We now offer four varieties of Tree onion, and they are quite different in terms of crop volume, how the bulbs grow and how strong they are against rust fungus. Try them and see which one fits best where you live!
Hybrid and walking “spring onion”
Tree onion (Allium x proliferum) are hybrids between common chives (Allium cepa), ie yellow, red, shallot and white onion, and on the other hand spring onions (Allium fistulosum). These two species have been cultivated side by side for hundreds of years, and hybrids have thus emerged which have then been spread through use. They sometimes form flowers, but as far as we know the seeds are sterile. So vegetative propagation is what applies here and that gives this type of plant its character. The plant is fun and easy to cultivate, since you just have to plant the top sets and then it will just spread. It is best used in the same way as spring onions as long as it is fresh and fine. The stems that form the top onion become, in the same way as spring onions, stiff and unusable as food.
In English it is called i.a. Egyptian onion, Tree onion and Walking onion. The latter because it eventually becomes top heavy and bends down. Then the bulbs often take root, and so the plant can wander around in your garden at a speed of about 0.5 m / year.
There are probably thousands of hybrids in circulation in the world, but many are probably out of use as fewer people grow food themselves. The ones we have mostly come from the network around the Genetic resource center in Nibio, the former plant clubs (now the association Kvann). Whether there is a point in developing new varieties remains to be seen, but it is at least interesting to take care of those that already exist in the Nordic countries and test them in different regions.
Three varieties and their rust resistance
Here is a comparison of 3 of the varieties as they behave in Maridalen (Oslo), from left in both pictures: ‘Sunnfjord’, ‘Randaberg’ and ‘Dømmesmoen’ (This we have learned originates from the collections at Dømmesmoen in Grimstad, but they say there that they do not know the name or origin of any of the varieties they have. We have only begun to call it that, then a future genetic analysis may perhaps clarify the situation).
The left picture is from July 7 and the right from July 31. ‘Sunnfjord’ is the most productive, but is in return destroyed by rust fungi towards the end of July. Then gradually better over to ‘Dømmesmoen’, which is less productive, but in return remains usable all summer and is very rust restant.
The growth habit of the top sets
The top set bulbs also behave differently. ‘Dømmesmoen’ stands out by shooting from all the bulbs at the same time and quite early. ‘Sunnfjord’ prioritises one bulb, and this makes it easier to get several levels or branches. Hence the name of the plan Tree onion, and in norwegian “Etasjeløk”. Some also call it something like “onions for retired people” (Pensjonistløk), because you do not have to bend down to pick the top sets.
As mentioned, we have a fourth variety that is from Odalen. It has not yet grown in the garden at Sørbråten farm, but at Snippen about 100 m higher and with a quite different local environment, so it did not make sense to include it in the comparison above. But it seems very promising, so we’ll see next year.