In the wild, Nepenthes thrive in nutrient-poor soil largely because they are capable of supplementing their diet with insect prey. Though it has been shown that plants in cultivation can survive for many years without "eating", growth can be greatly enhanced by regular feeding. In some situations, such as outdoors or in the greenhouse, the plants may capture a sufficient number of insects on their own. Many growers prefer to feed insects to the pitchers by hand; in this case frozen crickets or mealworms (available at pet food stores) are often used. Care should be taken to avoid an excess amount of prey in the pitchers, as this can lead to bad odours and death of the pitcher. Usually a few insects per pitcher is sufficient. Foodstuffs such as meat and eggs can lead to rot. As an alternative to feeding with insects, Nepenthes may be given artificial fertilizers. A variety of brands can be used, but those with a high nitrogen content and full micronutrients give the best results. Fertilizer (usually diluted to 1/4 normal concentration) can be applied directly to the soil once monthly to mature, actively-growing plants. Young plants or slow-growing species (especially highlanders) should be given a more dilute solution at less frequent intervals.
The vine-forming habit of most Nepenthes species necessitates regular pruning if the plants are to be kept in good form. Pruning can be performed year-round in tropical areas, or in spring when the plants have resumed active growth. Generally, most or all of the long climbing stems can be trimmed back; this will encourage the development of new robust basal shoots and stimulate the formation of lower pitchers. It is important not to remove all the leaves, as there needs to be sufficient foliage remaining for the plant to recover vigorously. Plants which are cut back completely to the soil will often die.
Pitcher production is a good indication of general plant health; plants are unhealthy or are kept in poor conditions will often fail to produce pitchers. Even healthy plants do not necessarily produce a pitcher on each leaf and some species appear to produce pitchers only in intermittent flushes. Pitcher formation can be encouraged by good lighting and high humidity. In some species, upper pitchers are more regularly produced on tendrils which have actively coiled around an object. Though there is some evidence to indicate that water-stressed plants are capable of reabsorbing moisture from their pitchers, severely dehydrated plants may suddenly drop their pitchers. Developing Nepenthes pitchers will secrete their own fluid, and it is usually unnecessary to add water to them as this may dilute the contents and render them ineffective for digestion. Exceptions can be made for those species with reclining lids such as N. ampullaria and N. lowii, or if the pitcher contents have been accidentally spilled.
Pests & Diseases
Nepenthes are generally pest-free, though a few insects will sometimes present problems in collections. Wherever possible it is best to remove pests by hand rather than treating with insecticides, as frequent use of some chemicals can result in severe damage to the plants.Thrips are a common pest in many cool greenhouses and will occasionally attack Nepenthes, though they seldom occur in sufficient numbers to present a serious threat. They can be found most often on the undersides of the leaves near the midrib, and can easily be removed by regularly wiping the leaves clean. Scale, which are often introduced to the plants by ants, can present a much more severe problem. Though scale can sometimes be kept in check by diligent hand-picking, infested plants may need to be treated with an insecticide. For severe pest problems the use of a proprietry spray may be necessary.