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Growing the Allium (Onion) Family

Posted by kate.ryan | August 25, 2015

Allium is the botanical name for a group of bulbous plants that include lovely flowering perennials as well as every cook’s staple, the indispensable onion. Alliums are a genus of plants of the Alliaceae family. They have fleshy layers wrapped around and protecting a growing bulbous center filled with reserve food products. Found in the wild throughout the Northern Hemisphere, alliums sport a single naked stem (without leaves) atop which bursts an umbel. The bulb structure of alliums enables the plants to tide over during cold or dry periods safely buried in the earth until favorable conditions return.

A cool season crop, these perennials are grown by the home gardener as annuals and bloom in the spring and summer in a range of colors from whites and pinks to reds and blues and even shades of yellow. Alliums produce chemical compounds including allicin which has anti-microbial activity, steroids, oligopeptides, and fatty acid derivatives. The chemical responsible for alliums seductive taste is cysteine sulfoxide. Depending on the species of allium, the taste may be stronger or weaker and in most cases, both the leaves and the bulbs are edible. Incidentally, green onions, sometimes called scallions, are just immature bulbing onions harvested early. If left in the ground, they would develop into regular onions.

Maritime NW Favorite Variety list

This list of onion family variety favorites for Maritime NW was gathered from the suggestions and experiences of our Snohomish County Growing Groceries and Master Gardener volunteers.

Planting

Onions are heavy feeders, requiring 2 to 3 pounds of 8-8-8 fertilizer per 100 feet of row. To keep a balance in your soil, many suggest a companion planting of leeks with peas, which produce a lot of nitrogen.

Here is a planting guide for the allium groups and integrated pest management tips:

Onions – Cepa group: Plant in the spring or fall from seed, seedling or sets (small bulb). Onion varieties require different daylight hours to form a bulb. After about six months, tops of dry onions will start to turn yellow. Break the plant over and let dry for a few days. Store in a dry, dark place.

Leeks – Porrum group: Plant seeds in late summer and thin to 4-6 inches. When plants are almost full grown, push soil up around stems to blanch them white. Harvest next year in early summer before the soil gets hot. Garlic – Plant cloves (garlic does not set fertile seed) in the late summer. Next summer, cease watering and the foliage will yellow. Break over like onions. Dig up bulbs and sun dry them for about three weeks until the skins become papery.

Shallots – Aggregatum group: Plant bulbs (reproduces only by bulb) in spring. The harvest will be next summer. Dig the bulbs out when tops begin to dry. Alliums are susceptible to stem and bulb nematodes. Rotate crops and use only certified seed. These cultural practices are your best defense. Alliums are also susceptible to thrips (use insecticidal soap), maggots (destroy crop), downy mildew (keep soil well drained and allow plants to dry out between waterings) and white rot (caused by fungus – destroy crop).

Washington State University