Differences exist between multiplier onions that can cause confusion for gardeners. One good way to think about them is to say, "All top-setting onions are multipliers, but not all multipliers are top-setting." Many different colloquial common names for these onions can also be a source of confusion. Here are descriptions and details for our different multiplier onion types:
Potato or Multiplier Onions
- Allium cepa v. aggregatum
- Potato onions are a form of shallots that can grow into large onions in one season if they are planted in the fall or very early spring.
- If these onions are left in the ground, they will then sprout to form a cluster of underground small bulbs to be used the following year. These shallots can be used for dry onions with some selected for replanting.
- Harvest is dependent on when they were planted of course, but early spring plantings can be harvested as single bulbs in July or Aug. typically. If you are planning on harvesting them as green onions, they can be harvested from spring to summer.
- Once established in your garden, multiplier onions will improve in size and quality as plants mature, and their bulbs can be replanted year after year.
- For green onions, plant bulbs 1-2 inches apart, and 1-1.5 inches deep.
- If they are to be harvested primarily for bulb onions space them at 4-6 inches apart.
Walking Onions, (Egyptian Walking onions), Tree Onions, or Top-setting Onions
- Allium cepa v. proliferum
These are all common names used to reverence the same type of heirloom onions.
All are very hardy, perennial plants but they are all man-made hybrids with only garden provenance to identify and date their existence or origination of them. But they have been cultivated in N. America and Europe for over 200 years.
NOTE: Since they did not originate in Egypt, this common name is falling out of favor due to no credence for the place name.
- These onions typically form several small bulbs underground, but their distinguishing habit is that they produce clusters of reddish-colored, hazelnut-sized bulbils at the top of each seed stalk, with no normal flowers forming.
- As the bulbils mature and gain size, if they are not removed, their weight causes the scape to bend down to the ground away from the mother plant where the bulbils can eventually root in and grow into another plant. This is how they were said to "walk" from place to place.
- Walking onions are often utilized as a productive form of scallions, but some top-set bulbils can grow to the size of pearl onions.
- Although the bulbils can be prized for pickling, most people harvest the bulbils for replanting in the fall.
- In the fall bulbs should be spaced 6-10 inches apart and planted about 1.5 inches deep in organically rich, well-drained soil with good moisture.
- When new shoots appear in spring those may be harvested and used as chives, or green onions, otherwise, wait until top sets form later in summer to use those, or dig an entire clump and harvest the underground bulbs.
Any way you choose to use them, walking onions are some of the easiest onions to grow and are great for kids and novice gardeners to start with.