Here are the explanations for some of the most common problems:
Failure to flower: Lack of light, lack of feeding, erratic watering, or low temperatures can all cause this problem. If a citrus plant is grown from pips it will often not fruit for a number of years as they have to go through a juvenile stage before flowering. An average time for trees grown from seed to fruit is seven to ten years. Commercially, citrus are propagated by budding or This involves joining the roots of one plant to the stem of another related plant, so they fuse together to form one plant. There are various methods, all requiring great skill. Grafting is mainly carried out by commercial growers to combine one plant’s qualities of flowering or fruiting (the upper section or scion) with the vigour or resilience of the other (the roots or rootstock). Fruit trees are often grafted, along with a few ornamental shrubs and trees, and in recent years grafted vegetable plants (mainly tomatoes, but also chillies, cucumbers, aubergines, etc) have become available.
Flowers fall before fruit sets: Dryness at the roots and lack of air The concentration of water vapour in the atmosphere. This affects the rate at which plants transpire (lose water from their leaf pores), which in turn affects how much water their roots absorb from the soil. If air humidity is low, plants transpire quickly and become at risk of wilting if water is lost from the leaves faster than it can be absorbed by the roots. Different plants require different levels of humidity to thrive. Many tropical houseplants need high humidity and are best grown in a steamy bathroom, misted regularly or placed on a saucer of damp pebbles. In a greenhouse, humidity can be raised in hot weather by damping down (wetting) the floor or overhead misting.
Yellowing of leaves: There are several possibilities. The roots could be too wet or too dry. Draughts, low temperatures, or lack of feeding will also result in yellowing leaves.
Loss of leaves: This can be caused by draughts, too low or high temperatures in winter, often coupled with too much water in winter. Citrus prefer a cool winter rest. Provide lemons with a minimum winter night temperature of not less than 10°C (50°F) and calamondin oranges with 13°C (55°F).
Fruit fall: Fruits should ripen in a period of warm sunny weather, taking almost a year to develop to full size. Most cultivars set too much fruit for the size of the plant. Some of these will be shed, or clusters should be thinned to one fruit each on young plants.
Rotting roots: The first sign may be leaf fall or yellowing often caused by overwatering. Cut away damaged roots with some of the Can refer to either home-made garden compost or seed/potting compost: • Garden compost is a soil improver made from decomposed plant waste, usually in a compost bin or heap. It is added to soil to improve its fertility, structure and water-holding capacity. Seed or potting composts are used for growing seedlings or plants in containers - a wide range of commercially produced peat-free composts are available, made from a mix of various ingredients, such as loam, composted bark, coir and sand, although you can mix your own.