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HOME / FACTSHEETS / VEGETABLES / VEGETABLE CROP GUIDES / ONIONS PRODUCTION GUIDE /

Onion Introduction

The common dry yellow onion belongs to the Amaryllidaceae (Amaryllis family). Allium Cepa is related to a great number of other species of similar odor and taste -- garlic, leek, chive, welsh onion. The shallot is considered a form of A. cepa. Asia is considered the centre of origin -- Northwestern India, Afghanistan, parts of the USSR and China. The onion has been known and cultivated from the earliest period of history (for at least 5000 years). Onion culture spread into Northern Europe in the Middle Ages.

Onions are a cool season crop. The germination of onions is slow at 6 to 7º, the optimum germination temperature range is 10 to 35º, and the maximum temperature is 40º. The onion crop is adapted to a growing season with air temperatures at 13 to 24º. Low temperatures early in the season are desirable with higher temperatures after bulb formation. The onion is tolerant of frost but seedlings are generally only tolerant down to -1º. Some bunching onion cultivars overwinter in the milder areas of Atlantic Canada. Adequate soil moisture is required due to the relatively small root system.

Onions are sensitive to photoperiod. Long days are favorable to onion production as this enhances leaf development and formation which, in turn, is directly related to bulb size. Early varieties require 13 hours for bulb initiation while late varieties require 16 hours for bulb initiation.

Onions begin to form bulbs when day length reaches the appropriate duration for the cultivar, providing temperatures are high enough. Early seeding or transplanting is therefore essential. Cool weather during early growth of the plant promotes formation of seed stalks (bolting). The onion bulbs quicker in warm than at cool temperatures. At 40º bulbing is retarded. In the onion there is an interaction between day length and temperature in the bulbing process of an individual cultivar.

Onion soils should be well drained and well supplied with organic matter. Sandy loams and loams without stones are optimal. Heavy clay soils should be avoided. Coarse sand soils may be used for specialty onion production under irrigation.

Early onions are grown from sets sown in mid to late April. These stands mature in late August and early September and are marketed. Usually these are "Jet Set".

Onions from seed do not usually mature until mid to late September. (Onions started from transplants mature about the same time as sets.)

Bunching onions may be planted in early August and overwintered. Bunching onions also may be planted in the spring for harvest in late July and August. It is possible tunnel houses could be used to extend the season on bunching onions. Large Spanish onions are usually grown from transplants as they take a long time to mature. Spanish type onions can be direct seeded if only a 7 to 8 cm diameter onion is required for processing. Yellow onion yields range from 18,000 to 40,000 kg per hectare. Green bunching onions yield 20,000 to 24,000 kg per hectare.

There are relatively large markets for yellow onions (including Spanish) for both fresh and processing in the Atlantic Area. There are export markets to the Caribbean that are being developed. Onions of all types could be grown for roadside market sales and for speciality items for the Hotel, Restaurant & Institutional Trade.

Nutrient Content: One medium raw onion supplies 40 kilocalories. It contains Vitamin C, potassium and calcium plus trace amounts of other nutrients.