Q: I would like to ask you about a couple of things you mentioned in your talk last night – one was about there being no such thing as short-day onion sets. I have purchased what I understand ARE just such a thing. Here is one source:

http://www.dixondalefarms.com/category/short_day_onions

and Green Thumb in San Marcos, who is good about providing seasonal/geographic appropriate plants sells the bunches, too. I have planted them using the trench method that Dixondale recommends and everything looks very good so far!

A: Thank you for sending me the link to a nursery that carries bareroot plants of short-day onions. I too have purchased these but they are not sets, they are bare-root onions,  (also sometimes called bareroot transplants.) Onions are biennial plants which means they take two years from seed to flower after which they die. However, there exists no wild plant exactly like a cultivated onion and this is because these plants have adapted over thousands of years to being cultivated by humans. Thus they also have some unique characteristics. Onions are a complicated cool-season crop and often misunderstood, but I explain them in detail on pages 386 to 389 of my book.

Onions are sensitive to day-length and temperature and they come in long-daylength, medium-daylength, and short-daylength varieties. In order to grow a globe onion it’s important for gardeners know which varieties are adapted to their area. Gardeners who live in cold-winter climates in northern latitudes should plant sets of long-day onions.  Gardeners in the central latitudes of USA such as the California Central Valley should grow medium day-length onions. Gardeners in southern latitudes and warm-winter climates such as ours need to plant short-day onions. As I stated last night, sets of short-day onions cannot be purchased and the reason is, it is impossible for a short-day onion to make a set. Short-day onions are subtropical plants that continue to grow throughout winter and never go totally dormant. In order to make a set, an onion must go totally dormant as do long-day and medium-day onions that are adapted to cold-winter climates.

Last night I said that in order to grow a globe onion here we must choose a short day variety such as Grano or Granex (or others mentioned in my book) and plant seeds of short-day onions in early November, later transplanting them at the correct spacing in a different row in January. Or alternatively if we forgot to plant them from seeds we should purchase short-day onions as bareroot transplants from local nurseries. (I neglected to mention catalogues. Thanks for mentioning catalogues as an additional source.) Unfortunately, since I was speaking on warm-season crops I didn’t have time to go into onions in great depth. Your excellent question helps me to do this now. All we need do is define terms:

Onion sets are small (usually 1-inch diameter) round bulbs of long-day or medium day-length onions covered with a brown or white papery coat, according to variety.  Unlike short-day onions, long-day and medium-daylength onions go completely dormant in winter of their first season of growth. They die to the ground in late summer or fall leaving a small bulb called a “set”. Onion sets have no leaves or roots attached. To create onion sets, growers plant seeds of long-day or medium-day onions in fields in spring and harvest the sets in late summer or early fall after all foliage has dried off and died.  After harvesting the sets, they pack them in string bags or large sacks for sale to farmers and gardeners throughout the world. Onion sets keep without refrigeration for 6 or 7 months through the winter months until the following spring when farmers or gardeners plant them in fields or gardens for summer or fall harvest as full-grown globe onions that are good keepers in winter.  But these sets will not make globe onions in Mediterranean climates nearer the equator, such as Southern California because they are the wrong varieties to make a globe onion here. In Southern California and other southern states and similar latitudes throughout the world, including Hawaii, plant sets when you want to grow scallions only since they won’t make a proper globe onion because of lack of the correct day-length during the growing season.

Bareroot onions are plants of short-day varieties that were planted from seeds in fall and dug up when the weather got cold, but before there has been any frost. After digging up the plants, growers remove all the earth from their roots leaving the roots and the green leaves attached. They tie the bare-rooted  plants together in bundles with roots and green tops left on them and they keep them cold or under refrigeration, but without freezing, until it’s time to ship them to nurseries ahead of our January bareroot season. These bareroot, short-day onions, such as you purchased, do not have a bulb. Instead, they have long narrow shape, similar to green onions, with no bulbous shape at the bottom.  Local gardeners can purchase these bareroot transplants in nurseries in warm-winter climates in January. It’s important to plant them as soon as you purchase them. Unlike onion sets, they don’t keep long.

I hope this clears up the confusion and am glad your question gave me the chance to explain.

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