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How long do sunchokes need to form tubers?

Posts: 356
Location: Portugal (zone 9) and Iceland (zone 5)
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Hi, I seem to have trouble growing Jerusalem artichokes (sunchokes).

I planted them in May (when the soil thaws in Iceland), and they grew very well and have reach 1 meter (3 foot) high. No flower buds. I started with store bought tubers. They sprouted easily in May and grew very fast and tall.

As frosts are now beginning in Iceland, I had to dig my potatoes (a nice crop within only 3 months) and then I decided to also dig some sunchokes, but surprise, I found no tubers other than the original one. I have many plants and I only dug a few.

Anyones knows what might happened?

My guess is that they need much more time to form tubers. The 3-4 months is not enough, perhaps they need 6 months. The soil is fertile. It's already the second year of failure. Last year, I wait until November (when soil froze) and I also had no tubers. I have seen some slugs in their roots, but I don't think they are the main reason for the failure.

I can say potatoes 2-0 sunchokes, in Iceland. Any ideas?
Posts: 582
Location: Lower Mainland British Columbia Canada Zone 8a/ Manchester Jamaica
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sunchokes you don't attempt to dig until first forst, especially if your in a short season. They often don't set tubers big enough to eat when strugling but the ropes you find between the tubers often sprout if they close enough to the surface. I grew 10 last year and found about 15 tubers and thought i over harvested, this year 20 grew from those rhizomes i reburied. They will overwinter even in iceland, i found when they came up naturally they grew allot better than when i stuck em in the ground late in the season. I put the bed where i had them under 8 inches of straw and i thought i killed it. They came up later than i thought but have now reached 12 feet without falling over. If your plants arn't that big leave them for a better start next year. digging around in a low yielding bed only gives rize to distrubed baby tubers. I've only gotten them to flower once last year and is was only 2 of twenty, they tend to need a true long season to flower when they prefer which is in sep/oct/

I topped my plants this year to see how extra side shooting effects tubers and flowering, but really i just wanted it to grow more green for the ducks and rabbits without falling over.
Posts: 4437
Location: North Central Michigan
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there are many variables, but in Michigan I find that they are much better the second year..much larger and tastier. I have moved mine so many times that they don't get much of a chance to get very big, but I have had some in the same places for a couple years and they get emmense root groupings in a couple years..
Posts: 1
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Hi Paulo,

I think I can explain why you're having troubles with JA (short for Jerusalem Artichokes).

You don't say which named variety you planted so may I safely assume those were store-bought tubers? If so they probably come from an icelandic greenhouse or better from continental europe and so they are of a variety optimized for giving the maximum yield under optimal growing conditions which at the very least means frost-free days until mid November.

You see, JA are really short-day plants which means they usually flower AND tuberize only when they receive less than 12 hours of light (past September, 23 to be precise).

Under long days JAs perform vegetative grow and store sugars into their stems, under short days they translocate such sugars into tubers. Flowering terminates the accumulation of sugars and marks the onset of a senescence syndrome where stored sugars and proteins are dismantled and used to enlarge overwintering tubers.
Note that tuberization and flowering are actually independent processes and tuberization may start before flowering for particularly late flowering varietis: in this case sugars are directly sent to tubers while photosynthesis is still at peak rate!
The most productive JA varieties under temperate climates of course tend to flower very very late and tuberize under 12hrs so that they can maximize sunlight usage until late fall.

For this precise reasons your JA stand no chances of producing anything outside in Iceland: their aerial parts are killed by frosts before they begin to form any tuber.

However, there is considerable genetic variability in this genus: there are early flowering varieties in full bloom with 14 hours day lengths, two of them growing as weedy clones near my place (Italy, by the way) and there are even dayneutral cultivars which actually flower independent of daylength, depending only on plant development stage.
These flower about 4-5 month earlier than anything else.

Before giving up I suggest you look for dayneutral cultivars: there are actually three of them probably within your reach, they are "stampede" from the US, "bianca" from europe and "dagnøytral" grown in Norway and at my place.

Dagnøytral in particular is the only JA variety I know of that actually produces acceptably sized tubers in Norway. It is worth giving it a try.
I see you strive to reach self sufficiency so maybe you could be interested in a research project on jerusalem artichokes: my group aims at developing a sub-arctic adapted JA variety.
Anything flowering earlier than the current dagnøytral is acceptable, moreover dwarf varieties stand a better chance of delivering in long days or even continuous light with very short growing seasons since plant maturity may occur relatively fast.

Would you be interested in participating? (if so PM) If you want, I may send you a couple of dagnøytral tubers for testing next growing season, just make sure to bury them so they don't dry and die.

Don't misunderstand my intentions: I'd like to hear if dagnøytral may already deliver in Iceland for a very precise reason. One day I'd like to move there and start my own organic farm without expensive greenhouses for the main crops.

thank you for reading!

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