adapting to southern production regions, while intermediate-day onions help bridge areas with mixed seasonal patterns. Some onions are preserved through public seed collections, university programs, regional farming traditions, and heirloom seed networks that maintain historically important cultivars. Onion diversity therefore remains active rather than frozen in history. The large number of onion types found globally reflects continuing adaptation to human food systems, environmental change, and regional agriculture. Even though many onions belong to the same cultivated species, the future will likely continue producing distinct onion forms because the agricultural problems onions solve remain different from one place to another.
Conclusion
The large number of onion varieties found worldwide did not develop through random naming or modern marketing alone. Onion diversity emerged because different regions repeatedly selected onions that solved specific agricultural and culinary problems involving storage, climate, season length, day length, flavor, stem production, and local food systems. From Welsh Onion and Japanese Negi to Vidalia Onion, Tropea Onion, Maui Onion, and long-storage onions such as Patterson or Stuttgarter, onion history reflects adaptation over centuries. Understanding onion diversity becomes easier when onions are grouped by biology, agricultural function, and regional development rather than by color, popularity, or seed catalog naming alone.
- University of Minnesota Extension — Growing Onions in Home Gardens
https://extension.umn.edu/vegetables/growing-onions-home-gardens - Texas A&M AgriLife Extension — Onion Gardening
https://agrilifeextension.tamu.edu/library/gardening/onions/ - University of Nebraska Extension — Onions: Long Day, Short Day or Neutral?
https://lancaster.unl.edu/onions-long-day-short-day-or-neutral/ - Iowa State University Extension — What Is a Long-Day Type Onion Variety?
https://yardandgarden.extension.iastate.edu/faq/what-long-day-type-onion-variety - Illinois Extension — Onion (Allium cepa)
https://extension.illinois.edu/gardening/onion - North Carolina State Extension — Bulb Onions
https://content.ces.ncsu.edu/bulb-onions - Penn State Extension — Onion Production
https://extension.psu.edu/onion-production - Oregon State University — Types of Onions and Varieties
https://agsci.oregonstate.edu/mes/sustainable-onion-production/types-onions-and-varieties - University of Florida IFAS Extension — Understanding Short-Day vs. Long-Day Onions
https://nwdistrict.ifas.ufl.edu/phag/2024/07/26/understanding-short-day-vs-long-day-onions/ - USDA National Agricultural Library — U.S. Onion Statistics
https://esmis.nal.usda.gov/publication/us-onion-statistics - USDA Agricultural Marketing Service — Onion for Processing Grades and Standards
https://www.ams.usda.gov/grades-standards/onion-processing-grades-and-standards - USDA Agricultural Research Service — Onion Production
https://www.ars.usda.gov/northeast-area/geneva-ny/plant-genetic-resources-unit-pgru/docs/onion-production/ - North Carolina State University Plant Toolbox — Allium cepa (Bulb Onion)
https://plants.ces.ncsu.edu/plants/allium-cepa/ - University of California IPM — Onion and Garlic Pest Management Guidelines
https://ipm.ucanr.edu/agriculture/onion-and-garlic/ - University of Minnesota Extension — Onion Thrips
https://extension.umn.edu/yard-and-garden-insects/onion-thrips
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