People who wish to grow lemon plants are encouraged to get them from nurseries or garden centres. Plants grown from seeds will take up to several years before they can mature and bear fruit, and techniques such as grafting and air-layering require a certain level of skill.

HOW TO GROW LEMONS

Buy a lemon plant that has flowers and fruit growing on it as this is a sign that the plant is mature.

Place the plant where it can get at least six hours of direct sunlight daily.

Apartment-dwellers growing the plant along corridors or in their balconies will be challenged by the lack of direct sunlight. And because lemon plants need space to grow well, the lack of it can also be an issue.

Plant it in the ground if possible. The soil should be loamy, well-drained and high in organic matter. It should be slightly acidic, with a pH level ranging between 5.5 and 6.5, so that the incidence of nutrient deficiency will be kept low.

In areas with poor soil conditions, the plant can be grown in a large pot with a diameter of at least 60cm and moved around to catch the sun.

Keep the root zone of the plant moist at all times.

A balanced fertiliser - where the proportions of nitrogen, phosphorus and potassium are equal - can be applied regularly to encourage healthy growth.

Use environment-friendly methods to deal with disease and pests, which can include caterpillars such as the larvae of the Lime Butterfly.

Another common pest is the citrus Hindu mite, which results in numerous small silver spots on the leaves of plants.

Summer or neem oil can be applied to help counter this, as well as manage the population of scale insects and mealy bugs - sap-sucking pests that can affect lemon plants.

Any leaves infested by leaf-miners, which are larvae that burrow in leaf tissues, should be promptly removed.

Plants can typically be kept disease-free if grown in well-drained soil in a sunny spot and are pruned regularly so air can circulate.

It can be hard to tell when a lemon fruit is ready to be harvested. This is because the fruit requires a temperature dip to take on a rich yellow colour.

In Singapore, where the temperature is relatively constant throughout the year, this might not happen. Citrus fruit do not ripen if they are harvested when immature.

• Source: Dr Wilson Wong, deputy director (horticulture) at the Singapore Botanic Gardens