Crops
Why Root Crops Are Rarely Grown in Vertical Farms: Compatibility with Hydroponics
You see vertical farms for lettuce, but you almost never see vertical farms for daikon radish or carrots. It is not that the demand is missing. It is that the growth characteristics of root crops and the existing equipment do not match.
With root crops, the edible part is the root itself, which swells as it grows. They need depth, physical support, oxygen supply, and ease of handling at harvest. That is a different design philosophy from a leafy-greens line built around shallow grow panels and a recirculating nutrient solution system.
In this article, I lay out why root crops are difficult under hydroponics, which cultivation methods do have potential, and the economic reasons why they are rarely chosen as a business.
I have also written about why vertical farms lean so heavily toward leafy greens in the article below.
The “Why” of Vertical Farms: Why the Crops Became Almost Entirely Leafy Greens
The Challenges of Growing Root Crops in a Vertical Farm
Root crops are vegetables such as carrots, daikon radish, and burdock, where the root portion grows thick and that swollen root is what we eat. A defining feature is their taproot structure: they form a single thick root that grows straight down deep into the soil. To support that growth, you need loose, deep soil with enough space in all directions.
The equipment that dominates today’s vertical farms is optimized for leafy greens, and its structure makes it difficult to provide the depth and space of growing medium that root crops require. On top of that, when the root zone is filled with liquid, oxygen supply to the roots tends to fall short. Both the space the roots need to grow large and the physical support the medium has to give them are missing. With today’s standard equipment, root crops are simply hard to grow.
Cultivation Methods Suited to Root Crops in a Vertical Farm
To get straight to the point: it is more rational to grow root crops in soil. If you insist on growing them in a vertical farm, two methods can work: soil-based fertigation, and aeroponics. Both differ from the common image of a “vertical farm” in that they do not rely on the shallow, continuously recirculating nutrient-solution beds used for leafy greens.
Soil-based fertigation means filling deep containers such as grow bags with soil to the depth the roots require, and supplying the nutrient solution through drip tubes or similar systems. The roots can grow in the soil as taproots in their natural form, which suits how root crops develop.
Aeroponics is a form of hydroponics in which a mist of nutrient solution is applied directly to the roots. The mist particles are as small as a few tens of micrometers, so together with water and nutrients the roots also receive plenty of oxygen. That makes it a technique that could become a new option for root-crop cultivation.
With these two methods, you can secure the root-zone volume, substrate depth, and oxygen supply that root crops need, while managing the nutrient solution to deliver what the roots need to swell.
The Problem: It Simply Does Not Turn a Profit
Just as important as the technical challenges, and perhaps more so, is the economic problem. Growing root crops in a vertical farm is not technically impossible, but the reality is that the numbers do not add up.
Root crops have longer growth cycles than leafy greens, and their crop turns (how many harvest cycles you can run in a given period) are low. In a vertical farm, output per unit time translates directly into revenue, so this gap is fatal. Lettuce and other leafy greens can be harvested in roughly 30–40 days, whereas carrots take about 70–120 days from seeding to harvest. In a vertical farm, where fixed costs are high, few crop turns translate directly into low profitability.
As long as you are running a vertical farm as a business, there is no reason to deliberately pick a crop that does not earn. Root crops not being chosen is a perfectly natural outcome.
From both the cultivation-technology side and the economic side, the range of vegetables a vertical farm can realistically grow is limited. The same issue applies to grains.
The Future Prospects of Root-Crop Cultivation in Vertical Farms
As things stand, root crops will not be chosen for conventional hydroponic equipment. But this does not mean the situation will never change.
The fundamental reason root crops are not chosen is that existing equipment does not accommodate their growth characteristics. If cultivation equipment specialized for the growth characteristics of root crops is developed, and a matching sales strategy for high-value-added products is established, the situation can change.
However, even if those conditions come together, a vertical farm is always competing with other high-unit-price crops. For root crops to be chosen, they have to clear both technical and business hurdles, and then show a clear advantage over other strong candidates. That path has not yet emerged. That is where we stand today.