By Mary H. Dyer, Credentialed Garden Writer
Egyptian walking onions are known by several names, including top-set onions and tree onions. Need more walking onion information? You can learn more about this interesting, attractive plant by clicking on the article that follows.
Tree onion, topsetting onions, walking onions, or Egyptian onions, Allium × proliferum, are similar to common onions (A. cepa), but with a cluster of bulblets where a normal onion would have flowers. Genomic evidence has conclusively shown that they are a hybrid of the common onion and the Welsh onion (A. fistulosum).  However, some sources may still treat the tree onion as A. cepa var. proliferum or A. cepa Proliferum Group. Tree onion bulblets will sprout and grow while still on the original stalk. They may bend down under the weight of the new growth and take root some distance from the parent plant, giving rise to the name "walking onion." It has been postulated that the name "Egyptian onion" derived from Romani people  bringing tree onions to Europe from the Indian subcontinent.
The tree onion is a species of perennial onion. It is a diploid hybrid between the bunching onion and the shallot.   Also known as turfed stone leek, it may be cultivated commercially and for foliage.   It is described as a shallot which can be grown in tropical conditions. 
The phenomenon of forming bulblets instead of flowers is also seen in garlic and other alliums, which sometimes may also be referred to as top onions or tree onions. The bulblets are usually marble-sized, between 0.5 cm to 3 cm in diameter.
Many tree onions are very strong flavoured, although some cultivars are relatively mild and sweet.  The underground bulbs are particularly tough-skinned and pungent,  and can be quite elongate, like leeks,  or in some types may form bulbs up to 5 cm across.  Young plants may be used as scallions in the spring, and the bulblets may be used in cooking similarly to regular onions, or preserved by pickling. 
Storing onions by freezing is an excellent way to preserve them. How long do red onions last if you don’t freeze them? Onions of all types last for different amounts of time depending on your storage method. In the freezer, they last for several months.
Before you start chopping onions to freeze, you need to know that frozen onions don’t work in all dishes. Once you freeze onions, they lose some of their crunchiness. If you are using frozen onions to replace fresh onions, use them in cooked dishes, including stews, soups, chilis, or any recipe that calls for sautéed onions.
Asking if you can freeze onions is almost as popular as asking, can shredded cheese be frozen? What about block cheese? Can I freeze cream cheese? The answer to all of these questions is yes.
Freezing is ideal for onion storage, provided you have enough space. The process to freeze onions is relatively easy and only requires a few minutes of your time.
When freezing your onions, do not use ordinary zip lock bags, such as sandwich bags. Use a heavy-duty freezer bag to help preserve the quality of the onion.Freezer bags also minimize odors inside your freezer.
If onion odors bother you, consider storing your onions in a separate freezer. For the best flavor and quality, use up frozen onions within six months. If frozen onions clump together, hit the bag against the counter a few times to break up the clumps.
If you are ready to start freezing your excess onions, all you need to do is follow a few simple steps. You can use large freezer bags, but we recommend using smaller bags, so you are only thawing as much as you need each time just as when you are freezing beans.
Begin by peeling your onions. Use a knife or food processor to dice, slice, or chop onions. You can cut your onions in various ways, so you have different sized pieces on hand for a variety of recipes. Add diced onions to freezer bags and then push out as much air as you can before sealing the bag closed.
Write the portion amount and the freezing date on the baggies with a permanent marker. The portion amount allows you to pull out only as much as you need from the freezer, as you cannot refreeze onions. The date ensures you use the oldest ones first to preserve taste.
Freeze the onions by laying them flat on a cookie sheet and then putting them inside a freezer. Freezing the bags flat allows you to stack them inside for easier storing. Once onions are entirely frozen usually, a couple of hours, remove bags from cookie sheets and place directly inside the freezer.
If you are wondering can you freeze green onions, the answer is yes. The downfall of freezing green onions is they do not retain their crispness, but they still offer plenty of flavor. When green onions freeze, they become tougher upon thawing. The freezing process for green onions is the same as for diced or chopped onions.
Begin by peeling, trimming, and cleaning the green onions. Chop or dice the green onions into ¼ inch pieces. Blanching is not required. Package cut onions in freezer containers or bags and leave about ½-inch of headspace.
Remove as much air as you can. Another way to freeze diced green onions is by laying out the cut onions in a single layer, so each piece freezes separately. Once frozen, after several hours, scoop into various containers and store in the freezer for up to six months.
Caramelized onions are one of the best kinds of onion to freeze the best part is that freezing doesn’t affect their flavor at all, and you can make them in the crockpot or on the stove. Caramelized onions offer a sweet and nutty flavor that makes a great addition to many dishes.
Still, the process of caramelizing the onions takes longer than most people want to spend on a busy weeknight. When caramelizing onions, the volume decreases a lot, so always make a bigger batch than you think you need.
When caramelized, four large onions only make about two cups, so the more you cook, the better. Like other onions, you can store caramelized ones in the freezer for up to six months. Just watch for signs of freezer burn.
You can freeze caramelized onions in three different ways. The first method is to pack them into ice cube trays, which is perfect for when you need smaller portions. The second way is to use muffin tins, but line the tin with plastic wrap to make removing the frozen onions easier.
The third option is to use freezer bags. You will also need to transfer the frozen onions from ice cube trays or muffin tins into freezer bags for long term storage. If freezing directly in a freezer bag, always freeze them in a thin layer, nothing more than ½-inch thick. To use, break off as big or small of a section as you need.
Sometimes onions begin sprouting and going soft before we can use them. Rather than just tossing the onion, you can still freeze it, but not the same way you can with fresh onions.