The Long Island Seed Project

Alliums:  Onions, Scallions and Leeks

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Allium Seed Production
Egyptian or Walking Onions
Bulb Onions
Scallion or Green Bunching Onions

Revised June 25, 2007

Allium Seed Production

Being a biennial, most alliums (members of the onions family) must go through a dormant storage phase before they flower and produce seed.  It takes usually two years.  Garden chives and some scallions are perennial since they keep dividing and producing larger clumps and can produce seed crops every year.  With leeks, they are best overwintered in cold storage and kept green although there are very hardy kinds that survive over the winter in the field at temperatures way below freezing.  Some kinds of scallions (the term scallions is often used to describe an immature onion or a different species which do not produce bulbs) should also be overwintered like leeks.  Again, there are some very hardy kinds that winter over well in the field.  The tops of many bulb onions will die down in the summer and then the bulbs are lifted, cured and are stored over the winter in a cool and dry area wherever your cooking onions best keep. In the spring, plant the bulbs outside. They will send up flower stalks and will flower on floppy stems in early or mid summer. When the flowers are pollinated by insects (for seed purity, grow only one variety of onion), dozens of small seeds form on the flower head. Wait until the heads begin to brown (you may begin to see the black seeds exposed), cut the stalks and hang upside down in a loose (allowing the escape of moisture) paper bag or sack. The seeds will fall into the bag for next year's crop. The seeds will fall off the head for a number of days since ripening takes place over a week or more. When the seed head is completely dry roll them back and forth in your hands to dislodge remaining seed. Then screen and winnow.

There are hardy winter leeks and less resiliant summer kinds.  You may not know the hardiness of the leek you are hoping to save the seen of.  A safe way to overwinter the leek is to dig them out of the ground and store the entire plant in a cold environment above freezing and humid enough to prevent their roots from drying out. A potato storage area or root cellar would be a safe bet. For a few roots, wash the leeks, trim the tops as if preparing to sell them at market and put a bunch in the vegetable area of your refrigerator until spring if you can spare the space.


Onerwintered leeks will send up a flower stalk and produce a spherical unbel that will bloom in mid summer. Sometimes the allium stalk becomes top heavy with the large umbel of flowers or the stalk weakens at the base causing it to flop down so you may want to stake them to keep them upright.  The Saint Victor Leek we have been raising seed crops of for years produces huge light lavender heads that are truly beautiful in late June and into July.

Alliums are pollinated by flying insects which spread the pollen over long distances.  A seed grower can raise several kinds of alliums and maintain purity only if the alliums are of different species.  Bulb onions are Allium cepa, Leeks are Allium ampeloprasum, Scallions or Green Bunching Onions are usually Allium fistulosum and Chives are Allium schoenoprasum.  Insects will pollinate the flowers and leeks will cross-pollinate with other leeks. Onions are in the same family but are not the same species and do not cross with leeks. The same is true of chives and some kinds of scallions which may or may not cross with bulb onions depending on the species. To raise a pure seed crop of leeks, plant only one variety of leek or isolate your leek patches as much as possible to prevent the exchange of pollen between different varieties. Planting different varieties of the same species 50 or 100 feet apart will limit crossing but it won't eliminate it and that might be fine for the needs of the typical home gardener.

We are always trying to foil the long range pollination by insects since we don't have the ability to separate by long distances. Delaying the flowering of one variety so that it flowers only after the other finishes is one option (plant one earlier or later). Planting in blocks instead of rows and then selecting seeds from the interior of the block helps. Planting two varieties with barriers between the members of the same species; plant one variety on the east side of the house. the other on the west side. The barrier can be netting with climbing beans, a corn patch, etc. Make it a challenge for pollinators to find the other variety. Bees can roam long distances but they are efficient creatures and would rather harvest pollen and nectar from all the flowers of a certain type in the same patch.  Alliums that overwinter such as scallions, bulb onions and leeks flower all about the same time and early enough that corn and climbing beans are not yet effective barriers to insect flights so it is not so easy to use these types of strategies.

There has been much said about the viability of allium seed, leeks, onions, scallions, chives, etc. Unlike many kinds of vegetable seeds, their germination may decrease substantially after a year or two. Seed viability improves if the storage conditions for where the seed is maintained is cool or cold and kept dry. Don't subject seeds to dampness and extremes in temperature especially high temperatures. Many seeds including leek and onion seed store very well once the seed is dried for storage and then placed in storage under the cold conditions of the refrigerator (40°F). Place several packets of different kinds of seed in a jar on a day when humidity levels are low, seal with the lid and just put it in the fridge.

Egyptian Onion or Walking Onion

For many years this was my favorite all purpose onion.  Always just outside my kitchen door, the patch of walking onions (Allium cepa var. proliferum) was there in summer and in winter to quickly grab a handful of greens that I could toss into omelets, burgers or salads.  Even the little topsets I could use like garlic cloves in my cooking.  There are a few different varieties, all old time selections.  In my parents garden they were real tall (or maybe it's because I was so short), the strain I have from the old Pilgrim State Hospital Farm which was in Brentwood and is a strain also from the 1950's was shorter but more aggressive spreaders.  I have seen some kinds that even produce a few usually sterile flowers in among the topset bulbs.  The in-ground bulb divides to produce clumps on onion greens.  In late spring they send up their "seed" 2 foot high stalks which bear a cluster of small bulbils which will send out shoots as well.  The top-heavy mass topples to the ground where the top set "bulbils" root and help to form an ever expanding patch.

Some folks find the onions a bit hot for their taste but not me and like any onion, once used in cooking they become more mild and sweet.


Leeks are versitile in use and easier for us to store and raise seed crops than bulb onions.  They are very pleasant used in salads, minced for their mild flavoring or on the barbeque during the summer when they are still small.  A row of leeks nicely tended and hilled to blanche those beautiful thick stems really pays off big in the fall and winter when those frosty days call for a bowl of hearty potato leek soup. Leeks find their way into many of the winter dishes I prepare. Often I'll use them like a mild onion as a flavoring or when I am doing a stir-fry or tossing a massive stem into the roasting pan to make a great gravy or in winter stews.  One doesn't use the large leafy part on the leek because it is tough.

For a seed crop we have a mass cross of the hardiest of a dozen or so varieties that winter over here in the field. The summer leeks are too tender to survive the lowest temperatures, which can dip down to 10 degrees F. in early to mid January or even below 0.  We expect to maintain as much diversity in this mix as we can to get leeks that serve a number of culinary purposes for us.

Leek seed is sown in late winter or early spring indoors in seed flats and later transplanted to the garden.  They respond well to good garden soil rich in organic material.  To produce long white shanks you can begin to hill the plants early on.  The hilling will also protect the leek during the winter.

We also save the seed and continue to improve Saint Victor, an ancient European Leek which performs well for us and always yields quality leeks for the table, beautiful lavender flowers and a bountiful seed crop without any fuss.  Saint Victor is an odd kind of leek in that the normally gray-green foliage develops a pronounced purple cast after frost which is maintained during the winter.
We noticed that St. Victor can produce in the second season a cluster of very large and pleasant tasting garlic-like cloves at the base of the stalk as the shank of the leek breaks down and just before the flower stalk is produced. We discovered the bulbs when we pulled about 70% of our overwintered St. Victor crop out (selecting for the best purple foliage) in April. The cloves are a lot like the huge elephant garlic that you see in produce markets which is, interesting enough, in the leek family, not a garlic. I wonder if this is the "bulbing" characteristic that has been selected against by modern leek breeders? Heirloom leeks are looking better and better to me. Another very old kind that I obtained from friends in Europe produced a head with only a few flowers but hundreds of tiny bulbil topsets. Very neat. Chance discoveries like this will often send me into a new direction of selection and my breeding objectives change. I never imagined that I would have so much fun with leeks of all vegetables.

Bulb Onion

I really ought to specialize in a particular crop, maybe that would allow more time to produce significant breeding accomplishments, but the truth is; that in growing each diverse batch of vegetable seed, especially the less modern varieties, there is so much to discover and it is just so fascinating. We haven't done much with saving seed to produce bulb onion (Allium cepa).  I would like to, perhaps in the future we will.   At latitudes of 40° and higher we grow long day onions or day neutral types.  Long Island is at 40° N which is about the same as much of Spain and Italy.  We have successfully grown onion seed; in fact, from Spain, Italy, Japan, England and Austrailia.  There are also really fine kinds that were developed in the 19th century in Connecticut and Massachusetts and New York Early is a variety from the mid 1900's which is a good keeping variety still worth growing We managed to produce a small seed crop.  Our local onions tend to be selected for fertile river valley soils or muck soils and don't always perform well on the sandy soils in our gardens.  Grow onions fast on rich soils with ample moisture.  We sow seed early (late winter) to obtain nice sized transplants which go into the garden in spring.  That allows the onion to produce early green onions in late spring and then begin to bulb up in the early summer during the long days for the fall harvest.  Young onion seedlings and transplants require care.  They do not compete well with weeds.  The best storage kinds are the "hard " onions which are good all-purpose cooking kinds.  The large sweet kinds such as the Spanish Onion and the many developed from this line tend to be poorer keepers.  Most bulb onions tend to winter over poorly in the fields for us although the Italian "Torpedo Onion or Bottle Onion" from Florence in both red and brown skin forms seems rather hardy and have produced seed here.

Hard onions properly cured and dry after harvest will usually last the winter in a cool but above freezing location.  In the spring they can be planted outdoors for a seed crop which ripens in July usually.

Scallions or Green Bunching Onions

Scallions are used for the tender greens.  In some cases they are produced from young bulb onions (Allium cepa) and there are some kinds of bulb onions that can be used for both the green scallions and later on, the developing bulbs.  The mild White Spanish Onion is a nice dual use onion. In fact, there are a few beautiful related white onions that produce nice green scallions that can be marketed with their white bulbs. I would like to look closely at these summer onions someday.

  One of the easiest sustainable bunching onions is the true scallion or Welsh Onion (Allium fistulosum) which is actually Russian, I am told.  Some of the nicest Welsh Onions have been developed in Japan and are essentially perennial.  They are winter hardy (maybe because of Siberian ancestry) and the roots although never bulbing, produce new green onions by division.  The Welsh Onion can also produce copious seed.  We grew several strains and found variation in flavor and texture.  We are now growing a very mild crisp selection which seems to just get better each year. Home produced onion seed. What can I say? You can't get fresher seed.

Last Modified:  June, 2007