How Do Olives Grow?

 

USDA Hardiness Zones 9 - 11

 

Olive trees are shallow-rooted evergreens with lifespans that extend many hundreds of years. 

 

Olive trees are alternate-bearing.  The fruit is borne on wood that grew on the tree the previous year.  For instance, if the tree bears a heavy load of fruit one year, it lacks the resources to produce much wood (shoot growth) that year, and therefore will produce a light load of fruit in the following year. In lieu of fruit, the tree will produce excess shoot growth during the year of light olive growth and will once again bear a heavy load of fruit the following year. This alternating pattern may be managed through diligent pruning and by taking care to supply the tree with adequate resources when it is supporting a large olive crop.

 

Seasonal Growth

Health Benefits

 

Olives have been lauded for their health benefits since the days of ancient civilizations.  Today, cardiologists suggest that two tablespoons of extra virgin olive oil a day helps to keep the doctor away. Here’s a look at what one of the world’s oldest cultivated fruits has to offer:

 

Olives contain dozens of health-protective phytonutrients, and the many preparation methods to make the bitter fruit palatable actually enhance its anti-inflammatory and antioxidant nutrient levels. 

 

Hydroxytyrosol is a phytonutrient primarily found in olives that recent medical science has hailed as the “superstar of antioxidants” due to its ORAC (Oxygen Radical Absorbance Capacity) value of 68,576--the highest level ever recorded in a natural antioxidants. Its ability to absorb cell-damaging free radicals is 15 times greater than the antioxidants found in green tea. 

 

Hydroxytyrosol is the only phenol able to cross the blood-brain barrier, allowing it to absorb free radicals in the Central Nervous System. It is both fat and water soluble, giving it the highest bioavailability of any antioxidant, and is rapidly absorbed into blood and tissues. Its free radical-scavenging prowess protects cells and mitochondria from damage. 

 

Recent studies have also indicated that hydroxytyrosol is valuable in the prevention of bone mass loss. Increased calcium deposits in the bones and decreased bone loss are present in studies linked to the mass consumption of the phytonutrient. 

 

Olives play a role in an anti-allergenic diet because they are shown to work as anti-histamines at the cellular level. The anti-inflammatory benefits of olives may be linked to the olive’s role in blocking histamine (H1) receptors, lessening the cell’s histamine response.

 

Oleuropein, a bitter phytonutrient found exclusively in olives, decreases LDL cholesterol oxidation, lowers levels of oxidative stress, and protects nerve cells from damage related to oxidation, offering natural protection against a variety of forms of cancer. 

 

Oleocanthal, a phytonutrient in olives, mimics the anti-inflammatory effects of ibuprofen, naturally decreasing the risk of breast cancer. 

 

Approximately 80 to 85% of the calories in olives come from oleic acid, a monosaturated fatty acid, which is associated with reduced risk of cardiovascular disease. When diets low in monosaturated fatty acid are altered to include a healthy amount of monosaturated fat content, the result includes lowered blood pressure and lowered LDL (bad) cholesterol levels.

 

A diet rich in olive oil, low in saturated fats, moderately high in carbohydrates, and soluble fiber from vegetables, fruits and grains helps to improve blood pressure control and enhances insulin sensitivity in diabetics. 

 

The monosaturated fat levels in olive oil are linked to healthy arterial function in elderly individuals. Daily consumption of olive oil has also been linked to the prevention of stroke, dementia and even depression via studies that focus on reduction of vascular risks. 

History

 

Fossilized olaea pollen has been found in Mediterranean regions such as Macedonia, Greece, indicating that the genus is native to the Mediterranean. It is also possible that the genus originated in northern Africa and arrived in the Mediterranean basin via trade with Egyptians. 

 

Throughout civilizations across the world, the olive branch has been used as a symbol of peace, abundance, wisdom, purity, power and glory for thousands of years.

 

The olive tree is among the oldest cultivated trees in the world, with a history that pre-dates the written language. Ancient evidence of olive tree cultivation has been discovered in Crete, Palestine and Syria, dating back 6,000 years. The first documented commercial cultivation of olive trees dates back to 3000 BCE, in Crete, where the crops are thought to have been the source of the Minoan civilization’s wealth. In Egypt, olive branches dating back to 1,300 BCE were discovered in the tomb of  the pharaoh, Tutankhamun - King Tut.

 

Olive oil was used to anoint the heads of kings in ancient Greece and was burned in sacred lamps in temples during religious ceremonies. Ancient Greeks also applied olive oil to their hair and skin for good health. In the original Olympic Games, olive oil burned the “eternal flame” and winning athletes were crowned with olive tree branches. References to olive trees are abundant across the canon of Greek mythology, and ancient Athenian coinage bears the image of the olive branch. The ancient Romans also held the olive in high dietary regard.

 

Olives were also important in ancient Israeli and Hebrew cuisine and culture, and appears multiple times in the New Testament. In Islamic culture, too, the olive tree is mentioned several times in the Quran as a sacred tree and precious fruit. Olives are consumed in place of dates (when not available) during Ramadan fasting.

 

The olive tree arrived in the Americas by way of Spanish colonists who brought seeds to present-day Peru and Chile.  South America’s dry Pacific coast is very similar to the growing conditions in the Mediterranean and the new crop did well there. In the 18th century, the Spanish planted the first olive trees in present-day California. By the 1860s, olive tree cultivation had became a very successful commercial crop there. Most olive trees grown in the United States are still typically grown in California to. 

 

As of the 21st century, there are an estimated 865+ million olive trees in the world. In 2011, there were 9.6 million hectacres planted with olive trees, making them the most extensively cultivated crop in the world after coconut and palm trees. 

Propagation

 

The two most common ways to propagate olive trees are by seeds and by cutting. Both methods will yield a transplantable tree within one year, however, olive trees that are propagated by cutting mature more quickly and bear a closer resemblance to the parent tree, in terms of fruit production and growth habit.

 

Harvesting

 

Olives are harvested at different stages of ripeness - green-ripe, turning color, and naturally black-ripe. Green-ripe olives, which release a creamy white juice when squeezed, are harvested when they are an even colored shade of yellow-green. If they are allowed to ripen further on the tree, green-ripe olives begin to turn to a reddish-brown color, though they are still firm, when they are in their turning color phase. At the naturally black-ripe phase, olives are fully ripened on the tree in a dark purple or black shade, and release a reddish-black liquid when squeezed. Olives reach the naturally black-ripe phase approximately 3 to 4 months after the green-ripe stage. 

 

Traditional methods of harvesting olives include combing the ripe fruit from the tree and into nets, or by hand-picking the fruits. In commercial crops, mechanical pickers are utilized to harvest large quantities of olives.

 

Storage

Green-ripe olives store better than naturally black ripe olives, which need to be processed within a few days after picking. For best quality, olives are stored in well-ventilated crates at 41 to 50 degrees Fahrenheit. Extended exposure to lower temperatures may cause injury to the olives,  such as internal or skin browning. 

 

Olives are cured by a variety of methods to remove their bitterness. The most common curing processes use water, brine, dry salt or lye treatments to leach the bitter-tasting, water-soluble compound, oleuropein, from the olive flesh.

 

To water-cure olives, olives are individually cracked or cut so the oleuropein leaches out more easily, and olives are soaked in water that is changed daily over at least a week (depending on desired bitterness). After the olives are cured, they are placed in finishing brine (a vinegar and salt solution) to flavor. Water-cured olives have a more bitter flavor than olives cured with brine, dry salt or lye, because water-curing removes less oleuropein than other methods.
 

Fun Facts

 

The ten largest olive-producing countries, according to Food and Agriculture Organization, are all located in the Mediterranean, and account for 95% of the world’s olives.

 

Spain, Italy, Greece, Turkey, and Morocco are the top five producers of olives (FOASTAT, 2011).

 

Products - How are olives used?

 

90% of all olives harvested are used to make olive oil, while approximately 10% are used to make table olives (green-ripe, turned, and black or ripe olives that have been cured and fermented). The culinary uses for olive oil and table olives are myriad.

 

The olive tree itself is also used for its fine wood and olive leaf.

 

How is olive oil made?

 

Olive oil is made from pressing whole olives to obtain their fat. 

 

Traditionally, olives were shaken or beaten from trees, but they are a soft fruit that is easily bruised and needs to be treated delicately. Once bruising occurs, the olive’s benefcial oils immediately begin to degrade, and any damage to the fruit can trigger oxidation and fermentation, which degrades the flavor of the olive oil. Today, most premium olive oil producers ensure that their olives are hand-picked to produce the best quality olive oils.

 

Once olives have been picked, separated from any remaining stems and leaves, and washed, they are ready to undergo the process of pressing. Traditionally, olive oil was processed using large stone wheels to press olives, but most modern processors are stainless steel rollers. Pressing grinds olives into a paste. Water is then added to the paste through a process called malaxation, which allows the oil molecules to clump together.

Following malaxation, the mixture is stirred for 20 to 40 minutes. The longer the mixture is stirred, the more time the oil has to absorb flavors from the olive paste. However, longer mixing times allow more oxidation to occur, producing free radicals that degrade the oil quality. Cold-pressed olive oil comes from a modern mixing process that utilizes closed mixing chambers filled with a harmless gas that prevents oxidation, improving the overall quality and yield.

 

After being mixed, the paste is sent through a centrifuge that extracts the oil, separating it from the remaining paste. This solid, remaining paste is called the pomace. Some manufacturers use steam, hexane or solvents to extract the remaining, low-quality oil, which is labeled as pomace oil. 

 

Refined vs. Unrefined Olive Oil:

 

Refined olive oil: Refining olive oil is a process that uses solvents and high heat to neutralize the taste of olive oil. This process is used with low-quality olives and olives that have been damaged or oxidized through the mass production process. Due to its chemical neutralization of poor flavor, refined olive oil may be blended from a variety of sources. It is labeled as “pure olive oil” or simply “olive oil” in stores. Approximately 30% of the olive oil on the modern market is refined.

 

Virgin and Extra-virgin olive oil:  Unrefined olive oil or “virgin” or “extra virgin” olive oil does not undergo chemical refinement. Unrefined olive oil is made from olives that are in good condition and have not had their taste altered by oxidation or other contamination. “Extra virgin” olive oils are the highest quality, maintaining the true flavor of the olive, as well as the highest nutrient content.

 

Grow it Yourself

 

Olive trees are hearty and capable of growing in areas with poor soil or scarce water. However, they are intolerant of hard freeze conditions. If the temperature drops below 22 degrees Fahrenheit, olive trees may sustain damage to their smaller branches, and temperatures that drop below 15 degrees Fahrenheit may be fatal. However, olive trees do require some cold (below 45 degrees Fahrenheit) for proper flower development, so many varieties will not produce fruit in tropical environments for this reason.

 

To propagate olive trees from seed, plant approximately one month before the last frost in spring. Because olive tree seeds have a low viability rate, multiple seeds need to be planted to ensure germination of at least one seedling.  

 

1. Use a pair of pliers or nail clippers to crack the seeds, allowing the endocarp (pit) to crack, without cutting all the way through the seed, and place cracked seeds in a bowl of water. Allow them to sit overnight to prompt germination and hydrate the embryo.

2. Prior to planting, drain the seeds on a sheet of paper towel.

3. Sow the seeds ¼ inch deep in four-inch pots filled with a mixture of 50% washed sand and 50% seed compost. Seeds should be kept under cool conditions during their early life. For the first four weeks, keep the pots in a sunny, unheated room that maintains a temperature around 55 degrees, graduating to a propagation mat that is set to 68 degrees after the first month. Add moisture to the pots when the soil feels dry beneath the surface. 

4. Once daytime temperatures rise above 65 degrees (after the last frost of spring), place the pots outdoors under light shade. Olive tree seed germination occurs in one or two months, but some varieties may take slightly longer. 

5. Once the seedlings grow to three inches in height, transfer them to nursery containers filled with 50% loam and 50% washed sand, acclimating them to full sun exposure over the course of one week. 

6. Olive trees may be planted (15 feet apart) in the spring or autumn of their second year, when they possess a sturdy lead stem and several mature leaves. 

 

To propagate olive trees by cutting, wait until summer, when the current season’s growth has begun to harden and the blossoms have faded. 

 

1. Fill an eight-inch container with a half-and-half mix of washed sand and peat. Saturate with water and press to expel excess, then poke a hole four inches deep in the mixture. Gather an eight-inch, semi-hardwood cutting from the tip of a healthy olive branch, and remove all leaves from the base. Leave approximately six leaves at the tip of the cutting. Coat the severed end of the branch with 0.2% IBA rooting talc, and insert the cutting into the hole in the soil mixture, firming the soil around it.

2. Place the pot on a propagation mat set to 70 degrees in a lightly shaded, well-ventilated area, and mist the foliage twice daily with a spray bottle of water. If sand feels dry in the top inch of the pot, add more moisture. Roots will emerge in approximately three months. To check for roots, tug the cutting gently from its base. After the tree has rooted, the propagation mat may be turned off. Continue to grow in a cold frame with weekly watering during winter. Keep indoors in temperatures that drop below 25 degrees Fahrenheit.

3. After the last frost of spring, the olive tree can be moved to a lightly shaded part of an outdoor garden. Provide one inch of water per week during the summer, and transplant to a permanent bed in autumn.