• There are many factors to consider when planning and establishing a citrus grove, including; citrus variety, pest and disease history, soil fertility, soil moisture, water access and quality, and weather (freeze risk).
• Grove design is of particular importance, as determining orientation and spacing is vital to optimizing sunlight. Other considerations include; the vigor of the rootstock, the expected lifespan of the grove, possible row length, and direction of water drainage.
• Row spacing is the chief infrastructure priority. Rows must be wide enough for equipment to access without damaging trees or limbs, typically 18-22 feet, but should be kept as narrow as equipment allows to maximize trees per acre. For example, spacing 18’ between rows and 8’ within rows allows for 302 trees per acre (typical) whereas 22’ rows with 12’ within rows cuts the tree/acre count to 165. However, fewer trees per acre might be necessary due to climate, soil, scion variety, rootstock, or expected disease pressure.
• Mandarin/tangerine groves usually average 180 trees/acre with 12’-20’ spacing. Some citrus trees are self-pollinating, others require pollinizer trees to be planted within the grove.
• More densely planted groves have been shown to return more fruit earlier in the life of the grove, though the overall potential yield of each tree may be lower, and the grove may require more pruning throughout its life.
• According to one cost study in California in 2021, the establishment cost of an acre of orange grove is around $10,407, with the cost of orange trees (207/acre) and tree aids (ie. foam-type tree wraps) alone totaling $3,870/acre.
• Different types of citrus trees have meaningfully different characteristics. Grapefruit trees tends to grow to 20’ in height, whereas lemon trees might reach anywhere from 10’-20’ with sharp, thorny branches. Mature mandarin or tangerine trees reach up to 25’, and tend to have weaker limbs.

• Tree rootstock affects scion vigor, canopy architecture, yield, fruit size and quality, disease susceptibility, and pest tolerance.
• When selecting a rootstock; soil type, soil pH, pest and disease pressure, desired tree space, and other horticultural traits must be considered. Selection of scions add an additional layer of complexity, because scion varieties effect field performance, disease tolerance, and fruit quality. The rootstock/scion interaction is also a key factor to consider.
• Matching rootstock to unique soil types is critical, especially considering soil nutrients, drainage, and a rootstocks tolerance for high pH and salinity.
• Some rootstocks are also much more tolerant than others to diseases. HLB (Huanglongbing/Citrus Greening Disease) is currently the biggest concern to the citrus sector in the US, and though no rootstock has shown high levels of tolerance to HLB, some rootstock cultivars have been identified that produce good yields under high HLB pressure. Rootstock selection can be particular important for navel orange production in Florida.
• Rootstock has a significant bearing on the final size and productivity of the citrus tree, and therefore goals around tree spacing and size are important to consider when looking at rootstocks.

Source: University of Florida

• The citrus pruning process adjust tree shape, adjusts key ratios (between framework/fruit bearing canopy and top/root), and alters the food storage status for the tree. Pruning is generally required to avoid overcrowding or excessively tall trees, and therefore more pruning is required the more densely planted the grove.
• Pruning activities in groves mainly consist of heading back and thinning out. Heading back removes the terminal portion of a shoot, stimulating lateral bud breaks to create a more compact tree. This can be done with mechanical hedging and topping. Thinning out involves the removal of complete branches and generally must be done with hand-held equipment, and therefore is less frequently carried out as it is considered too labor intensive.
• Most trees do not need pruning in the first few years, especially if protective wraps (which reduce sprouting) are utilized.
• Mature trees need relatively limited pruning until they reach containment size, or the total planned sized of the mature canopy, at which point the tree will be hedged to contain trees and alleviate crowding.
• Hedging is usually done at an angle so that sunlight can reach even the lowest levels (or ‘skirts’) of the tree. A 10 to 15 degree angle is generally considered satisfactory, though wider angles may lead to better spray coverage and more efficient harvesting (since more fruit is accessible to ground-level pickers).
• Topping is also critical to ensure that trees do not become overly tall, and must be managed carefully. Topping trees increases light penetration, reduces harvesting costs, enhances spray coverage, and can increase fruit quality and size. Common topping heights are 15’-16’ at the peak.
• Adopting a regular pruning program protects trees, yields, and reduces costs. Tree health is maintained due to the avoidance of heavy cutting and elimination of large cuts, in addition to the avoidance of excessive vegetative growth that can limit fruit production. Reducing the amount of material removed also reduces costs related to removal of limbs and brush from the grove. Common pruning programs are 2-, 3-, or 4-year programs, where one side of a row is trimmed some years, the other the next, and the top in the next.
• Hedging is generally done sometime between the end of harvest and the next bloom, though it is important to avoid hedging or topping when freezing temperatures are still a danger.
• Skirt pruning is sometimes necessary to allow equipment (like herbicide booms) to move more freely through a row (or middle). Skirt pruning can also help avoid damage to low lying limbs and decrease the incidence of footrot, which is caused by poor air circulation under the tree canopy.
• Pruning is also a strategy to be utilized after freeze damage has occurred, or to induce new vigor in older groves.
• Root health management is a related consideration.

• Tree water usage depends on the tree’s age, size, species, climate, and soil type. Research has found that mature citrus trees consume about 60” of water per year.
• Growers in different areas in the US tend to utilize different standard irrigation systems. Growers in more water abundant landscapes often utilize basin or flood irrigation, whereas drip or microsprinkler emitters are more common in water constrained environments like those in Arizona or California.

• Salt build-up in citrus irrigation waters can cause root dieback and leaf loss, which is more of a problem the more poorly drained the soils.
• “Recent research has further indicated that distributing irrigation across the week with more frequency and less volume increases water use efficiency and improves water uptake by HLB-affected trees, thus improving yield. For example, if 3 hours/week of water are required, irrigation should be distributed in daily 30-minute applications for five days.” —University of Florida Extension
• Modern irrigation management generally involves water budgeting, soil water measurement (especially through the use of probes), and smartphone apps.

• Fertilizer and soil amendments are applied in most groves annually, often through a drip line or through foliar application. Fertilization rates vary depending on a variety of factors, including soil type.
• Leaf and tissue samples are regularly taken for nutritional analysis during the fall.
• Some varieties of citrus, like mature Navel orange trees, may require a growth regulator treatment like Gibberellic acid, which can help minimize pre-harvest fruit drop.
• Weeds on the grove floor are managed through spot sprays of herbicides, as well as discing the middles during the spring.
• Insects in the grove are managed through foliar treatments, often multiple times per season. These are applied in late spring to early summer with a UTV and a small, pull-type sprayer, especially early in the groves’ lifecycle. Spot treatments will likely be required after that.
• Disease in the orchard is managed with Kocide (copper) and hydrated lime applications. Growers often higher applicators to apply insect/disease materials with a ground-based air blast sprayer.
• If the area has been planted to citrus in the past, it may be necessary to test for Nematodes and Phytophthora, which can be managed through resistant rootstocks, irrigation management, and chemical applications.

• Due to the alternate-bearing nature of many citrus varieties (a year with heavy yields are followed by a year with a very light yield), it is important to manage pruning appropriately, especially with an eye to controlling fruit size during alternate bearing years. For example, hedging or topping after a light crop can reduce the number of fruit with a corresponding increase in fruit size and reduce the effects of alternate bearing.
• Fruit size can be specifically managed through a number of different practices, including;
• Flower suppression
• Pruning
• Chemical thinning
• Hand thinning
• Harvest timing
• Manipulating nutrition and irrigation

Most citrus varieties are hand-harvested and field packed, and each field is usually picked 2-3 times, due to the fact that citrus fruits often ripen non-uniformly, meaning harvest on one farm with multiple varieties can last several months. Harvest is often carried out by a custom harvester— which is usually a farm labor contractor who hires workers directly and moves from farm to farm to harvest.

• 1/3 of the orchard is picked in each of three harvests over the growing season (Navels, for example, are picked from November to June).
• Oranges that are destined for fresh markets, for example, are picked by workers on ladder, placed in a bag, and when the bag is filled, the worker transfers the fruit to a field bin. Oranges that are destined for juicing markets are more likely to be harvested mechanically, though this practice has become less common in Florida because it can lead to damage amongst trees made vulnerable by citrus greening diseases.
• A field bin holds 900 pounds (24 cartons) of oranges. One acre of orange grove at its peak yield might produce as many as 30 field bins, or 550 packed cartons/boxes (35-40 lbs each). When citrus is destined for processing/juicing, it is usually placed in a tub instead.
• Once the field bins are full, they are collected and transported to a central location in the grove to be loaded into bulk trailers. This process is called Roadsiding.
• Fruit is hauled to a packinghouse to be washed, graded, sized, and packed, and all costs related to picking, packing, hauling, and marketing are generally paid by the grower. Prices for these services vary considerably depending on the region, but one estimate put costs, all inclusive, at around $6.20 per carton.
• Harvest and hauling practices and prices can vary depending on what kind of citrus is being harvested and in what region. Specialty varieties that need special handling due to stem-on or thin skin, or that need to be shipped in partially loaded trailers to prevent damage to fruit at the bottom of the load, are likely to cost growers more. Some regions, like Florida’s tarping requirement, also have additional requirements around harvest and transport to prevent the spread of disease.
• Harvest timings and practices are dependent on the variety of citrus. Lemons, for example, are generally harvested when juice content reaches 25%. Due to the risk of oil spotting (bruising of lemon peels), hand harvest is generally necessary for fruit and cannot be carried out when fruit is wet. The maturity of mandarines/tangerines on the other hand is often measured using brix/sugar level, fruit firmness, or shine/gloss of the peel.

• Frost protection. Though this is not a concern in many areas where citrus is grown, in parts of California, Texas, and northern Florida, it can be. To combat the impacts of frost on citrus trees, growers control grove ground cover, apply water, and utilize wind machines to raise the temperature in the grove and head off the worst impacts of frost.
• Depending on the region, citrus growers may have to pay assessment fees. In California for example, growers much pay a fee of $0.08 per carton to support disease prevention, as well as $0.03/carton to the Citrus Research Board. Som growers also pay a small fee $10.56 per acre on average) to the Central California Tristeza Eradication Agency— though this assessment is optional.
• The overall size and scale of the farming operation, and what other crops/varieties the farmer grows.
• Whether the land is owned or managed by the grower.
• Infrastructure availability (road access, irrigation systems, building locations, etc.

The combined effect of Citrus greening (commonly known as Huanglongbing or HLB) and citrus canker have wrecked havoc on the US citrus industry, especially in Florida, since the mid-2000s.

Source: Citrusgreening.org

The abnormally hard fruits that develop on trees infected by citrus greening taste bitter, have an unusual green color, and are therefore not fit for consumption or processing. The disease is incurable and lethal to infected citrus trees, usually within a few years, and has wiped out millions of acres of groves around the world. HLB has been detected in all citrus-growing regions of the US, but has not become an issue in commercial orchards in California.

More than 90% of Florida’s citrus trees have been effected by HLB, reducing production for the juice market by 72%, and causing more than 5,000 (of around 7,000) citrus growers to exit the industry alongside 2/3rds of all citrus processors in the state.

There are strategies to control the spread of the disease, including replanting healthy saplings, removing diseased trees, controlling pests, and carefully managing soil nutrients, this dramatically increases the cost of production (by some estimates by as much as 3x), often making it impossible for growers to remain economically viable, especially in juicing markets.

Scientists are making progress towards a solution that might provide an antibacterial antidote to trees infected with citrus greening, though commercialization is likely still years away. Gene editing and breeding for resistance offer other possible solutions in the future.

Another possible solution is adaptation, especially through the adoption of advanced production systems (APS), which compensate for the smaller and lower yielding characteristics of effected trees by increasing the density of orchards. This strategy has been show to result in higher efficiencies related to advanced fertigation, greater canopy growth, and fruit yields for less water and fertilizer inputs compared to conventional production systems.

Source: Citrus Industry, UFL

Citrus canker is another contagious bacterial disease that has effected lime and grapefruit trees in particular, and an outbreak began in Florida in 1995.

These two diseases have led to the abandonment of at least 64,000 acres of orange groves in Florida.

In the past, demand for oranges and orange juice were the key driver of the citrus market, followed by demand for grapefruit. However, in recent years, consumers have preferred fruits that are easier to peel, are segmented, and seedless, which has led to a rise in tangerine demand and production even while demand for and production of oranges and grapefruits continue to decline, respectively by 71% and 80%.

However, the most relevant shift in consumer preferences and related demand in recent years has been the fall in demand for orange juice. Despite the fact that US consumers tend to consume more juice than fresh fruits, health concerns, especially related to sugar content, has caused demand to fall. Though that trend holds true for oranges and grapefruit, but lemons and other citrus have seen a positive trend in fresh fruit and juice consumption.

Source: Choices Magazine, Trends and Challenges Facing the US Citrus Industry

Freezing temperatures, especially persistent freezing temperatures, can cause severe damage to citrus groves, drastically reducing yield and damaging trees such that production can be effected in subsequent years.

Winter freezes have caused significant deleterious effects to groves both in California and Florida, with as many as four freeze events in the last decade.

Lemon trees in particular are exceptionally sensitive to frost, which is a key reason why much US lemon production takes place in Arizona and California, and much less in Florida, due to the risks of yield loses due to freeze events.

Labor shortages and high wages pose a threat to the US citrus industry, as labor often makes up 40%+ of a citrus groves operating expenses.

The costs of utilizing the H-2A program, or alternatively, the risks of hiring undocumented workers, have increased in recent years in all citrus markets.

There is growing pressure in Florida in particular. Though mechanical harvesting was common in the past in groves where fruit was bound for the juice market, mechanical harvests tend to do more damage to trees already impacted by citrus greening/citrus canker, and so there has been a general return to hand harvesting.

A 2020 Citrus Industry magazine story titled, “Harvesting Labor a Concern” included the following excerpt:

Peace River Valley Citrus Growers Association Executive Director Kait Shaw said some citrus harvesters could leave later this season. “We will see a potential problem when the other commodity crops are ready to be picked and those workers who were originally contracted will not be able to cross the borders, therefore leading to a bidding war over the laborers who are already in the state of Florida,” she said. “As of right now, the majority of our members are good with their availability.”

Though markets around the world have also been impacted by citrus greening and citrus canker, US producers have found it particularly expensive to manage the costs associated with responding to the issue.

Source: US Citrus Production: An Uphill Battle to Survive

As global competitors like Brazil, India, and China have seized greater and greater shares of the global market for citrus, the US’s ability to find scale and compete on price has becoming increasingly inhibited.