Let’s get this clear right from the start: Jerusalem artichokes are neither artichokes nor from Jerusalem. They are beautiful sunflowers, that not only brighten up your landscape, but also provide a tremendous edible bounty. If you’re a forager who also likes to garden, this is the plant for you. Growing from four to ten feet tall, sunchokes have classic, yellow, daisy flowers and tasty tubers. Three physical characteristics of their above-ground parts make them easy to differentiate from other sunflowers:
1) The ray petals at the center of the flower are yellow, not black or brown,
2) the leaves feel like sandpaper (no way to show you that in a photo), and
3) the leaves are joined to the stem by winged petioles. Petiole is another word for leaf stem; notice how it gets wider (wing-shaped) as it approaches the leaf blade.
Jerusalem artichokes are a gateway food for beginning foragers. You can buy the tubers for sale as vegetables in farmers’ markets and grocery stores, and you can also find them as ornamental plants at garden centers. There’s no difference between the tubers sold in different venues, although most people who grow them as ornamental garden plants never realize they’re also edible.
Jerusalem artichokes are aggressive growers. If you grow them at home, do yourself a favor, and dig up at least half of the tubers after the first frost. Not only will they grow better that way (after being thinned and divided), but this will also prevent them from taking over the universe. Here’s an example of how quickly they multiply: I planted 8 tubers in a container last spring, and earlier this week I harvested more than 60 edible tubers from that same container. And that’s not counting the tubers I planted back in the ground.
Sunchokes can be harvested from fall to spring, as long as the ground isn’t frozen solid, making them impossible to dig. From spring to fall, when the plants are in active growth, the tubers are smaller, less firm, and less tasty, because the plants are drawing on the reserves of nutrition stored in their tubers.
It’s important not to harvest sunchokes before they’re ripe, or their starch (inulin) might cause flatulence. (Dare I mention that some people call them Jerusalem Fartichokes? I guess I do dare.) That’s why most people wait until after the first frost. If you live someplace frost-free, wait until late October to harvest, just to be on the safe side. Thorough cooking also reduces the risk of excessive gassiness. Don’t let my warning deter you from trying this delicious food. I’ve never had a problem with them, but I feel it’s my duty to let you know it’s a possibility.
People who expect j-chokes (this plant has a lot of nick names) to be a potato substitute may be disappointed. The texture of a j-choke will never be light and fluffy like a russet potato. But the flavor of Jerusalem artichokes is excellent, and here are a few ways to use them that highlight their flavor and makes the most of their unique texture:
1) Fully ripe Jerusalem artichokes are sweet and crisp when raw; slice them thinly into salads or add sunchoke matchsticks to a tray of crudités.
2) When baked, sunchokes become almost liquid inside. They can also be cooked in a crockpot as part of a soup or stew.
3) Boil the tubers in milk, purée with a little butter, salt, and pepper. You’ll have a smooth, creamy side dish.
4) Make roasted sunchoke soup. It’s fall comfort food.
5) Puréed sunchokes make a superb soufflée.
6) Use grated sunchokes instead of carrots in this delicious sunchoke cake.
7) Try making oven baked sunchoke chips.
Do the flowers have any medicinal properties? If so, can i dry and tincture them?
Thank you
Not that I know of. I’m not an expert with medicinals, but I’ve taken a few medicinal plant courses and I’ve never heard of anyone using the petals. Still, to be absolutely sure, I’d check with an authority on the subject. I’m all about the flavor and the food!
I haven’t found any historical or scientific record, only hearsay that the Native Americans made tea from the leaves and the flowers. The leaves of mine always have powdery mildew so I’ve never tried them, but I’ve eaten the flowers of the eastern varieties and made wine from them. The western varieties will grow seed and their flowers are spiny and have a nasty resinous taste. The flowers of the eastern varieties never seed. They taste like the roots but stronger. Some varieties are tender enough to toss raw in salads, some are so tough only a goat could chew them! When I first boiled some flowers for wine the smell was so familiar. My wife came home and asked me why I was cooking squash … that was it! They resemble squash when boiled or steamed.
My sun chokes have not looked good this year (dying and yellow leaves) and have yet to start to flower. We live in the desert and last year they had already started flowering in September. If the plant never flowers are the tubers still edible?
Thank you for your guidance,
Amalia
Yes, the tubers are still edible even if the plants never flower.
Petals are rich in lutein
Before flowering the Green buds go in my soup.
Can you eat the leaves? I know with sunflower as long as you blanch them to remove any unhealthy bacteria, which they tend to carry, you can eat the leaves.
Hi Michelle, I don’t know! It’s hard to imagine eating the leaves, which are VERY rough and sandpapery, but it’s possible the texture would be fine after cooking. Steven Barstow (Around the World in 80 Plants) says the young stems are edible, but I haven’t heard anyone talk about eating the leaves. Please let me know if you find out.
Yes, when it’s a half meter tall, you take the highest leaves that are soft, and make a soup. They are edible.
I’ve got two varieties, a white knobby Stampede with palm sized leaves and a red smooth Fescue with huge leaves. I’ve tried them both fried and boiled. Fried they crisp up and actually melt on the tongue! They took on the flavor of the olive oil, so I’d say some herbs and/or spices tossed in would improve them. The rough hairy texture disappears. Boiled, they taste exactly like squash. A little butter and black pepper and YUM! After a good 5 minutes the hairy texture is gone too. I’ve heard that they can be used like grape leaves as wraps in traditional Mediterranean cooking. I’ll be trying that too.
The greens contain trace amounts of salicylic acid, raw aspirin and coumarin, raw Coumadin or Warfarin. That means don’t eat huge helpings without a break in between if you’re already on blood thinners.
I’ve ground raw dehydrated chips in a food processor and made flour that’s much like Buckwheat flour. You have to mix it with wheat to get it to raise and it’s best mixed with other flours for flat breads. Mixed with pizza dough stiffens the crust up nicely. Some raw chips tossed on the pizza before it goes into the oven make a nice crunch and flavor change.
I made wine from tuber broth. It was very stout for a drinking wine, but it made a decent cooking wine. I make wine from flower broth that’s good straight or blended with fruity wines.
I’ve tossed them into jars of pickled beets and eggs. WOW! We can most of ours as pickles and relishes and we prefer them to cukes!
Worldwide there are at least 200 varieties. I have three I’ve gathered locally in west-central Pa. Two are nice mild tasting, good any which way while the third one has a super strong turnipy-potatoey-Sunflower seed flavor that stinks up the kitchen when they’re cooked. They are so strong just a dash in soups, stews or roasts is plenty. You’d either like them or hate them.
I’ve also made flour from dehydrated chips, but never thought about making wine…nice idea! This is such a versatile tuber, and I’ve tried loads of ways to use them. But I love them so much as a mash, I can barely bring myself to eat them any other way!
I’m planting sunchokes this year for the first time, and I’m truly excited! I want to know if anyone had ever grown them together with ginger. Really I want to know (if i should, or should not) . I mean, they both require the same soil and growing both are slow. It’s a 25 gal smart canvas pot, so it’s huge… and i think it would be alright…yeah or ney ???
Hi Karen, I’m not sure why you think sunchokes are slow-growers but they aren’t! These are plants that could easily take over the universe. They multiply 5-10 fold in every growing season. My first year I planted 10 tubers in a container and since then (3 years later) I have more than I can grow/eat/give away. They might be able to share a smart pot with ginger the first year. But after that, they will squeeze the ginger out, unless you harvest 80% of the sunchokes every fall. Are you considering tropical ginger or perennial ginger, and where do you live? I ask because if you live someplace with cold winters and are thinking of growing tropical ginger as an annual, you’ll be fine. Otherwise…the sunchokes will out compete the ginger for sure.
There are between 200 and possibly 400 varieties of Sunchokes. I have three. One has stolons, the rhizomes that the tubers grow on, that are very short. This clusters the tubers very close to the stalk and form right on the root ball. Another has stolons that reach out around 10″. The third has stolons that reach out around 20″. Needless to say, the ones that spread 20″ in all directions spread very fast from year to year, unless contained and probably would not do well in containers. The ones that don’t spread very far would do nicely for containers, but, because they grow on short stolons or right off the root ball, their ends are susceptible to rot more-so than ones that grow on longer stolons.
As to mixing them with Ginger, give it a try and let us know how it goes. Sunchokes are Allelopathic. That means that they also spread a chemical, like Walnut trees, Glassweed and several others that retard germination of competing seeds and restrict the spread of many rhizome plants. In my established patches, most grasses don’t spread in, Lambsquarters, if they germinate, only grow about 18″ tall. Strawberries however spread into the patches unhindered and Field Garlic holds its own with no problem. Perhaps Ginger will grow with it … or not. There’s one way to find out!
Interesting. My sunchoke tubers mostly grow close to the base of the plant, producing clusters of multiple tuber 6-8″ wide, but they also send out rhizomes that form additional tubers. The sunchokes are surrounded by Centranthus ruber, Mahonia, currants, and Thelosperma megapotamicum. I haven’t seen any adverse effects attributable to allelopathy. At least not yet!
Ah I thought they all bloomed..they are not in very garden centre. So when I spotted them in a a fruit and vegetable shop I was deleted
Helen
Where can we find the varieties with the 10 or 20″ stolons, as mine are all 3 to 6″ stolons??
Hi Tim, Blaine is the reader who mentioned the stolon length, so you’ll have to ask him. I’ve never seen sunchokes with such long stolons myself, but that doesn’t mean they’re not out there!
Ask the suppliers. If they grow and harvest their own they should know details such as average size, range of size, distance of stolon spread, flavor, etc. If they don’t know I think I’d shy away from those vendors. As always, when you’re buying from a vendor, see if you can find any independent reviews of their products and services.
Thank you Blaine, I was hoping you’d chime in!
Just subscribed and so grateful for all these ideas!
The Jerusalem Artichokes I planted some years ago are moving into the edge of the vegetable garden and I’m trying to keep up. Giving them away has been a small problem, as I’ve only recommended drying them for storage, sliced or grated to dry more quickly.
I like the dried ones with eggs and in soups, and best of all (so far), drenched in roasted sesame oil and garlic with fresh herbs on pasta.
I read somewhere that they regulate blood sugar, and wonder whether this is generally known and true for all varieties?
Hi Shelagh, I’ve also read that jchokes help regulate blood sugar, but I’m not a medical person and have no expertise in that area. I’m all about the flavor! Can you tell me more about your dried sunchokes drenched in roasted sesame oil and garlic on pasta? Do you rehydrate them first? Are they grated? I’m intrigued.
Hi Ellen:
I’m not medically-trained either, but am interested in such things, and find the ideas of food-as-medicine add to the enjoyment. I’ll still love the artichokes for providing so much with zero care and attention, and their nutty taste when dried. To me, the flavour improves with drying. Nutty and a bit sweet.
I usually do both grated and sliced batches, just spread out on some plastic grid racks and wrapped loosely in muslin to keep insects off. A food processor does the slicing or grating in minutes, so they just need a scrub. Every few days I open the cloth and stir them around a little. They dry quite quickly, and the slices are like chips.
I use the grated form for the pasta because it goes into the twirls of the spiral shape I like, but the chips could be good with spaghetti. They are also good to add to salads and eggs and fish…
As to prep:
If I think of it early enough in the day, I put a handful or 2 of the grated dried artichokes into a dish, splash on enough sesame to coat the little bits, mix it around, cover and let steep. After a few hours, some oil is absorbed and they have a slightly chewy texture, which is great with the pasta. Fresh chervil and tarragon are wonderful with this, as is roasted garlic, basil, olive, pumpkin or other seeds and walnuts. Some salt and lemon is good, and it’s good cold or warm. The oil-mix is also a great starter for stir fry vegetables.
It’s pretty versatile, and I hope that helps.
I’ve also made a salt-fermented spicy condiment with the grated slices that was really good. Will look up that recipe. Thanks to those above with other ideas. Look forward to trying those.
many thanks!
This is my very first time to plan Sunchokes. I only have one sprout. Can I cut a stem and plan it?
I’ve never tried rooting cuttings of sunchokes, so I’m afraid I can’t speak from experience. If you try it, please let me know how it works.
Yes they are in sunlight from sunrise around 5.30 am at the moment til about 6pm. About 5 foot gets it til sunset at 9pm. The temp to day is 36c with thunder storms ptodicted mid week. Yes I just boringly make soup.
You can cut them just like potatoes. Each piece must have a node like each piece of potato must have an eye. Plant them about 2″ deep in loosened soil in a good sunny location.
This is true, but I think Sandy was asking about a stem cutting. Without a piece of the tuber containing an eye, I’m not sure if it’s possible. Blaine, have you ever tried a simple stem cutting?
I’ve never tried a stem cutting either. I read where the top of an annual sunflower was grafted onto the root stock of a perennial sunchoke and the sunflower seeds yielded much more oil, but I’ve never seen where anyone has tried rooting a stem cutting. As it’s a perennial, that could be interesting to try with rooting hormone.
Hi there! Grateful for this wonderful resource and forum. As to the planting, I see above you said in spring, but could someone take one of mine now and plant in a garden or pot and they would survive? Or better to give my friend tubers to plant next spring?
I don’t know about you, but some of my sunchokes are 10 feet tall right now! You can certainly transplant now, but you’ll have to cut back most of the top growth to make that manageable. Just make sure your friend gives the transplant extra TLC because in hot weather that plant is going to need more attention. I don’t know where you are, but if it’s very hot, you should wait until it cools down.
Hi I have JAs as a privacy screen this is my second year. Last year it grow to 10 foot. It is in sunlight from dawn til dusk. Alas no flowers what am I doing wrong. (refers to it as green shit ????)) This year they are growing well nearly 6 foot high we have had high temperatures of late in the late 20 s to low 30 s in Southern Scotland. I have ordered a pH meter to check the soil
Regards
Helen
Hi Helen, Sunchokes are late bloomers. Mine haven’t started yet and aren’t usually in full swing until September. Also, it’s not unusual for the plants to need a year or two before they flower. Hopefully you’ll see blooms in 4-8 weeks. A few questions: how much sunlight are they getting? (Sunchokes flower best in full, all day sun.) Are you growing them for food as well as for privacy? (They’ll produce tasty tubers even if they don’t flower.) I doubt if soil pH is your issue, although it’s always good to know what you’re working with. Please keep me posted.
There are at least 200 varieties in the US with possibly 400 worldwide. There are a few that bloom irregularly and some that don’t bloom. In west-central PA., zone 5, mine started blooming a bit spotty about a week ago. Maybe 1/4 of them are blooming now. I’ve got three varieties. Two are blooming spotty now, the third won’t bloom for up to three more weeks.
Blaine, I found this on a permaculture board, which jives with what you’re saying. The original post was written by Victor Johanson of Fairbanks, AK, and I’ve copied his text below so you won’t have to scroll through all the other posts on that page:
“Stampede is usually considered the earliest of the named cultivars. I grew some here in Fairbanks back in the 80s and it bloomed the first year. I moved away, and they were gone when I came back eight years later. The last couple years I decided to try it again, so I got Stampede and about 10 other cultivars plus grew some from seed–nothing bloomed. I contacted Will Bonsall from the Scatterseed Project in Maine, and he confirmed that Stampede is his earliest. I got some from him, thinking that maybe what I got was mislabeled. I also read http://www.nordgen.org/ngdoc/plants/articles/Helianthus_tuberosus-Diversity_2010-1.pdf by Axel Diederichsen regarding the extensive collection maintained by the Canadian germplasm system. On pages 10-11 it is related that in 2008, a very cool year, only four accessions (of 160+) flowered. The paper also states that earlier flowering is associated with shorter plants and heavier tubers. I obtained three of these accessions and grew them this year. We had an extremely cool and rainy summer, and even though they were planted quite late, buds formed on two of them. The Stampede I got from Scatterseed looked different from the other one and appeared to be starting to form buds also. These observations lead me to believe that in a normal summer, at least some of these will bloom.”
Wow! I’ve looked this over and there’s a bunch of info buried in that article! Thanks Ellen.
I was hoping you’d like it!
Hi,
Should I cut off the blooms to increase tuber size? Or does that matter much?
I don’t know if that would work, but if you try the experiment, please let me know how it goes. Even letting mine flower as much as I want, some tubers are 5 inches across, which is pretty darn big.
The flowers are nice for the pollinators but I’ll remove 50% in one section and see what the results may be
Thanks
Hi! This is my first year to grow Jerusalem artichokes. I live in Louisiana and planted them in the spring. I have 10 plants and they were about 6 feet tall and had been flowering and still have some. Then hurricane Laura hit and broke some and bent and laid the others down. I am thinking about just digging them up and just cutting my losses. I dug around one of the plants and can’t feel any tubers. Are they deeper than I think and should I just wait until the first frost. Thanks
Hi Rhonda, We just had a super early snow here in Santa Fe and most of my Jerusalem artichokes were also knocked over! However, I’m cutting mine back rather than pulling them up because I want a good crop of tubers and now is when those tubers are forming and getting big and fat. You really shouldn’t harvest until after the first frost. The tubers aren’t usually very deep, I’d say they start at 4-6″. If you’re not finding any, they haven’t formed yet, and you should definitely wait. Good luck!
‘Chokes are tough. Let them go, if they aren’t snapped clean off, they’ll survive and if not broken they’ll straighten some or a lot. The tubers gain more size and numbers if you let the stalks die and dry. The stalk energy drains into the tubers as they ‘cure’. If your variety produces seed, then cutting the flowers off at the end of their bloom period will direct all the energy into the tubers. If your variety doesn’t seed, then it doesn’t matter if you cut or leave the flowers on.
How deep the tubers can grow depends on the variety of Sunchoke and the texture of your soil. Some have very long rhizomes and if your soil is loose, they can go a foot or more deep. Others have short rhizomes and don’t spread far or deep no matter how loose the soil, so until you get to harvest some mature tubers you won’t know what to expect.
Wait until the tops are dead and fully dried up before you harvest.
Rhonda, I agree with Blaine, mostly. We had snow on September 8th and my sunchokes were 12′ tall. A few snapped clean through, and I hoped the others would straighten up at least a little but alas, that was not to be. I think whether they’ll straighten up on their own depends on how tall they are to begin with, how sturdy the stems are, and how long they’ve been bent before you get to them and do some damage control. I ended up tying some up, and cutting some back to about 4-5′. It looks crappy, but I’m in it for the food.
Such inspirjng stuff here! My first intro to sunchokes was in a recipe for a hummus-like spread (along with chickpeas, butter and a few other things)—so delicious!
I will definitely look into what varieties are available to plant in Toronto. We have somewhat challenging growing conditions … our front yard gets plenty of sun, but my husband is not excited about anything that might look like a vegetable garden in the front yard, while I was frankly thrilled to pick some purslane, plantain, & wood sorrel for meals last year.
There is some ground available in the backyard, however it gets far less sun and is rather heavy, clay-based soil. Really not much more than a scraggly green patch at the moment.
Bringing some beauty to both front & back yards, with possible edible side benefits, is an inspiring thought!
Jerusalem artichokes might be the perfect way to start, considering your husband’s objections. Because they really just look like they’re part of a flower garden. Good luck, and please keep me posted!
Hard clay or lose loam only affects the Sunchokes in depth and size. They’ll grow just fine in clay, and over time if you build up the soil with either added material or the ‘choke tops they’ll improve amazingly in size and quality..They do need as much sun as possible. Their roots will draw soil goodies from surprisingly deep. If you’re in a rural area, or near one, and if you can wait until fall, look around for them. Fall is when they’re easy to identify.They’re native to our-your area (I’m in west-central Pennsylvania) from zones 8 to 3. I’m close to the middle of their range. You might be able to collect a few samples close by! There are a few dozen patches in my area from in-town flower gardens to some sunny patches scattered out in the woods and along roads. They range from 4′ tall to 12’ tall. Sample them before you commit to planting any. One variety I have is obnoxiously strong flavored with something like a turnipy-herbal flavor while the other two are deliciously mild, potatoey-sunflower seed plus something else flavored.
I’m very disappointed with mine this spring. the long odd fall we had must have been very favorable for slugs. Every one of mine have holes eaten into them. I’ll be scattering a lot of the sulfur bait around real soon.
When I lived in NE PA the biggest problem I had with sunchokes was the deer. I’d find them along the Delaware River, but almost never in bloom and they certainly never had a chance to bloom in my garden before Bambi nipped off the flowers. But I could still harvest the tubers. My soil there was a combo of rocks and clay, whereas here in NM it’s very sandy. Sunchokes are happy either way, asl long as they get enough sun and water.
Hi does anyone have experience with the flowers for flower arrangements – how long do the flowers keep for ?
Not me! I’m all about the food and have never used the flowers. But maybe someone else here will know.
They’re not exceptionally hardy. They last for around 4 to 6 days, but then I haven’t chilled them like the pros do. That might make a difference. They are exceptionally hard frost hardy so that might make a difference.
Anyone have hollow tubers? This was my first year growing sunchokes. I received the planting tubers last September and was told by the grower to plant them immediately, about 4″ deep and mulch heavily. I live in central SC, USA. Hot, humid summers are the rule but the chokes dud well in their large containers. Even the tops died back in mid-August, I began to dig the tubers. The containers are on my drip irrigation system and the plants received fairly regular fertilizer simply because of their location. Some were showing signs of rot, probably because we have to increase irrigation to our beds for other plants when the extreme heat starts in July. I harvested about 8 pounds of tubers from five plants but many of the large, hand-shaped tubers have hollow channels running through them. I’ve searched everywhere for information re whether of not these partially hollow tubers are still safe to eat? They have no rot showing just little hollow “trails.” Can’t find anything on internet or You Tube and my state agriculture department knows nothing about Jerusalem Artichokes so I’m in dire need of help.
I know this is long so thank you for taking time to read.
Hi Jarmy, very sorry but I’ve never heard of this happening and I’ve never seen it. I suggest you contact your Coop Extension office; maybe they’ll know more than your state ag department. One question: are the hollow tunnels running through the interior of the tubers, or is it possible that what you’re seeing are the spaces between the sections of tuber? Many sunchoke tubers are composed of multiple sections (they look like lumps growing out of other lumps). I realize that’s probably not what you’re seeing, but wanted to eliminate that possibility.
Hi Jarmy, west-central PA, zone 5 here. Only one year did I have slightly hollow or pithy tubers like radishes can get. We got sideswiped by just about every hurricane that fall. Our soil was soaked more often than well dried. Chokes do much better with just light to moderate water. They also store much better when they’re solid and firm. They are quite drought tolerant, but produce better and larger tubers with some, not a lot of water. See if you can get valves or flow reducers in the water supplying your ‘chokes.
I’ve never fertilized my ‘choke patches at all. I pull the stalks and surface tubers when the stalks are dead and dried and put them through a small chipper and spread the chips over the patches. When I go through digging for the rest of the tubers that pretty much turns the chips under and they compost in the soil and provide all the fertilizer they need. The first couple of years I composted the stalks with other compost and discovered them trying to start up where I spread the compost plus in the compost bins! I can say that the ones that showed up in the compost bins produced nearly baking potato sized tubers in the pure compost.
I grow JArtichokes in Bonavista Newfoundland https://www.google.ca/maps/@48.6543462,-53.1041573,16z. Last fall I uprooted half of the crop, washed off the soil, washed them in the washing machine (“delicates”!), drained them, and stored them in the two vegetable drawers in the refrigerator.
This winter I have worked my way through them making vegetable soup. Garlic, 1 lb onions diced and caramelized, 1.5 lbs carrots diced throw on top to steam. 3 lbs artichokes diced throw on top to steam. Add sauce: 370 ml tomato paste, water, corn flour and/or spices to taste. I preserve mine, bottling it for use.
I find that about one artichoke in ten shows a jet-black colour on an extremity; I chop this black bit off (to the vermicomposter!).
Please and than you: why am I finding jet-black colouring?
For the time being I assume it would not be good for the tummy (“If in doubt, throw it out”)
Cheers, Chris
Hi Chris, First of all: wow! In the delicates cycle. That is some creative thinking. I may try that next year. I, too, find the black coloring on the tips of some tubers; these areas are also soft. I trim these parts off (they’re rotting) and almost always still have a solid white, usable part of the tuber to use. Are the black parts on your tubers soft or shrivelled? There are several things that could cause this: 1) physical damage from a shovel or animal, 2) cultural conditions, e.g too much moisture, or 3) there are several bacterial diseases that can cause this. I can’t say which your issue might be, but if it persists or gets worst, you might be able to bring in a sample somewhere to have it analyzed. In the US, I’d bring it to a County Extension agent, but I don’t know what the Canadian equivalent would be.
what is the biggest variety of Jchokes or is the size dependent upon how they are raised?
Hi Bill, I forage for my jchokes so I don’t know what variety they are. I grew some in a corner of my garden for a few years but jchokes do not know the meaning of the word “boundary” so they had to be eaten! I got those chokes from a friend, who had foraged them, so again, no thoughts on the size of different varieties. I can tell you that the shape is definitely influenced by growing conditions, specifically how much water they get and what the soil is like. That might also influence their size.
Size of tubers and yields depends on amount of sun. They prefer full sun throughout the entire day. Soil conditions – they will grow quite well in most any soil except wet, they can rot like potatoes. One very wet summer gave me a slew of worthless pithy ‘chokes. They of course do better in loose loamy soil, best in fresh garden compost. They tolerate some drought, but the tuber growth needs some water occasionally from late August all through their flowering. Waiting to harvest until the tops have died and fully dried allows the nutrients to drain into the tubers giving them their best size and flavor. You’ll hear ‘after the first frost’. No. My reds are a late maturing variety and they tolerate being hit by all but deep killing frosts of below 28F, even the flowers won’t wilt unless there’s a very hard frost. Harvest too early and they can be bitter. I have experience with three varieties. The best producer is one I assume to be Stampede. They are a white/tan skinned very knobby tuber that only spreads about 16″ from the crown under a 5′ to 6′ top. That spread makes them easy to keep contained by regularly mowing a swath around the patch at least 24″. In that 16″ spread they grow quite dense. Out of a patch that’s about 15 years old and 5′ x 25′ I easily get 30 gallons just by pulling the stalks, then when I go after them with the sod fork I can get around 50 gallons and still miss more than enough for next year’s crop. The next one is a red skinned smooth tuber about 5″ long x 1 1/2″ thick at their best, most are smaller. Picture small sweet potatoes. They spread a good 24″ under an 8′ top and don’t grow nearly as dense. I’d be lucky to get close to half the amount of these as the Stampede. I need to mow a border 3′ wide to keep the patch contained. The Stampede(?) have an earthy, sunflower seed flavor. The reds have a more pronounced nutty flavor.
I had another. It spread over 4′ from the crown and was a bear to keep from spreading out of control. They needed a mown border of at least 6’+ just to be safe. It had white/tan skinned smooth tubers shaped like the reds but they had an obnoxiously strong herbal turnipy flavor. One tuber chunked into a pot of soup or stew was more than enough to flavor the whole pot and they stunk up the kitchen too! They also grew 12’+ tall. They were nasty and I got rid of them. You’d think that with an 8′ diameter spread there’d be a slew of tubers, not so. They didn’t produce much more than the reds.
There are those who say that early deadheading of the flowers will increase yield. Meh. I tried it on one half of one patch one year and there was not one bit of difference between the sides. I will say I made a large batch of flower broth wine and that was superb! The simmered flowers tasted a lot like squash and went down well with a dab of butter! And every part of the plant is edible. The leaves have a hairy texture that disappears after 5 minutes of cooking. My reds have leaves three times the size of my hands and make a good Mediterranean wrap like grape leaves, very tender after cooked.