Crops

The Real Reason Root Crops Never Show Up in a Vertical Farm

Say you are putting together the business plan for a vertical farm, filling in the column for which crops to grow. Lettuce, baby leaf, herbs — once you write them out, the list is all leafy greens. Then your boss says, “See if we can add daikon and carrots too — look into it.” You run a search to check, and you notice something. Hunt as you may for vertical farm cases, root crops barely come up.

It is not that they cannot be grown. Technically, root crops grow in a plant factory just fine. And yet they almost never reach the market. The reason lies somewhere other than whether they can be grown.

Root crops are missing not for lack of technology but as a verdict of the margin

Potatoes at the local supermarket: three to a bag for 100 yen. Set them next to vertical-farm lettuce selling at 200 yen a head, and root crops simply do not pencil out. On top of that, root crops take time to grow, and they fatten underground, so there is little point in stacking shelves several tiers high. The question worth sitting with is whether this is a story of “the technology hasn’t caught up yet,” or one where root crops are rejected from the start as “not worth doing.”

Here is the thing: that figure, 100 yen, already tells most of the answer. Most of a vertical farm’s cost tracks area and time. Lighting and HVAC are like rent charged in proportion to how long you tie up a stretch of shelf area, and what matters is “how many days you occupy that area, and how much harvest comes out the other end.” Lettuce is short, light, and turns over in about 30 days. Root crops take months to fatten, and for their weight and volume their unit price is low. Occupy the same area for the same number of days, and root crops come out several times worse than lettuce on the math.

So it is not a story of the technology failing to catch up. Closer to the truth is that they drop out at the spreadsheet stage. The fact that they fatten underground and so resist stacking does matter, but before that, root crops are turned away at the door on “how much do you earn per area per day.” Put the other way: only crops with a high unit price, light weight, and fast turnover can ride those shelves.

The “rent” analogy is quite close to reality. The whole time a shelf area is occupied, it keeps eating electricity for lighting and HVAC. A vertical farm’s cost is driven mainly by the electricity bill — lighting and HVAC — and at today’s power prices it has been reported to lose to an ordinary field on cost efficiency (ref: 1, 2). What is more, even among covered cultivation, a vertical farm carries far heavier energy per unit yield than a greenhouse. Where a greenhouse runs roughly 27 megajoules per kg, a vertical farm runs 78 — nearly three times the electricity to take the same amount, and that gap has not narrowed from 1993 to 2024 (ref: 2). The same analysis states by name that, grains aside, root crops too do not stand up under closed-environment production at today’s costs. It is tempting to wait for “technology to make it cheaper someday,” but the industry-wide trend of getting cheaper at scale is, in the data, almost nowhere to be seen. So “it tracks area and time” is not a metaphor but an actual structure that makes up a large share of the cost. On top of that ride the per-crop coefficients — marketable rate, labor, sales channels — if you want to be precise.

What decides the margin is unit price, turnover, and space occupancy

Turn it around, and as long as the price per area per day is high enough, even a root crop can ride the shelf. Not ordinary daikon and carrots, but root crops that sell for a great deal — something like medicinal ginseng, or crops carrying added value — can make the math work in some cases. Unit price and turnover act separately, and what wraps both into a single expression is “price per area per day.” Things with an extreme unit price like medicinal ginseng or wasabi turn up as cases in both soil cultivation and closed environments. Baby carrots are cheap because they earn turnover through early harvest — less about added value, more about settling the account through time.

So is it the low unit price, or the slow growth and poor turnover? Root crops, as bad luck would have it, lose on both. The unit price is low, and on top of that they take time to fatten, so turnover is poor too. Unit price and turnover don’t work one at a time — both bear down as a multiplication. The one difference is that unit price can be raised by searching — you find a variety or use that sells for more — whereas the time it takes a root to fatten is the plant’s own affair, hard to shorten with money. The occupancy days, being hard to trim through on-site ingenuity, are root crops’ real weight.

Let me put the actual day counts in here. Leafy greens like lettuce turn over in roughly 30 to 40 days, by shop-floor reckoning. Carrots, on the other hand, you need to allow about 70 to 120 days from seeding to harvest. The real number to put in the denominator is this one. The same area, tied up for one month in one case and three to four months in the other. From this alone you can get a rough sense of how far apart the “per area per day” figures fall.

The area at which the math works differs completely by crop. Lettuce, under advanced cultivation technology and favorable price conditions, has a minimum scale where the math works that fits within a tiny 17 to 38 square meters. But try strawberries in the same facility and the break-even line leaps up past 16,000 to 115,000 square meters. With the very same vertical farm technology, just change the crop and the scale at which it works shifts by orders of magnitude. What pushes this order-of-magnitude gap wider still is occupancy time. Lettuce clears the shelf in about a month, while root crops tie it up for months. The longer the same area is occupied, the larger the denominator swells, and the further off the workable scale recedes — which is exactly why long-cycle crops like grains and root crops are named as failing to stand up in a closed environment at today’s costs (ref: 2).

There is a yield multiplier often trotted out: “a vertical farm takes dozens of times more per area than the open field.” That is a story for crops like lettuce that can be stacked high in tiers, and one estimate puts ten tiers at 100 to 200 times the open field (ref: 4). But that multiplier does not, by itself, mean victory on margin. Taking a lot does not guarantee the investment is recovered — that how much you take and how much you earn are different stories is something the per-crop margin analyses show plainly (ref: 3).

Before the margin, the root itself does not fit the equipment

Up to here the story has been “they drop out on margin.” But stand on the floor and you run into a wall one step earlier. The root of a root crop simply does not physically fit today’s vertical farm equipment.

In a root crop, the part you eat is itself a root that swells. Carrots and daikon are taproot crops, sending a thick root straight down deep into the ground. Supporting that growth takes a soft growing medium with enough depth and breadth. But the equipment that dominates existing vertical farms is optimized for leafy greens — thin floating rafts and circulating nutrient solution, a design philosophy built with leafy greens in mind. It is hard to secure either depth of medium or supporting strength. On top of that, when the root zone is filled with liquid, oxygen supply to the roots tends to fall short. Lacking both the space for the root to fatten and the medium’s physical strength to hold the root, growing root crops at all is difficult with current equipment as it stands. This is not an armchair argument; it is a fit problem you grasp the moment you stand in front of the equipment.

A word of caution about the order here. Margin first, or physics first — that flips depending on where you, the reader, stand. If you are in the position of designing a new line from scratch, the division on margin drops root crops first, so you never get as far as the equipment discussion. If, on the other hand, you already own leafy-greens equipment and are thinking “root crops on the empty shelves too,” then before margin even comes up, the root will not fit the equipment and is physically struck from the options. Which wall is the main cause changes with where you are standing.

If you absolutely must grow root crops in a vertical farm, the types where the nutrient solution does not circulate — the two methods of fertigation and aeroponics — can handle it. Fertigation puts soil in a container to the depth the root needs to grow and supplies nutrient solution by drip. Because it lets the taproot extend in soil as it naturally would, it is close to the root crop’s natural growth. Aeroponics sprays a fine mist of droplets tens of micrometers across directly onto the roots, delivering ample oxygen along with water and nutrients. But both are nothing like the circulating leafy-greens line you picture when you hear “vertical farm.” My honest conclusion from the floor is the obvious one: it is reasonable to grow root crops in soil.

The first thing you write is not a crop schedule but a one-line division

So how do you check that margin in your own hands? Before you look into whether something can be grown, there is something you should write on the first page. It is not a crop schedule — a one-line division is enough. On paper or in a cell, take the same shelf area as your baseline and work out “assumed sale price / occupancy days.” Put lettuce as the baseline, and line up the candidate root crops on the same area conditions in the same table. That alone settles most of it.

The order goes like this. First, set down one price at which the candidate sells. Next, set down how much area and how many days from seeding to harvest that crop ties up the shelf — 30 to 40 days for lettuce, 70 to 120 for carrots, those real numbers. Root crops, whose underground part is bulky and hard to pack into a single tier, are already at a disadvantage right here at occupancy. Divide the price by occupied area and days to get “sale price per area per day,” and compare it with lettuce’s figure. If the order of magnitude differs here, looking into whether it can be grown is wasted effort, so stop there. Pinning down whether it can be grown and the yield rate is only for candidates that pass this division. Reverse the order, and you take the most wasteful detour of all: arriving at the conclusion “it can be grown” and then dropping out on margin.

This division is a rough cutoff for dropping candidates, not the precise margin itself. What you write on the first page is the crop’s name and price, occupied area, occupancy days, and that division. Coefficients like marketable rate, grade-pass rate, labor, and sales channels go on from the second page onward. The first page is a sheet for persuasion and for cutting.

This “if the order of magnitude differs, stop before looking into cultivation” cut shows up at its most extreme with staple grains. Rice, wheat, and corn make up 60 percent of the world’s food energy, but reviews and critical analyses agree in pointing out that cultivation in a closed environment will not be economically viable for the foreseeable future (ref: 5, 6). There is a telling estimate. Even in the best-case scenario of growing wheat in a Swedish vertical farm, electricity alone runs to the equivalent of 40,000 dollars per ton — roughly 100 times the world wheat price at the time (ref: 6). It is the clearest example of all that this is not a problem of cultivation technology, but a contest that is over at the division stage. The same logic applies, if less extremely than for grains, straight to low-priced root crops too. Eyeing the order of magnitude with a one-line estimate is the move for catching this kind of “not worth looking into” early.

Telling “it could be grown” apart from “the margin passed”

Have you ever read an article saying “a root-crop vertical farm succeeded overseas,” or heard that a lab managed to harvest potatoes, and gotten your hopes up — “so root crops can work after all?” But whether that is a case that passed the margin division, or merely a story of “it could be grown,” is meaningless unless you tell them apart. When you see an article, the first thing to look for is whether it states “how much it earned per area per day.” If it does not, it is usually just a story of it being grown.

The markers for telling them apart are points like the following. Are both price and occupancy days stated? Anything with only “it could be harvested” or “we took so many tons,” with no mention of how many days it tied up the shelf or what it sold for, stops at the technology story. Do the words “subsidy” or “public support” appear — here is where “success” splits between margin and money simply flowing in from outside to keep things running. And what is that root crop? If it is something with an inherently off-the-charts unit price like medicinal ginseng or wasabi, it can hold up as an exception that passed the division.

There is a trap here, though. Even when one variety holds up as an exception, it only passed because it met the condition “high unit price” — the weight of the time it takes a root to fatten has not disappeared. It is not a story you can extend straight to daikon, carrots, or potatoes. Whether there is real promise, you judge by reading all the way to “which root crop passed, on what numbers,” and whether that condition also holds for your own crop. The more an article hides the crop name and just writes “root crop succeeds,” the more you are right to come at it with suspicion.

And the conditions that line up when an exception holds are not unit price alone. By the feel of the floor, (1) there is dedicated equipment matched to the root crop’s growth characteristics, (2) a sales strategy for a high-value-added product to match it is in place, and (3) it can win against the competition from other high-unit-price crops — only when these three line up does it ride the shelf. It is not a story where, just because the unit price is high, you can load root crops straight onto an existing leafy-greens line.

The expectation that “technology will catch up and make it cheaper someday” is the easiest place to miss. The wall of vertical farming’s high capital cost has been pointed out as structural rather than a temporary lag in technology. The 1960s tower greenhouses, the various attempts of the 1980s — the same “we can save land” story was repeated each time, and each time it fell short of the margin (ref: 6). Among the reasons adoption has not advanced, on the wall of consumer acceptance, multiple surveys show that attitudes are still divided (ref: 7, 8). The very posture of waiting for technology is the detour that reverses the order.

The way to tell exceptions apart has backing too. Aeroponics often comes up with potatoes, but what is being used is not the mass production of edible tubers — it is the use of multiplying seed potatoes (minitubers). In fact, research has reported obtaining high-quality seed potatoes on aeroponic-type equipment (ref: 9). Seed stock is high in unit price and low in volume — in other words, it is an exception that passed right through the entrance of the margin, in the gap where “price per area per day” holds up. That this is a different arena from mass-producing edible daikon and carrots is, here too, clear once you look at “for what use, on what numbers, it passed.”

Put the first page of the margin before the technology

By the time you get here, you can see that the framing you first got hung up on — “has the technology not caught up?” — had the order backward to begin with. You can’t help worrying first about whether it can be grown. But really, you write the one line “assumed sale price / occupancy days” first, drop from the candidates anything that looks poor next to lettuce — and only what passes that division do you look into growing. As long as the weight of the time it takes a root to fatten does not disappear, what you should look at, before technology, is that first page of paper. That’s the case if you’re designing a new line; and if you have existing equipment, don’t forget the order here either: before margin even enters, the physical wall — whether the root fits the equipment — stands in the way.

Just swap the order, and most of the hesitation disappears. The technology story is interesting, and what it can do grows year by year. But that is a story that comes alive among the crops that have passed the entrance of margin; place it before the entrance and it becomes a detour. Root crops are missing not because the technology lost, but because they are quietly cut at the entrance. Once you can see it that way, the next time a new crop appears, you can start, without panic, from that first page of paper.