Citrus 101


Growing and Packing

From rootstock to your produce market, Sunkist® citrus fruits are coddled and pampered each step of the way to provide you with the quality and great taste you've grown to love.


Plant a citrus seed from a Valencia orange and what do you get? A Valencia orange tree just like the one your seed came from? Nope! You can never be sure exactly what you'll get because, with a few exceptions, plants grown from seed are all slightly different.

Naturally, citrus growers want to make sure all their trees produce the same high quality fruit. To do this, each new tree they plant is grown, or propagated, by grafting or budding instead of by seed.

Look closely at most citrus tree trunks and you'll notice that the scion, or top of the tree, is a different variety from the roots or rootstock of the tree. Citrus growers plant trees that are put together from two different sources. The rootstock comes from a tree that is known for special qualities like disease resistance, while the scion comes from a tree know for its quality of fruit, like a 'Washington' Navel orange or a 'Eureka' lemon. After the rootstock is a year old, a single bud is taken from a branch of the desired scion variety and inserted into the bark of the young seedling. This bud grows into the top of the tree that produces the fruit. Click here to learn more about how rootstocks are grown.

Info about how rootstocks are grown.

Back to top

Fruit Development

Citrus flower buds begin to form in early winter and develop through late winter and spring. More than 99% of citrus flowers fall off the tree. The ones that remain become fruit. Temperature and moisture are critical factors during and immediately after flowering.

Most pollination is done by insects, but some citrus can develop without pollination through a natural process called parthenocarpy. Some varieties, such as the "Clementine" Mandarin, require cross-pollination with another citrus variety.

Parthenocarpy is the main reason. If parthenocarpic flowers are not pollinated, they generally don't produce seeds. Some, like the 'Washington" navel, don't produce viable pollen.

After bloom, fruit development takes from five to 18 months, depending on the variety and growing area. Unlike many other types of fruit, most citrus can be left on the tree without becoming overripe.

Back to top

Soil Type

Citrus will grow in most soils from sandy to adobe clay, provided it drains well. Sandy soils must be watered and fertilized more frequently than soils with a higher clay content and growers can add organic matter such as manure or compost to improve water and nutrient holding abilities.

Back to top

Irrigating & Fertilizing

Water quality is very important. Water high in salt content, common in some desert regions, can cause injury to leaves, burning leaf tips and margins. Lower levels of salts can cause the tree to grow poorly or to produce fewer or smaller fruit.

Nutrients that citrus trees need in relatively large amounts are nitrogen, phosphorous, potassium, sulfur and calcium. In lesser amounts, citrus requires iron, magnesium, copper, zinc, manganese, molybdenum, boron and chlorine. Usually only nitrogen needs to be added, most often in late winter to meet the demands of spring bloom.

Back to top


Unlike most other fruit trees, citrus trees don't require regular pruning. Commercial growers trim tree tops to keep them smaller so they are easier, safer and less expensive to pick, and "hedge" the sides to let more sunlight into the trees to improve yields. Hand pruning opens up the trees to allow more sunlight into the center.

Back to top

Frost Control

Most citrus will freeze when fruit temperature drops to 27-28°F, so protection from frost is critical. The main methods of frost protection in California and Arizona are two low-tech devices -- wind and water. Large fans on poles lifted about fifty feet above the grove are turned on when the temperatures near freezing. The fans mix the slightly warmer air above the grove with the colder air near the ground, which warms the air around the tree.

By applying water to trees, the heat built up in the soil during the day is lost more slowly, and air temperatures around the fruit stay warm a little longer. A few growers still use oil-burning orchard heaters, but this once-common method is seldom used now because of the cost.

Back to top

Packing Citrus

Getting fruit from the tree to the table is complicated.

Fruit are carefully picked by hand and put into bins that hold about 900 pounds. The bins are hauled by truck to a packinghouse, where the fruit is pre-graded to eliminate the obvious culls (bad fruit) and washed to clean away field dirt and dust. The fruit's natural wax, removed during the washing phase, is replaced by a food grade, non-animal source wax to restrict moisture loss and extend shelf life.

The fruit is then graded, most often by electronic camera systems. After grading, the fruit is divided by size. The first grade fruit is stamped or labeled "Sunkist." An unmarked second, or choice, grade is also packed. Second grade fruit is just as sweet and juicy inside -- it's only the outside that has been a bit scarred by Mother Nature. The remaining fruit is sent to the juice plant.

Most oranges and grapefruit are packed with robotic carton packing machines in 40-pound cartons. Lemons and most tangerine cartons are volume-filled with a set number of fruit. The cartons are stacked on pallets and placed in a pre-cooler before being loaded on trucks or rail cars for transportation to markets.

Back to top