Green onions, often used interchangeably with scallions or spring onions, can return year after year, depending on the variety planted. The types that reliably regrow are bunching onions, which are true perennials that survive winter and resume growth in spring. These plants offer a continuous supply of fresh greens, unlike common bulbing onions harvested when young. Understanding the biology and employing correct harvesting methods allows gardeners to maintain a perpetual patch.
Distinguishing Perennial Green Onions
Confusion about whether green onions are perennial stems from their interchangeable naming. The true perennial variety belongs to the species Allium fistulosum, commonly called bunching onions, Welsh onions, or Japanese bunching onions. Unlike common onions (Allium cepa) harvested early as scallions, bunching onions do not form a large, terminal bulb.
The Allium fistulosum variety is non-bulbing, grown specifically for its long, straight, white base and hollow green leaves. This characteristic allows the plant to focus energy on leaf production and multiplication. If a bulbing onion is harvested young, that plant will not return. A true perennial bunching onion is programmed to survive dormancy and regrow.
Understanding How They Regrow
The perennial nature of bunching onions is rooted in their subterranean structure, allowing them to survive cold periods and regenerate. The plant maintains a small root base that remains viable in the soil throughout winter. This root structure stores energy reserves to initiate new shoots once warmer temperatures return.
These onions multiply primarily through vegetative reproduction, known as tillering or division. The original plant produces offsets, or side shoots, from its base, forming new individual plants in dense clumps. Each new shoot develops its own root system and leaves, increasing the size and density of the patch over time. This continuous natural division makes them a reliable, long-term crop.
Harvesting for Continuous Yield
To ensure a continuous supply, the “cut-and-come-again” harvesting method must be used. This technique involves taking only the leaves and upper stem while leaving the plant’s root base and growth point intact. Harvesting the entire plant by pulling it from the ground will kill it.
The correct procedure involves using a sharp knife or scissors to snip the hollow green leaves about one inch above the soil line. Leaving this small portion of the white stem and the attached root system allows the plant to photosynthesize and quickly generate new foliage. Harvesting only the outer leaves from a clump keeps the central growing point undisturbed, promoting rapid regrowth, often producing a new flush in a week or two.
Long-Term Care and Dividing Clumps
For perennial green onions to remain productive and vigorous, they require periodic maintenance beyond simple harvesting.
Winter Protection
In colder climates, applying a thick layer of organic mulch in the fall protects the root crowns from severe winter freezes. Removing this mulch in early spring encourages new shoots to emerge quickly.
Dividing Overcrowded Clumps
The necessity of dividing clumps increases as the plants multiply and become overcrowded. Dense clustering leads to smaller, less vigorous stalks due to competition for nutrients and water. Dividing the plants every two to three years revitalizes the patch. This involves digging up the entire clump and gently separating the individual starts. Replant these separated plants a few inches apart in new locations to expand the perennial patch.
Fertilization
Regular applications of a balanced liquid fertilizer, such as a fish emulsion, every few weeks support the continuous leaf production demanded by frequent harvesting.