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I have not grown that plant though from what I have read some folks keep the blooming stalk pinched off. At least that is what we do to keep onions producing longer.
Some plants that are said to be perennial are actually biennial plants which means that the plant only lives two years.
There is also a lot of factors that come into play such as where a person lives, soil,
water, etc.
Walking onions are called perennial though my observation have proven that they are biennial.