Passionfruit grows well in tropical and subtropical regions, where the climate is hot and humid. Temperature, relative humidity, light intensity and precipitation have an important influence on the longevity and the yield of the plants, but also favor the incidence of pests and diseases.
Biological processes, such as flowering, fertilization, fruit formation, maturation and fruit quality depend on temperatures. The temperature range between 21 and 25°C is considered as the most favorable for the growth of the plant, being best between 23 and 25°C, but passionfruit is being successfully cultivated in temperatures between 18°C and 35°C. Lower temperatures slow the growth of the plant and reduce the uptake of nutrients and fruit production, while very high or very low temperatures affect fruit bearing. At intermediate temperatures of 23°C to 28°C, the fruit growth period is 60 days, when the temperatures were lower (23°C) and higher (33°C) the period was 75 days. The germination period of the seeds is shorter in summer time than in the coldest months, when the period is longer.
Growing passionfruit at altitudes between 100 m and 1,000 m is recommended. Plantations at lower altitudes last for a shorter period of time than those with higher altitudes. In South Africa, at altitudes between 1,200 and 1,400 m, plantations may be productive for eight years, owing to the longer cycles, implicating a greater longevity.
Relative humidity has a great influence on vegetative development and the phytosanitary state of the passionfruit. Air relative humidity of around 60% is the most favorable for the passionfruit. Elevated temperature, associated with constant wind and low relative humidity, causes a drying out of the tissues by excessive transpiration and impedes the development of the passionfruit. Relative humidity of greater than 60%, when associated with rains, favors the incidence of disease, like citrus scab and anthracnose (black spot) in the aboveground parts of the vine.
The susceptibility of passionfruit to strong winds is also an important factor for this crop. Besides direct damage to the plant, it has to adapt its conduction systems. Strong winds cause plants to fall and cold winds cause flowers and new fruits to fall, as well as delay plant growth. In regions prone to high winds the use of windbreaks, like bamboo, grevillea, pine, hibiscus, eucalyptus and grass species is indispensable.
Light is an important factor affecting growth due to its effects on photosynthesis. An increase in the hours of daylight results in greater photosynthetic activity, with an increase in the plants vigour and the size and quality of the fruit. Inadequate light affects the formation of the flowers and fruit. Regions in which the day length is greater than 11 hours have the best conditions for flowering. In the winter months, the plants do not flower because the days are shorter. In the semi-arid regions of Brazil, with more than 11 hours of day light associated with high temperatures throughout the year, the passion flowers continuously producing fruits throughout the year, as long as there is an adequate supply of water. Light intensity greatly influences the phenological phenomenon of flower opening in the yellow passionfruit. The flowers normally open at 12.00 hrs, immediately following the maximum incidence of photosynthetically active radiation (PAR), and close at 15.00 hrs; however when light intensity is lower, they close at 14.30 hrs.
Passionfruit develops continuously and so needs a constant supply of water. The demand for water varies from 800 to 1750 mm and must be well distributed throughout the year, preferably with 60 to 120 mm of water each month, by rain complemented when necessary with irrigation. Generally, annual rainfall should be at least 900 mm. It is reported that annual rainfall in passionfruit growing areas of India ranges between 1000-2500 mm. Although the plant withstands droughts relatively well, prolonged drought damages its vegetative development, causing, in severe cases, leaf fall and the formation of smaller and lighter fruits. On the other hand, intense rains in the flowering period also damage production, because they inhibit pollination by diminishing the activity of pollinating insects and causing pollen grains to burst. In regions where the rains occur in specific periods, resulting in shortage for a few months, irrigation is indispensable to guarantee good production and fruit quality.
