Direct sowing is not recommended because crop development is delayed in comparison to crops established from grafted transplanted seedlings. In addition, direct sowing plants have greater variability in vegetative growth, maturation, disease tolerance and other important aspects of crop performance including plant longevity.
Rubber tree seeds complete germination 10-15 days after sowing and produce
hypogeal seedlings. Vegetative growth is vigorous and the adult plant is a tree 25.0 m to 40.0 m high. The primary tap-root is 5.0-10.0 m long and lateral roots usually reach 6.0 m to 9.0 m in lateral growth. Leaves are alternate and trifoliate.
(8) Flowers are monoecious and are found in raceme inflorescences. Flowering and subsequent seed production show wide annual variations in quantity and quality as a result of heavy rains and intense winds that may increase disease pressures causing young fruits to shed or abort prematurely. Flowering usually occurs from August to October in the spring in the Brazilian southeast. Flowering is also negatively affected by water deficits. As a consequence, possible variations in crop performance during the flowering period permit an estimate of crop yield potential.
(9) Fruit development continues during the warm, rainy season which occurs during the Brazilian summer. The mature fruit is a dehiscent capsule usually containing three seeds. The opening of the dry fruits occurs during late summer.
(10) Rubber tree seeds possess a brilliant spotted coat showing a prominent caruncle and usually are globate in shape. Significant seed production starts four years after crop establishment and mature seeds are shed for approximately five months after flowering.
(11) Climate Conditions
Temperature and relative humidity are the most important climatic conditions affecting plant developmental stages, latex production and seed yield. Regions with mean annual temperature lower than 20oC and high humidity are not optimum for rubber tree establishment because disease pressures are intense. Temperatures from 27oC to 30oC are the most favorable for rubber tree growth.