I have been interested in trying potato onions (also called multiplier onions, hill onions, mother onions, pregnant onions) and finally on impulse included some with my springtime seed order from Southern Exposure Seed Exchange. These got shipped in the Fall and my order arrived last week, a bit early for planting here but in time to prompt me to start my planning. They keep well (8-10 months) so I don't have to worry and will plant them about the same time as I plant the garlic.
Potato onions, Allium cepa aggregatum, are similar to shallots, but larger. A single bulb, planted in the fall, emerges in the spring and eventually divides into a cluster of at least 3-5 bulbs, maybe even 10-12 bulbs, giving you a big "multiplier" effect. Potato onions are not grown commercially because they do not plant or harvest easily and are not suitable for commercial growers. But they are ideal for home growers. Despite that, they were almost lost, but SESE reintroduced a strain that dates back to 1790.
The bag of onions I received was eight ounces (227 g) and the bulbs varied considerably in size. That is OK because potato onions do not grow like garlic, where you are always selecting for size. From what I have read, large seed bulbs will tend to produce a large number of smaller bulbs, while the smaller seed bulbs produce 2-3 large bulbs. So regardless I will wind up with a variety of sizes in the harvest.
The origin of potato onions is not known, but they probably came from Europe with settlers in the mid-Atlantic states. They are still planted in the UK where they are called Egyptian onions (but are not the top-setting onions we refer to as Egyptian walking onions). The name seems to indicate their probable origin in Egypt.
The advantages of potato onions to the home gardener are many:
- They are easy to plant and easy to grow. Just plant bulbs in the fall and harvest in the summer when they go dormant and their foliage dies down. They can also be planted in the spring if needed. They are very cold hardy so fall planting is not a problem in northern latitudes.
- They are almost trouble free, but onion thrips and onion fly maggots can still be a problem. The thrips like hot, dry weather and the maggots like it wet.
- They are not day length sensitive and can be grown in most areas of the US, except southern Texas and Florida.
- They are supposed to have a sweet, mild taste, less pungent than seed onions. And they peel easily, easier than shallots.
- They are productive, producing, by various estimates, 3-5X to 8-10X the quantity planted, by weight (figure 5X as an average).
- Sizes range up to 3-4 inches in diameter, which is pretty good size, big or bigger than the seed onions I grow. You get a variety of sizes from each cluster, which home cooks like but commercial growers hate.
- They store very well, staying rock hard into spring..
- You save some of your crop for seed so they are a one-time purchase. Since the onions are grown from divisions, they tend to have a very low rate of bolting. The scape does not come from the center of the bulb, but rather from the base of the onion, so it can be removed without affecting the quality of the bulb.
While searching for cultivation information on multiplier onions, I re-encountered Michelle's spotlight article on L'itoi onions, another rare multiplier onion. Baker Creek was still showing an out of stock message but the original source, Native Seeds, had them in stock and I ordered a couple of packets (about ten tiny onions in each packet). I figured if I have to find space for potato onions, I might as well try this one, which I hope will provide some green onions before the bulbs go dormant. That would be a nice supplement to the potato onions, where bulbs are the goal.
Since it is adapted to high desert conditions, and probably does well in Michelle's climate, it may well be a challenge to get it to survive a New England winter. But if they do, given our desert-like conditions this summer, maybe they will like it here. As a back up, I plan to put a few of them in a pot to keep indoors.
The bulbs are small and pinkish, with some having a bluish cast. You can see some of the bulbs are already twinned with two independent sprouts emerging. There is not a lot of planting information available, but my plan is to plant them in the raised beds with six inch spacing, or four per square, the same as I do garlic. Both of these onions will go in the garden with the garlic, but it may take a year to evaluate the results. You have to be an optimist to be a gardener.