2.2.2 Harvesting Leaves and Stems

The aromatic herbs such as basil, bay leaves, mints, oregano, par sley, rosemary , sage, tarragon and thyme are often used fresh to garnish food, as dry seasonings or for extracted essential oils. The aroma, a function of their essential oil composition, is dependent on chemotype and specific chemotypes can be chosen for an end-use. The essential oil composition and yield will also change during the seasons, and crop harvest should be directed to maximise both the essential oil content and quality [17] . parameters. As a general rule, the leaf and stem should be cut when the growth has matured to a n elongated flower stem but without full flower or significant senescence of the lower leaves. The essential oil can be distilled from fresh or dry plant material. Harvesting the plant material should be avoided when it is wet and if it is to be dried the plant material should be evenly spread onto the drying racks or drier to ensure there is no sweating, fermentation and microbial invasion.

2.2.3 Harvesting Flowers and Buds

When flowers and buds are the source of a spice or essential oil, the harvest time can be throughout the year in the tropics or during a limited flowering season in temperate regions. As an example in the tropics, clove clusters do not ripen evenly and each tree is harvested five to eight times in the fruiting season. Clove clusters are picked when the unopened flower buds are full-sized, the calyx base has developed the characteristic pink flush, but no buds have opened or petals fallen to expose the stamens. The harvested clove clusters are taken to the storage centre and the stems, which are about 25% of the total dry weight, are removed and separated. Clovesare harvested by hand but modern orchards will have tractor-mounted platform pickers. Similarly the ylang ylang tree flowers throughout the year. The flowers, a source of essential oil, are gathered principally after the rainy season and during the dry season. At this time the flowers are drier, contain more oil and the oil is of higher quality. Flowers are harvested early in the day. Only fully developed yellow flowers are picked as green flowers produce poor quality oil. In order to avoid fermentation, the flowers should not be held in a mass and distillation should be undertaken as soon as possible.

In temperate environments flowering is seasonal and the stigma from theautumn flowering saffron crocus is an example of a flower-derived spice which has a specific harvesting time. , is the spice used to colour and flavour food There can be up to 12 flowers per corm which should be hand-picked daily, after the flower has opened but has not withered. The stigma is hand-separated or airflow-separated from the flower parts at the drying and processing facility.

2.2.4 Harvesting Roots and Rhizomes

Thecommon spices which are derived from roots, bulbs and rhizomes are turmeric, ginger, onion, garlic, horseradish and wasabi. Turmeric, a perennial herb grown as an annual crop, is ready for digging when the lower leaves turn yellow. The length of time to harvest maturity is dependent on cultivar. Hand digging is the most common form of harvesting the rhizomes although diggers and lifters can be used. The leaves must be cut prior to mechanical lifting or after hand digging. Care is necessary to avoid damage to the rhizome (splitting or bruising) as injuries can result in fungal infection and rejection. Rhizomes are lifted whole, washed, sun dried and the rhizome fingers (which are kept as seed material) are separated from the mother rhizome.

The harvesting of ginger, a perennial herb but often grown as an annual, depends on the cultivar and varies from 7-9 months for annual crops while perennial crops are harvested at the growers’ discretion. The time to harvest is also dependent on the projected end-use with fresh ginger with low fibre content harvested at about 190 days after planting. The harvesting method must ensure there is no rhizome damage and both manual and mechanical methods of rhizome digging are used. Some production areas use both methods by mechanically loosening the rhizomes to assist the hand lifting. Following lifting the rhizomes are washed, the roots removed and then killed by immersion in boiling water for about 10 minutes, dried and then stored.

The maturity of onions for harvest is based on top senescence when the bulb is converted from active growth to dormancy by under cutting and the beginning of the drying process. Garlic can be harvested at different stages of maturity for specialty markets but most commonly when the bulbs are well mature and the tops have dried completely. Horseradish, a perennial that is grown for its enlarged root, is ready for harvest after the leaves have been killed by frost. Horseradish that is harvested while it is still actively growing does not store as well.

2.2.5 Harvesting Bark, Wood and Resins

Many plants which are harvested for wood or bark products, are managed under coppice plantation systems. Cinnamon and Cassia production is an example of such a practice. Harvesting of the shoots is undertaken during the rainy season two years after coppicing. The selected shoots must have a uniform brown colour of bark and have at least two years growth. The rough outer bark of the selected shoots is first scraped off and the young tender inner bark is peeled off carefully from the stem. The inner bark curls naturally into the well-known quills. The best pieces of the peeled bark are packed with small pieces and tightly rolled to preserve the flavour and dried. The coppiced shoots are left for fermentation for 24 hours, dried in the shade for one day and in the sun for four days. The smaller quills are inserted into larger ones to form compound quills. The products are graded as quills, quillings, featherings, scraped chips and powders. The finest quality bark is obtained from shoots (<1.25 m by 1.25 cm diameter) with uniform brown thin bark harvested at six-month intervals.