Are you an onion addict who dreams of a steady supply of fresh Allium? Expanding your onion repertoire with perennial onions is your best bet. Egyptian walking onions (Allium x proliferum), also called tree onion or topset onion, is a three-in-one perennial onion that can be harvested from spring to fall in Zones 5 to 9.
Why Grow Walking Onions
Perennial vegetable gardeners are spoiled for choice when it comes to perennial onions. Still, Egyptian walking onions stand out from the bunch by growing tiny bulbs called “bulblets” on the tops of their stems instead of flowers. Without harvesting, these bulblets get heavy enough to tip the stem over into the soil and start a bunch of new plants. In essence, they “walk” to a new spot in your garden, so you end up with an abundance of plants.
If you’re familiar with binomial names for plants, you know that the “x” in a name denotes a hybrid. Allium x proliferum (Egyptian walking onion) is a hybrid of the common onion, Allium cepa, and the Welsh onion, Allium fistulosum. Due to its hybrid nature, walking onions possess traits from both parents: the mild green stems of Welsh onions and the juicy, rounded bulbs of the common onion.
Unlike the usual annual onion gardeners grow, topset onions can be harvested during the entire growing season. Annual onions need to be babied until they’re harvested in late summer to fall, and often end up sprouting or rotting before the next planting. If you’re looking for onion self-sufficiency, Egyptian walking onions are the way to go.
How to Grow Topset Onions
Topset onions grow so profusely that the better advice might be on how to control topset onions. After establishing one plant, you can quickly end up with a large area overrun by walking onions. It’s important to select a good spot for your perennial onion bed because they’ll grow back in the same spot year after year. You can also grow in containers if you’re worried about controlling them.
Ideally, tree onions need full sun, but they can grow in light shade. Like all onions, they need light, well-drained, rich soil. As is the case with all perennial crops, a good layer of mulch keeps weeds away and helps protect the bulbs and roots during winter months.
To plant, simply set bulbs or bulblets in the soil 2 inches deep and water well until established. The spacing is dependent on how large you want your underground bulbs to be and how thick you would like your green stalks. For big bulbs plant about 8 inches apart. For an abundance of chive-like green stalks, plant about 3 inches apart. You will find that each bulblet you place in the soil will multiply into a clump of multiple plants with multiple bulbs.
You can plant in either spring or in late summer to fall (before the first frost), depending on when you want your first harvest. Topset onions grow fast, so you can harvest them sooner than other perennial vegetables. It takes between 65 to 80 days for the underground bulbs to mature, so planting in fall means you can harvest the underground bulbs earlier during the next growing season.
How to Harvest Tree Onions
There are three stages to harvesting tree onions: 1) the green stems, 2) the topset bulbs and 3) the underground bulbs. To get the most out of your growing season you should have many different plants that can be harvested at different times.
Tree onions are one of the first plants to emerge in spring. If you planted in fall, you can harvest the green onions starting in the spring when the tops grow to about 8 inches tall. Simply loosen the soil around and under the bulbs and pull the plant out.
Alternatively, if you don’t have a lot of plants you can simply cut parts of the stems off as needed and let them regrow so you can harvest the bulbs later. Harvesting too much from the stems will make the underground bulbs grow slower. Also try to keep some stems with topsets on them so you can harvest the bulbils later on.
Around early summer the stems will start producing clumps of bulblets (also called bulbils or offsets) at the top of the stem. These can be harvested at any time, though for ease of peeling and slicing they should be harvested when they’re 1 or more inches in diameter (think a pearl onion or shallot). Save any extra bulblets to plant in fall (or earlier, if you want more green onions).
The underground bulb portion can be dug up at any time during the growing season. You can wait until the end of the growing season (if planted the previous fall) or a year later, in spring (if planted in spring) for large, round bulbs. You’ll know when the bulb is fully mature when the leaves turn wilted and brown, similar to when you would harvest common onions. Alternatively, you could harvest them a few months after sprouting for a milder leek substitute. The bulbs never get as large as the common onion because they tend to multiply into smaller bulbs or put most of their energy into producing topsets.
Walking Onion Maintenance
There’s very little to be done in terms of maintenance for Egyptian walking onions. It’s an incredibly tough plant that is happy to grow and spread indefinitely.
The main concern is to keep the soil lightly moist, but not soggy or waterlogged. A moderate to heavy rain once or twice a week should be enough if the plants are growing outside and well-mulched, but you may want to water after a few days to a week of hot weather and severe drought. If you’re growing topset onions in containers, check the soil daily to make sure they haven’t dried out, as soils tend to lose water faster in containers.
Another maintenance consideration is how readily the plants spread if left to their own devices. Try to harvest the topset bulbs before they get too heavy and fall over, or you’ll miss the bulblet harvest and end up with another plant where you might not want or need one. You may also need to pull up plants that are growing outside of the area you set aside, since the stems can flop over many inches away from the center of the plant.
Lastly, for large bulbs you’ll need to divide the plants every two to three years so that you don’t end up with lots of tiny bulbs and overly thin stems. The process is the same as when you divide Narcissus or other perennial bulbs in the garden to keep them robust. Luckily you can eat whatever you don’t replant so nothing is thrown away.
Honestly, you could probably disregard all the growing and maintenance tips in the article, toss a few bulbils on a patch of soil in the garden or in a large container, forget about it and still end up a with a generous harvest of Egyptian walking onions. That’s how easy they are to grow!
Other Perennial Vegetables
Here is an article that discusses several other perennial vegetables, 10 Perennial Vegetables for Colder Climates.
Cooking Egyptian Onions
There are a lot of different ways you can use your harvest, since onions abound in cuisines from all around the world. You might need to modify recipes slightly, since they are stronger tasting than anything you can get at the grocery store. Even if you decide to try out loads of onion-based recipes, it’s unlikely you’ll ever run out!
Here are some recipes that specifically require walking onions:
Written by: Marika Li