How mastic gum is harvested

As you open a tin of mastic gum and see the resin nuggets or droplets, you may wonder - how did they get from a tree in Greece to the tin in your pocket?

Beginning every summer in July, mastic gum is harvested by hand on the Greek island of Chios using traditional, centuries-old techniques. Farmers carefully cut into the bark of mastic trees and then, a couple of weeks later, collect the resin, or “tears,” the trees release from these incisions.

While the main part of the harvest takes place in July and August, mastic cultivation requires work throughout the entire year. From preparing the land to cleaning and processing the resin, we describe the steps that take mastic from the orchards of Chios to your Greco Gum tin.

On a visit to Chios in May 2024, the Greco Gum team had the chance to meet with mastic growers, tour their farms, and learn first-hand about this ancient and labor-intensive tradition. Combining what we learned in the field with resources from the Chios Mastiha Growers Association and additional research, this article explains how mastic gum is harvested.

Preparation

Timeline: winter and spring

Although harvesting resin from the mastic trees doesn’t start until July, Chios mastiha farmers work throughout the year to produce a high-quality product. During the winter and spring, growers prune the trees and clear the land to make it easier to harvest the natural resin.

Fertilizing the soil

Timeline: December–February

Farmers fertilize the soils in the mastic orchards in December, January, or February to ensure the trees have the nutrients they need to grow, remain healthy, and produce resin.¹

Pruning the mastic trees

Timeline: January–February

The shrub-like mastic trees that grow on Chios (Pistacia lentiscus var. Chia) are pruned annually to create better growing conditions and facilitate the harvest of mastic tears.

Mastic growers prune the trees each winter, usually from the beginning of January to mid-February.² Pruning methods are typically based on experience, with growers using techniques passed down from generation to generation.

During the pruning process, growers remove any dead and dry branches to help the tree grow stronger. New growth at the base and middle of the tree is also removed, leaving a leafy canopy on top of a strong trunk. This ensures enough sunlight and air gets through to each tree, while also making it easier for farmers to collect resin during the mastic harvest.¹²

Clearing the land & preparing “the plate”

Timeline: June

Harvesting mastic requires a flat surface beneath each tree where the mastic can fall and then be collected. To make this possible, growers must clear all undergrowth and debris that would make it harder to collect the resin from the ground.

Starting in June, farmers weed the land in the mastic orchards and clear out any branches that have fallen. Next, they sweep away leaves and other debris and flatten the soil to create a clean, level surface called “the plate.”¹²

This is a crucial step in the mastic harvest: starting with a clean area beneath each tree makes it easier to collect, sift, and clean the resin that falls to the ground.

Once the area is clear and the soil compacted, growers spread a chalky limestone powder (calcium carbonate) beneath the trees. The white soil, known locally as asprohoma, keeps the mastic cleaner and helps prevent it from sticking to the dirt. It also helps keep away bugs and pests that could harm the mastic trees.

Cutting the bark of mastic trees

Timeline: July–August

The next step in the mastic harvest is cutting the tree bark. Starting the second week of July, farmers begin making careful incisions in the bark in a process known as kendima, kentima or kentos (translated as “embroidering” in English).¹ The tree releases resin as it heals from these cuts, which then begins to harden as it dries.

According to the Chios Mastiha Growers Association, the kentima usually lasts around 75 days, but the duration varies depending on weather conditions. Mastic farmers work in sections, starting with the bottom of the tree and working their way up. They then move back to the base of the tree to make fresh incisions over the course of the harvest season from July to August, and occasionally into September.

Growers determine how many incisions to make in each tree, drawing from their experience and knowledge passed down to them through generations. The number of cuts they make is determined by factors like the tree’s age, size, and overall health. It can range anywhere from 20 to 600 incisions per tree.²³

Each incision is about 1.5-2 inches (4-5 centimeters) deep and 4-6 inches (10-15 centimeters) long.⁴

Harvesting and collecting the resin

Timeline: August–September

Chios mastic resin is collected in several rounds from mid-August to the end of September. This phase of the harvest is one of the most challenging and labor-intensive, as the resin has a very sticky, sap-like texture when it’s fresh.

After cutting the tree, farmers wait for the resin to drip onto the plate and leave it to dry in the field for around 15 to 20 days.² This drying period allows the resin to start its months-long hardening and crystallizing process, making it less sticky and less challenging to collect.

Next, harvesters go through the orchards and begin to collect the mastic pieces. Since mastic is a valuable product, leaving it in the orchards for too long exposes farmers to a lot of risk from potential rains (mastic can be ruined if it gets wet before it has had time to fully dry and cure) and other damage.⁵

Larger pieces of mastic (also called “pita”) are the most valuable and are collected more often. These pieces can be collected by hand and generally do not require too much sifting in the field.

Smaller pieces require additional sifting and are collected less often, usually towards the end of the harvest season. The process has several key steps:

1. Scraping: Starting in mid-September, farmers scrape the mastic droplets off the trees using a tool resembling a tiny rake.
2. Collecting: Using a brush and dustpan, harvesters sweep the smaller pieces of mastic together with the white soil into a pile and then put this mixture into a sifter.
3. Sifting: Next, harvesters sift the resin droplets in the field. This process removes dirt and some debris, but many leaves and small pieces of bark are left behind, mixed in with the mastic resin. These are cleaned later on (see below for more details).

Drying and curing mastic

Timeline: September/October to November/December

Once the mastic has been collected, it needs to dry for up to a few months before the next round of cleaning can begin. As mastic dries, it solidifies, becoming less resinous and sticky. After it has crystallized, it’s easier to sort and clean.⁶

Small pieces are placed into burlap bags, together with the remaining leaves and bark that was collected in the field, while larger pieces of mastic are placed in wooden trays. The mastic is left to dry for several months in a cool, underground room resembling a cellar, typically located in the producer’s home.

Cleaning, sorting, and processing mastic

Timeline: November–early spring

Cleaning mastic is also a very labor-intensive part of the harvest and production process. First, the mastic undergoes multiple stages of cleaning, sorting, and classifying in the mastic villages, followed by additional cleaning, sorting, grading, and processing at a larger facility run by the Chios Mastiha Growers Association.

According to the Growers Association,”the entire production and cleaning process of Chios Mastiha is free of all chemicals and additives and has remained unchanged throughout the centuries.”

Cleaning & sorting

In November, women in the mastic villages begin cleaning the dried resin by hand. The smaller pieces dry faster and are typically cleaned first as the larger mastic pieces continue to dry. This process requires attention to detail and experience and impacts the price producers are able to get for their product, with cleaner resin commanding a higher price.³

The cleaning process has several stages:

1. First, the women separate the mastic from the remaining leaves, bark, and other debris. As they remove the debris, some producers also loosely sort the mastic according to size using different-sized sieves.⁶
2. Next, the women do a more thorough cleaning using a small knife to cut dirt out of each individual piece of mastic, a process known as pinching. Sometimes the mastic is also washed by hand in natural spring water.
3. Once the mastic is sufficiently cleaned by hand, it’s taken to larger facilities run by the Growers Association for more thorough washing and cleaning with the help of machinery, as well as grading and quality inspection for impurities.

Grading

Producers make an initial classification of the mastic based on its size and quality. Each mastic village has one large sorting machine from the Growers Association, so farmers can separate mastic pieces according to size before it is sent to the Association for the final round of cleaning.

The Chios Gum Mastic Growers Association takes over the remaining processing, sorting, and grading based on size and color.² Grades range from 1 to 5, with Grade 1 being the purest form of mastic safe for food use.⁷ Lower grades of 3-5 are suitable for other uses, such as cosmetics, perfume, essential oils, and varnish.

Processing

Once the product reaches the Chios Mastiha Growers Association, it’s packaged for sale as raw mastiha or further processed into chewing gum, mastic oil, and other products.²³

Conclusion

Mastic gum is produced and harvested only on the Greek island of Chios, located in the northern Aegean Sea. Growers in the mastic villages use traditional cultivation methods passed down through generations, with mastic resin harvested and cleaned by hand.

The main harvest takes place between July and September when the mastic trees are cut and the resin is collected after it falls to the ground.

However, mastic cultivation and gum production requires year-round labor. From preparing a flat, clear surface beneath each tree before the harvest season to drying and cleaning the mastic through the winter, care is taken at every step of the process to ensure the end result is a high-quality product.

This article originally appeared online in 2024; it was most recently updated on September 27, 2024, to include current information.

Jon Persson

Jon is one of three co-founders of Greco Gum. He lives part-time in Chios, Greece and enjoys learning about the island’s rich cultural history and sharing it with the rest of the world.

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