Romaine lettuce is known for its long, crisp leaves that form a tall head. It is typically grown in the cooler months in fields, using traditional farming methods such as tillage, planting, irrigation, fertilization, and pest management. The lettuce is usually harvested by cutting the entire head off at the base, then transported to a processing facility for washing, packaging, and distribution. Some farmers may also use greenhouse production methods, where the lettuce is grown in a controlled environment, which can allow for year-round production and can be used to protect the plants from pests and extreme weather conditions. In recent years, the use of hydroponics systems has also become more popular for lettuce production, which involves growing plants in nutrient-rich water rather than soil.
Total Lettuce Market
The Food and Agriculture Organization of the United Nations (UN FAO) provides global statistics for lettuce and chicory production. Romaine is a dominant variety of lettuce, but it’s important to realize that the actual romaine markets are a subset of the provided statistics below. Toward the second half of this section, we’ll provide some US-centric data from the USDA National Agricultural Statistics Service (NASS) that isolates romaine production.
Global Lettuce and Chicory Market
The global lettuce and chicory market can be addressed in terms of total production (tons) and as the total value of production (USD.) China is the top lettuce and chicory producing country, producing approximately five times more lettuce than the US, which is the second largest producer. Other notable production regions include India, Spain, Italy, Japan, Belgium, Turkey, Mexico and France. Its interesting to note that Belgium is by far the most efficient production region, and that India, while producing substantial tonnage, has a very low yield per hectare of productive acreage. In theory, it is possible for Indian production to increase five- to six- fold without impacting productive hectarage by increasing yield.
TABLE 1: Global production of lettuce and chicory (FAOSTAT)
2021 Production by Tons
2020 production by tons
2020** Production by Estimated Value ($1000)
Yield measured by hg/ha
**The most recent available global Lettuce and Chicory GDP data from FAO is in 2020, which doesn’t line up exactly with the most recent acreage report (2021), but it is close.
CHART 1: Production Share of Lettuce and Chicory by Global Regions in 2021 (FAOSTAT)
Domestic (US) Romaine Market
The USDA NASS breaks the US lettuce market into three primary segments: head, leaf, and romaine lettuce. In the below report we have isolated the romaine lettuce datasets for California and Arizona, which, when combined, account for ~ are the dominant romaine production regions. (As is evident in the table below, the USDA NASS statistics exclude romaine production from the other 48 states in the US figures, making this informational useful for general guidance as opposed to anything conclusive.)
TABLE 2: Harvested acres and utilized production of romaine lettuce in the US for 2020 and 2021 (USDA NASS)
Utilized Production (1,000 cwt)
Production measured in $US
In total, according to “Research and Markets”
- The US Lettuce and Chicory Market was estimated to be valued at $4.59 Billion in 2022.
- The compound annual growth rate of the US Lettuce and Chicory Market is 2.6%, with an estimated value of $5.09 Billion by 2026.
- Like most fresh commodities, the price point for romaine lettuce varies seasonally and with weather and shipping variables.
- To illustrate the above - according to the National Agricultural Statistics Service (NASS), the October free on board (FOB) shipping-point price for iceberg lettuce averaged $126.00 per hundredweight, up 150% from September 2022 and 132% above the average of the past three years. The net effect of limited supplies, wide-ranging quality and sizing, and elevated prices as the desert season moved into December. By mid-December, after the chaotic start to the desert winter season passed, supplies of leafy and cruciferous vegetables slowly improved and prices began to ease, although remaining well above the average of the past three years.
TABLE 3 - US Fresh-market Organice And Conventional Vegetable FOB Prices Per Pound 2021-22
As one of the most economically important leafy vegetable crops in the world, it is increasingly important to understand lettuce from both a domestic and a global perspective.
“Based on most recent production and price averages in the US, the estimated gross value per acre is approximately $10,400 for head lettuce. The cost of lettuce production varies depending on the location. It is labor-intensive, especially for harvest and post-harvest handling and packaging.” [Source]
The total addressable market for Romaine Lettuce is an important upperbound constraint to be aware of when analyzing the market opportunity that a technical solution provider has when marketing to romaine producers. Understanding the realistic addressable market for specific technology applications (i.e., harvest automation, precision fertigation, precision irrigation, etc.) is equally critical, as it enables solutions providers to realistically determine appropriate sales pricing and costs of goods constraints. Knowing the total production of romaine lettuce and the GDP of said production on a global and geographic basis can help investors make informed decisions about where to invest, as well as inform strategic decisions about where to enter the market.
Planting and cultivating romaine lettuce is a heavily mechanized process that relies upon a direct seeder or transplanter. Typically, the equipment is attached to a tractor that is driven across beds. However, how a farmer chooses to plant the lettuce is ultimately a choice that is driven by the unique factors of their given soil and farmland.
Romaine lettuce is a valuable and important crop in the United States, but growing it is not without its challenges. Farmers must consider the environmental and seasonal conditions, such as temperature, drought, and pests, and consider the cost of production, labor, and post-harvest handling when developing their crop plans.
Typically, romaine lettuce takes anywhere from 65 to 95 days from planting to harvest depending on genetics, weather, temperature, humidity, soil types, seed depth, stimulants, endosperm thickness, and more.
Romaine lettuce—unlike its younger family member baby greens—is still hand harvested and packed in the field. The prioritization of quality control has meant that there is yet to be a machine that can out-pick a skilled picker in the field.
John Mckeon from Earthbound Farms describes the harvest and packing process as “a labor-intensive process, which is done from a harvest machine. It is from this central hub that crews (usually made up of 25-35 people) harvest and pack the romaine. Product is cut from the field by harvesters and placed on the first tier of the harvest machine.”
Sample Costs to Produce and Harvest Romaine Hearts:
Understanding the costs and market conditions associated with producing romaine lettuce is important to growers so that they can maximize the value of the crop and ensure a successful harvest. Additionally, growers must be aware of the pest and disease control methods they can use to protect their crop and ensure a good harvest. This UC Davis research study, can be used to make production decisions, determine potential returns, prepare budgets and evaluate production loans. The practices described are based on production procedures considered typical for this crop and area, but they will not apply to every situation.
These production costs are critical for startup founders to understand because this information will help to set realistic targets for the product development. Understanding that “harvest costs” make up ~46% of total operating costs per acre enables a harvest automation startup to more realistically isolate the market value of their product and acknowledge that there likely is a willingness for most romaine growers to invest substantial (though not un-capped) operating capital in harvesting solutions.
In short, crop budgets detail the various practices involved in producing romaine lettuce, which can be summarized as follows. Land preparation, which includes discing, subsoiling, compost application, and bed cultivation, begins in October/November of the year prior to planting. The lettuce is direct-seeded using a precision air planter, and thinned to a 9-inch in-row spacing using an automated thinner. In addition to compost, fertilizer such as potassium sulfate, nitrogen, and liquid fertilizer are applied at the discretion of the farmer. Irrigation involves applying 4 acre-inches of water through sprinklers during stand establishment and 10 acre-inches through the drip system for the growing season. Pest management involves monitoring for insects and diseases and applying three to four pest management applications. Weeds are managed using herbicides and hand weeding.
Post Harvest Handling:
Lettuce is a cool-season crop that grows best with moderate daytime temperatures of 73 degrees F and cool nights of 45 degrees F. After harvesting, lettuce should be cooled immediately in order to maintain its freshness. One method for cooling is through vacuum cooling, which brings the temperature down to 34ºF (1ºC), Product is then stored at just above freezing with 98% relative humidity. Lettuce that has been harvested at its prime maturity without any defects can be held for two to three weeks at 34ºF (1ºC). However, if stored at 37ºF (2ºC), the shelf life will be reduced to one to two weeks. There are also specific storage disorders that can affect lettuce such as russet spotting, caused by exposure to ethylene gas, and brown stain, caused by high levels of carbon dioxide in the storage area. [Source]
Because proper temperature maintenance is key to increasing shelf life and preventing storage disorders, lettuce can be an incredibly difficult specialty crop to handle post harvest.
It is critical to understand, at least at a high level, the various horticultural practices that are required to produce romaine lettuce. These practices affect product design and development efforts, and understanding them helps to provide a fuller picture of the harvest and harvest-related activities. The following activities should be looked at to help maximize the impact of harvest automation.
One common offering is a consumer package containing three romaine “hearts.” For this product, heads are harvested by hand in the field using a knife. Harvesting lettuce by hand is important to ensure that the heads are gathered at the optimal maturity and size. Hand harvesting also allows for greater control over the size and quality of the heads harvested, at least at present (June 2023) and reduces the likelihood of crop damage relative to that with mechanical harvesting. Additionally, hand harvesting can help to reduce waste, as workers can pick out any damaged or unmarketable heads. Finally, hand harvesting is generally the most cost-effective harvesting method available today for smaller crops. [Source]
The D’Arrigo Brothers’s Youtube channel features a series of very useful videos documenting lettuce harvest.
In the video below, publsihed in March 2021, one can get a sense of what fully manual romaine heart harvesting looks like.
Today, it is generally true that:
- Lettuce is produced year-round and is ready to harvest after 60-90 days, depending on the season and weather.
- Growers plant lettuce each week to ensure a constant supply, and two or three crops can be harvested each year from one piece of land in the Salinas area.
- Mechanical thinners and weeders have reduced the need for pre-harvest hand workers. The harvesting method depends on the type of lettuce and its usage.
- Romaine lettuce is typically harvested by crews of 20-26 workers who walk behind conveyor belts to select and trim mature heads before placing them in cartons. 80% of head lettuce is mature during the first harvest and can be harvested a second time if prices justify.
- Machines are also starting to be be used for harvesting baby leaf lettuces and immature romaine lettuces (note that this is for young leaves, not for romaine hearts.) [Source]
The video below displays some of the different machine and robotic technologies that D’Arrigo Bros are using and testing in their romaine fields.
Lettuce Harvester Requirements and Lessons Learned According to VP of Ag Ops at Major Lettuce Farm Operation
- An automated harvesting machine/platform that can select and cut, the correct lettuce heads, based on given selection criteria. (Quality criteria needs to be broken out into Fresh Market Lettuce and/or Processed Lettuce.)
- Adjustable criteria for good versus bad heads that is adjusted on the fly, so that the machine/platform can be told what to do in real time.
- A machine/platform that can move through the field at, or better than, the current pace. A machine needs to either cut the same number of rows as today’s machines, at the same pace as todays machines, or it must cut fewer rows at a much faster pace in order to produce the same numbers of usable heads as the current machines/crews.
- A “header” - the part of the machine that cuts the lettuce -that can select and cut heads that are high quality (in other words, it needs to be able to exclude damaged heads.) This can be done by selecting just the heads that meet the criteria given, or by cutting all the heads at one time, and removing the heads that do not meet the criteria later.
- A machine/platform that’s small enough to both maneuver through and around fields and can be easily transported from one location to another.
- A machine/platform that’s able to operate in different weather and soil conditions, including but not limited to, wind, rain, mud, etc.
- A machine/platform that has sorting/cleaning/trimming capabilities, either with an area where this can be done manually, or automatically.
- A machine/platform, that has the ability to load the lettuce after cutting and sorting, onto another platform for transportation to a facility.
- A machine/platform that can be worked on, or repaired, by in-house employees, or remotely through the internet by people outside of the company.
- A machine/platform that fits the current planting/cultivating standards, or fit a new standard that is both practical and economical.
Lessons Learned (using currently available machines)
- “Header” - needs to be able to cut luttuce at a pace that is equal to, or faster than the current method, which is hand harvest with a crew, and with the same quality standards.
- High Pressure Water Knife – While this method does a nice job of making a clean, sanitized cut, it is slow in order to avoid splashing the soil up onto the plant, as well as to give the water enough time to cut the head. If you go fast with this method, the water will not be able to cut effectively.
- Band Saw – This is an effective method, but there are issues with speed. With the band saw, if the forward movement is too fast, there can be cutting issues, because the movement ends up pushing the heads forward faster than they are being cut. Also, this type of blade, can cause excessive damage to head, which can result in crop loss.
- Large Circular Blades – This method did not work. Heads were cut in half and thrown around. Not only is it hard to cut all the heads at the same level with this type of system, it also creates a lot of friction on the cut surface of the lettuce, which can result in damage and crop loss.
- Rubber Bands or Belts/Digger – This method works by grabbing the root, or core stock below the head, and taking the head out of the ground, without an initial cut. This works well for forward speed, and allows for a precision cut after being removed from the ground. However, this method comes with a lot of dirt issues, and second and third cutting needs, which means a longer header, or other steps.
- Robotic Arms – This method works, but speed becomes an issue as well as how do the robotics hold up to the elements. Robotic arms can move quickly, but it’s still unclear if they can do that while to cutting and handling the head. There has not been enough testing of this method yet, in my opinion, to know enough of the possible pit falls.
- Machine size needs to be reasonable, in order to fit into, and around fields. Current machines are generally very easy to move through and around the fields, as well as down the road to other field locations.
- Most often, field are small and irregularly shaped, which makes it difficult to move a large machine through.
- At the end of the rows, or harvest passes, the machine must turn around to go down the next “pass” on a “field road” which is typically 10’-15’ wide.
- When the machine moves through the field, there will likely be spots where the field is wet, and so the lighter the machine the easier it is to navigate these field challenges.
- Overall technology package needs to be reasonable. The machine can’t become too complicated to operate, and to fix.
- The technology has to be used by the current field staff, which presents a problem. It is one thing to teach the field staff how to operate the machine, but it is a problem when they have to be able to write code, or setup a complicated computer system to run the machine.
- Likewise, if it takes a specialized computer programmer to adjust the machine, it makes it difficult to have real time adjustments. Currently, most field staff or mechanics in the Lettuce business are used to working with nuts and bolts, as well as air or hydraulics, but not computers.
- If programing is going to be a part of the operating or adjustments, then it would need be either a local person, or done remotely. These both have been an issue in the past, not having the correct person “locally”, and not being able to connect the machine to the internet in the field, due to lack of connectivity in that location. Which then forced the operator to move the machine back to a central shop location, and stop working.
Machines To Harvest Romaine -
Ramsay Highlander has launched a new product called the Mechanical Harvester that is designed to harvest Romaine, Green Leaf, Iceberg and other commodities. The harvester utilizes Ramsay’s patented Water Jet cutting method which increases yield and product shelf life while increasing labor efficiency. It has an individual high-pressure water stream for every seed line, allowing for independent adjustment of cut height for uneven beds. The harvester also helps eliminate trash leaves before reaching the sorting/packing belt and can be configured for totes or bins. The harvester can harvest 12,000 pounds of Romaine per hour into totes and up to 24,000 per hour in a bulk loading version. This harvesting method is considered the way of the future due to its increased yield, natural sanitary cutting method and ability to negotiate uneven beds with less water consumption. [Source]
Considerations For Automation
The UC Davis Cost Study done in 2019 and referenced above goes into more detail about the labor costs for producing Romaine Hearts on the Central Coast of California. The hourly wages for machine operators, irrigators and general labor in 2019 were $24.70, $20.80, and $18.70, respectively. The cost includes the employers' share of taxes, workers' compensation insurance, and other benefits. The state minimum wage and overtime regulations may result in increased labor costs. Growers can also use the H-2A guest worker visa program, but it may result in higher labor costs. Interest on operating capital is calculated monthly until harvest at a nominal rate of 6.25% per year. Equipment operating costs include fuel and lubrication, repair, and pickup truck costs. The risks of producing and marketing the crop are high, and the study cannot fully represent all the risks involved.
Mechanized crop production is becoming more common in the global agricultural industry as labor becomes scarce and more expensive. This includes lettuce production, with growers looking for new varieties that can be harvested by machine. The American fresh food industry is very dependent on agricultural laborers, but fewer immigrants are arriving in the US to take on agricultural jobs and agricultural laborers are becoming older. This development places immense pressure on growers to find innovative solutions. This is a global problem and the global aging of the farming population is increasing the need for new advanced technologies. [source]
A crew of 10 cutters and 16 packers, stackers, and drivers can harvest 2,500 to 3,000 cartons of romaine lettuce in an eight hour day. Growers guarantee all members of the crew receive minimum wage (with many harvesters often receiving much more), and offer a bonus that is shared by the crew if they harvest more than a target level of cartons, which varies by field and yield. Crew-bonus systems allow most lettuce harvesters to earn several dollars an hour more than California’s $15 an hour minimum wage, often $150 or more a day rather than the $120 guaranteed by the minimum wage.
Incorporating a hygienic design for automation of lettuce is also an important consideration.
Considerations For Pests, Disease, And Weather
Pests and Diseases that affect the lettuce
- Soil-borne pathogens (such as Pythium Wilt) can infect romaine lettuce through the roots, causing wilting, stunting, and death of the plants. These pathogens thrive in warm and wet soil conditions, making them more prevalent during certain seasons and in certain regions. Proper crop rotation, sanitation, and use of disease-resistant varieties can help to control the spread of Pythium wilt.
- And Thrip-vectored Impatiens Necrotic Spot Virus (INSV) is a viral pathogen that is transmitted by thrips, tiny insects that feed on plant sap. When thrips feed on infected plants, they acquire the virus and can then transmit it to healthy plants when they feed. Symptoms of INSV include leaf necrosis, leaf curling, and stunting. Control measures include monitoring for thrips populations, using thrips-resistant varieties, and using pesticides to control thrips populations.
- Both of these pathogens can have significant effects on romaine lettuce yields and can lead to significant crop losses if not properly managed.
Lettuce crops, including romaine lettuce, are highly susceptible to damage caused by weather conditions. Although lettuce can grow in a range of temperatures, extreme heat or cold can cause significant damage to crops, affecting both their growth and yield. Strong winds, heavy rain, and hail can also damage lettuce crops, leading to a reduction in their overall yield. Additionally, soil moisture levels need to be carefully monitored, as both too much and too little water can negatively affect lettuce growth.
Heavy rainfall can cause soil erosion, leading to the loss of nutrients and the degradation of soil quality. Furthermore, excessive soil moisture can promote the growth of fungal diseases that can damage crops. Conversely, drought-like conditions can cause lettuce crops to wilt and become stunted, leading to lower yields.
Growers consider weather patterns and conditions when planning their planting and harvesting schedules. In areas where rainfall is scarce, irrigation techniques can be used to supplement the water supply and maintain soil moisture levels. In regions that experience heavy rainfall, growers may need to implement drainage systems to prevent soil erosion and control water levels.
Overall, managing weather conditions is a critical aspect of lettuce production, and growers must take measures to protect their crops from adverse weather events. By monitoring weather patterns and implementing appropriate measures to maintain soil moisture levels and protect crops from damage, growers can maintain high yields and produce high-quality lettuce crops that meet consumer demand.
Considerations For Food Safety
Food Safety Is Complicated:
Growers must implement strict protocols to prevent contamination and ensure food safety, such as regular testing and monitoring of soil and water sources, implementing food safety measures during harvesting and packaging, and complying with government regulations. These measures can be expensive and time-consuming, particularly for small-scale farmers.
At the same time, food safety is of utmost importance as it directly impacts consumers’ health and well-being. The risk of foodborne illness is a serious concern, and consumers have the right to expect that the food they purchase and consume is safe. With recent outbreaks of E. coli and other pathogens in romaine lettuce, consumers have become increasingly aware of the need for rigorous food safety protocols. In order to maintain consumer trust, it is important that all farmers and members of the food value chain, regardless of size, take food safety seriously and implement best practices to prevent contamination.
Compliance with government standards and regulations is important to ensure that all farmers are held to the same standard, and to prevent outbreaks of foodborne illness. Compliance with these regulations can be painful and costly for farms, creating tension.
Hygience is a top-of-mind issue not only on farm, but throughout the supply chain for lettuce and leafy greens, from farm inputs to retail.
CDC has a very informative page on food safety communication specifically targeted towards leafy greens that can be used as a governmental guide.
Lettuce Harvest Video Links
The following list of videos and corresponding comments were provided by Mike Dentinger, VP at Trimble (Thanks, Mike!)
- 22:57 Extension video. Very good overall video of the Lettuce Ag cycle.
- Lettuce Production in the Salinas Valley
- 1:43 Short video, a bit older...but many practices are the same.
- 1:36 Church Brother Video (2019) - Nice job Josh! Shows the coring process for lettuce to be chopped.
- 5:42 - Pretty good video
- 4:18 Taylor farms growing Lettuce in Yuma
- 1:29 (2017) Harvesting Romaine hearts
- 4:53 USDA(2018) Organic overview...didn’t know they planted flowers in the lettuce beds…
Iceberg Lettuce Harvest Videos Folder: https://drive.google.com/drive/folders/1Kqo0qczNg5AxugxQNwTEcNtxlJq5HtOM?usp=sharing
Automatic or Robotic Lettuce Harvest Videos
- https://www.youtube.com/watch?v=EFC3OvkVKaQ (0:46) Cambridge, simple spotting system
- https://www.youtube.com/watch?v=xs4ypRAPc-c (2:35) Indoor Lettuce (Japan, “Lettuce Factory”)
- https://youtu.be/JagcPgRfGoo (2:32) Romaine, total cut of lettuce.(Ortomec 9700) (From Article on Church Bros. feat: Josh Ruiz) https://www.growingproduce.com/vegetables/automation-in-vegetable-harvesting-picks-up-the-momentum/
- https://www.youtube.com/watch?v=VjAXX-PCwjI (1:37) Another Ortomek video
- https://www.youtube.com/watch?v=dLCRxTQ73FA (2:23) Terrateck baby leaf harvester
- https://www.youtube.com/watch?v=KJHBaUs7vWc (7:05-finish) Cabbage harvester
- https://www.youtube.com/watch?v=NEo3jGkqIP0 (2:20) Automated Harvesting LLC - IM-500G1 Iceberg Automated Machine