Eucalypts in South Africa

The Eucalypts are the world’s most valuable and most widely planted commercial plantation tree genus. Discover why and how with Sappi in South Africa in this FAQ.

What are Eucalypts?

Eucalypts are a group of trees belonging to the Myrtaceae (myrtle) family, containing the genera Angophora, Corymbia and Eucalyptus. Eucalypts are generally long-lived, evergreen angiosperm plants that flower and form fruits with seeds. However, the flowers have no petals. Instead, the bloom consists of hundreds of stamens. The seeds are enclosed in a dry or woody fruit that develops from the ovary within the flower. Many eucalypts, but not all, are known as ’gum trees’  because they exude copious amounts of sap from any break in the bark.

What are hybrids?

Hybrids are the result of crossing two different taxa through sexual reproduction. Sappi produces several inter-specific (between species) hybrids, including Eucalyptus grandis x Eucalyptus nitens (often referred to as ‘GN’) and Eucalyptus grandis x E. urophylla (GU). 

Where do Eucalyptus trees come from?

The eucalypts originate predominantly from Australia, where they grow in a wide variety of climatic regions, ranging from deserts to swamps to mountainsides – hence their environmental plasticity. Four species of Eucalyptus (E. deglupta, E. orophila, E. urophylla and E. wetarensis) originate outside Australia in Indonesia, the Southern Philippines and New Guinea. Eucalypts are thus not indigenous to South Africa and are classified as exotic species.

What characterises the Eucalypts?

There are over 700 species of Eucalyptus that exhibit remarkable diversity across their native range. Developmental characters such as bark, leaf and inflorescence type, ability to make epicormic shoots, adaptation to fire damage, as well as tremendous chemical variation underlying herbivore defence, vary within, and between, groups. The Eucalyptus genus includes species with very fast growth rates (mean annual growth rates of up to 20-35 m3/ha/year), allowing many varieties to reach maturity as early as ten years in comparison to other hardwood species that can take 18-25 years to reach early maturity. 

Do Eucalypts have any disadvantages?

Living Eucalypts are prone to biotic and abiotic stresses. This includes susceptibility to numerous pests and diseases, evidenced by the presence of stem cankers, root rot, foliar wilting and necrosis that can impact survival and growth. Abiotic stresses caused by environmental factors can also result in growth stresses, which affect yield. Productivity can be enhanced with effective risk management strategies, such as genotype-by-site matching, maintaining genetic diversity, breeding for resistance, and reducing stress caused by negative impacts such as drought, frost, snow, pest and diseases.

What value do Eucalypts offer? 

The diversity within the eucalypts has been the basis of a multitude of uses, including timber, pulp, lignocellulosic biomass, oils, and ecosystem services. Some of their key uses include: 

  • Cellulosic fibre. Some eucalypt species are very good for kraft pulping and dissolving wood (DP) pulping. Both Saiccor and Ngodwana Mills use eucalypts to manufacture Verve. This is a purified cellulose pulp suitable for subsequent chemical conversion into a range of products. DP with 91-95% cellulose content is mostly used to make viscose fibres for use in textiles. Higher cellulose content DP is used to make rayon yarn for industrial products such as the cord used in tyres, rayon staple for high-quality fabrics, acetate and other speciality products.
  • Biorefinery applications. At Sappi, we make the most of every tree harvested, including the extraction of sugars for various purposes including the production of xylitol – widely used as a sugar substitute – and furfural, used mainly for resins.
  • Bioenergy production. Eucalypts are also receiving attention for bioenergy because most of the extracted lignin can be used in recovery boilers for energy production.
  • Medicinal value. Eucalyptus oils derived from the leaves of about a dozen Eucalyptus tree species are used for therapeutic and medicinal purposes. Medicinal effects are primarily due to a chemical compound called eucalyptol (or cineole). Eucalyptus oil is packed with numerous natural compounds that work in synergy to produce a variety of health-promoting effects, from relieving cold symptoms to reducing pain or cleaning cuts and scrapes.