Litchis, often known by their other name “lychee,” hail from the subtropical regions of China, where they have been cultivated for over 2000 years, treasured for their sweet, fragrant flavour. The fruit is a member of the soapberry family, which includes other well-known fruits like rambutan and longan. The litchi has a storied history, steeped in the luxury and sophistication of ancient Chinese imperial courts, where it was a coveted delicacy. Its popularity as a symbol of romance and love in Chinese culture has persisted through the centuries. From its origins in the provinces of Guangdong and Fujian in China, the cultivation of litchi spread over time throughout Southeast Asia and, eventually, across the globe.
Litchi fruit
Thriving in a warm, humid climate, litchi trees found a favourable environment in the subtropical and tropical regions of the world. They require a distinct dry and cool period for the successful development of flowers and fruits, which aligns with the climatic conditions of subtropical zones. In modern times, litchi orchards can be found in many parts of Asia, as well as in the United States, particularly in Florida and Hawaii, South Africa, Australia, and Central and South America.
The spread of the litchi is a testament to humanity’s fascination with the fruit’s unique taste and texture: a translucent, aromatic pulp encased in a rough, leathery skin and a single, glossy seed. Today, litchi continues to be celebrated for its exotic appeal and is a staple in tropical and subtropical fruit agriculture.
Botany and Taxonomy
The litchi (Litchi chinensis) is a medium-sized evergreen tree notable for its delicious fruit and attractive foliage. Botanically, the fruit is classified as a drupe, and the tree itself belongs to the Sapindaceae family. Its compound leaves are pinnate, usually with four to eight leaflets, which are glossy and leathery in texture. The tree blooms with small, greenish-white to yellow flowers, which are pollinated by bees and other insects. The development of the fruit from flower to harvestable drupe is a complex process influenced by various environmental factors and will be explored in detail in subsequent sections.
The taxonomy of the lychee places it within the genus Litchi, in the family Sapindaceae. It is the sole member of its genus, with the species name ‘chinensis’ reflecting its Chinese origin. Within South Africa, the genetic diversity of lychee has been enriched through selective breeding and the introduction of different cultivars. These cultivars have been chosen for their adaptability to the South African climate, disease resistance, and fruit quality. Cultivars such as ‘Mauritius’ and ‘McLean’s Red’ are among the popular varieties in South Africa, each with distinct genetic characteristics that affect fruit size, flavour, and harvest time. South African lychee production benefits from these genetic variations, allowing for a range of harvesting seasons and market preferences. Research into the genetics of lychee aims to further optimise these traits to ensure the sustainability and profitability of the lychee industry in the region.
Taxonomy of litchi.
|
Scientific Classification |
|
|
Kingdom |
Plantae |
|
Phylum |
Angiosperms |
|
Class |
Magnoliopsida |
|
Order |
Sapindales |
|
Family |
Sapindaceae |
|
Genus |
Litchi |
|
Species |
L. chinensis |
Ecology
Litchis, including the well-loved Litchi chinensis, are subtropical evergreens that flourish in regions where the climate offers cool, dry winters and warm, humid summers – a climate profile well-suited to certain areas in South Africa. The trees are not only favoured for their delectable fruit but also their lush foliage, contributing both to biodiversity and to the aesthetics of the landscape.
A. Soil
In South Africa, litchis thrive in a variety of soil types, provided they are well-drained to avoid waterlogging, which can be detrimental to the trees. The soils ranging from alluvial silty loams to clays, common in the Pearl River delta of China where litchis originate, find their parallel in the rich soils of South Africa’s litchi-growing regions. These soils are often slightly acidic, with a pH ranging between 5.0 and 6.5, ideal for litchi cultivation.
B. Climate
Litchis require a specific range of temperatures for optimal growth. While young trees are sensitive to frost and can be damaged or killed at temperatures of -2 to -3°C, mature trees display more resilience. The subtropical climate of South Africa provides a period of cold needed for flowering, rarely dropping below freezing, which is conducive to the litchi’s ecological needs. Litchis require plenty of sunlight for energy and photosynthesis. Shading can reduce the number of panicles a tree produces and the overall yield. South Africa’s clear skies and ample sunlight, especially in summer, are beneficial for litchi trees, ensuring good photosynthetic activity.
High rainfall and humidity are favourable for litchi growth. South African litchis are often grown in areas with adequate annual rainfall, around 1250–2000 mm. However, during the dry autumn and winter seasons, irrigation becomes critical to prevent vegetative growth and encourage flowering. In windy regions, windbreaks may be necessary to protect the litchi orchards. Strong winds can damage branches, flowers, and emerging fruit, so strategically placed barriers can help reduce wind impact.
Morphology and Characteristics
A. Litchi Trees
Litchi orchard in South Africa
Litchi trees are evergreen, reaching heights of 10-12 meters under favourable conditions. They are characterised by their spreading canopy and slow growth rate. The trees have a long lifespan, with some cultivars known to thrive for several centuries. The branching pattern of litchi trees varies among cultivars. Some exhibit a broad spreading habit with low-hanging branches, while others have more upright branches forming a compact, rounded canopy. The branches tend to be brittle, making them vulnerable to damage from strong winds. The leaves of the litchi tree are pinnately compound, usually featuring two to five pairs of leaflets. These leaflets are elliptical to lanceolate in shape, measuring 2.5–6.4 cm in width and 7.6–17 cm in length. The colour of the leaves ranges from deep green in mature foliage to pale green, pinkish, or copperish red in new growth flushes.
B. Inflorescence and Flowering
A litchi tree in bloom
The litchi tree produces its flowers on terminal panicles. These panicles can either be leafy or leafless and are well-branched, supporting a profusion of small flowers. The flowering period varies depending on the cultivar and environmental conditions, but typically, it begins in late autumn and can extend to early spring. Litchi flowers are small, typically 3.0–6.0 mm in length, and appear in shades of yellow-green or brownish-yellow. They are apetalous (lacking petals) and consist of small valvate sepals, a fleshy disc, and multiple stamens. The litchi flowers are unique in their sexual configuration, with three distinct types:
- Type I: Functionally male, abundant in pollen but lacking in ovule differentiation.
- Type II: Morphologically hermaphrodite but primarily functioning as female, with a well-developed pistil and stamens that are typically sterile.
- Type III: Morphologically hermaphrodite, functioning as male, with a rudimentary pistil and viable pollen grains.
A magnified image of individual litchi flowers
C. Pollination and Fruit Set
Pollinated flowers with early fruit set
Litchi trees often exhibit a degree of self-sterility, necessitating cross-pollination for an effective fruit set. Bees, particularly the species Apis and Mellifera, are major pollinators. The pollination process is facilitated by the tree’s staggered flowering cycle, where male and hermaphrodite flowers open at different times, ensuring cross-pollination.
D. Fruit
Parts of a litchi fruit.
The development of litchi fruit from pollination to maturity is a process that spans approximately 80 to 112 days. The fruit, which is botanically a drupe, undergoes three distinct growth stages:
- Initial Growth Phase: Characterised by rapid enlargement of the fruit.
- Seed and aril development: The seed initially dominates the fruit’s internal space, but as the aril (edible portion) develops, it becomes the primary component of the fruit.
- Maturation: Involves the accumulation of sugars and reduction of acidity, leading to the fruit’s characteristic sweet and tart flavour.
Litchi fruits are known for their unique and appealing taste. The outer skin is rough, leathery, and usually red or pink when ripe. The edible part of the fruit is the translucent, juicy aril that surrounds a single, large seed.
Cultivars and Distribution
In South Africa, litchi cultivation is centred around a select few cultivars, each chosen for its unique traits that cater to local agricultural and market needs. ‘Mauritius’ is particularly favoured for its reliable fruiting and excellent fruit quality, marked by a high flesh-to-seed ratio and large fruits. ‘McLean’s Red’ is another sought-after cultivar, known for its early maturation which allows farmers to benefit from early season markets. Its fruits are characterised by a vibrant red hue and a sweet taste. ‘Fay Zee Siu’ (Feizixiao) also enjoys popularity, mainly for its large size and sweet flavour, coupled with its adaptability to various climatic conditions.
A ripe cluster of Mauritius cultivar litchis
Litchi cultivation in South Africa is primarily focused in the subtropical regions, benefiting from the favourable climatic conditions these areas offer. The Limpopo Province, known for its warm and frost-free climate, is a significant contributor to the country’s litchi production, particularly in and around Tzaneen. This region alone accounts for approximately 38% of South Africa’s litchi output. Following closely is the Mpumalanga Province, especially notable are the towns of Nelspruit, Hazyview, and Malelane. This area, with its hot Lowveld region, contributes about 60% of the national production, thanks to its suitable environment characterised by ample rainfall and warm temperatures. KwaZulu-Natal Province also plays a role in litchi farming, especially in its coastal areas, which offer a humid, subtropical climate conducive to litchi growth.
In 2016, the total area planted with litchis in South Africa was reported to be 1,124 hectares. This is a small fraction compared to the global scenario, where about 96% of the world’s litchi production comes from the Northern Hemisphere. China, Taiwan, Vietnam, Thailand, and India are the major producers, with China alone contributing to about 70% of the global supply.
A. Breeding Objectives
The objectives of litchi breeding programs are multi-faceted. Firstly, there is a significant emphasis on improving fruit quality. This includes enhancing the taste, size, and appearance of the litchi fruits, ensuring they meet both local and international market standards. Secondly, the programs prioritise the development of cultivars that exhibit natural resistance to prevalent pests and diseases, which is critical in reducing reliance on chemical pesticides and enhancing sustainable farming practices. Lastly, an important goal is to breed litchi varieties that are resilient to climatic changes. With the increasing unpredictability of weather patterns, developing cultivars that can withstand such variations is key to ensuring steady and reliable litchi production.
B. Breeding Challenges
Despite the clear objectives, litchi breeding in South Africa faces several challenges. A major issue is the limited genetic diversity, as the number of litchi cultivars available outside its native Asian region is relatively small. This limitation poses a risk of reduced adaptability and susceptibility to diseases. Another challenge is the inherently long juvenile phase of litchi trees, which delays fruit production and extends the time frame for assessing the success of new cultivars. Additionally, the complexity of litchi’s flowering and pollination process presents difficulties in achieving consistent breeding results. These challenges necessitate ongoing research and innovative approaches to ensure the successful development of new and improved litchi cultivars.