Growing Nepenthes in a Completely
Keywords: cultivation: Nepenthes, planting media.
Nepenthes are usually planted in mixtures incorporating
organic matter such as peat, pine bark, Osmunda fiber, Sphagnum,
etc. While these materials produce good results, they have disadvantages.
Most of the ingredients decompose rapidly, and the result is a compressed
substrate that inhibits air circulation among the roots. As a consequence
the plants have to be repotted frequently. This means extra expense and
work for the grower, and in almost every case, a temporary cessation in
growth of the freshly repotted plants which lasts until the disturbed
roots acclimatize. Another problem is that the use of peat directly contributes
to destroying the wetlands where it is quarried. The destruction of habitat,
in turn, is the main reason for the disappearance of many carnivorous
plants. Because of these disadvantages, new planting media are always
In the wild, some Nepenthes species are found
growing in inorganic soils. For a few examples, N. danseri, N. neoguineensis,
and other species from New Guinea and the Philippines grow in lateritic
soil (see Back Cover), N. eustachya grows in bare rock (Figure
1), N. lavicola thrives in volcanic rock, and N. madagascariensis
lives in quartz sand. These observations suggest that it may be possible
to grow Nepenthes in inorganic media.
Rockwool is commonly tried as a non-organic planting
material. In spite of limited success with some Nepenthes species,
this method is not favoured because of health risks associated with handling
this stuff. In two papers, Feßler (1982, 1986) described growing
Nepenthes in lava-clinkers. He attributed his successes with lowland
species to the available N, P2O5, K2O
and Mg the lava contains, and also to the fact that it has the ability
to store up to 20% water by volume. From this description an alternative
potting mix was developed, which works for all sixty Nepenthes
species tested--lowlanders and highlanders alike. Even species such as
N. ampullaria and N. bicalcarata do well, even though they
often grow naturally in peat swamps.
The mixture consists of one part each: Seramis®
clay perls (Effem, Verden/Aller), lava gravel (sold in aquarium shops,
grain size approximately 1 cm), Lecaton® (expanded clay
perls used for hydroponics, grain size approximately 1 cm) (Figure 2).
These ingredients have the advantage of being more widely available than
lava-clinkers. The mixture is slightly alkaline with a pH of 7.2, and
should be soaked in purified water before being used.
Table 1. Advantages and disadvantages
of the new inorganic potting mix.
1) Moistens easily, even when completely dry.
2) Compresses/degrades slowly (repotting is less frequent).
3) Airy mix is optimal for the roots.
4) No peat or Sphagnum is required, so habitat destruction
is not promoted.
1) Heavy (adding one part Styrofoam chips may help).
2) Initial cost is higher.
Potting Plants with Inorganic Mix
The best pots are plastic baskets commonly used for cultivating
water lilies. These baskets promote air circulation near the roots. They
are available in square and round shapes, and the round ones are best
used as hanging baskets. Conventional plastic pots may also used, especially
for smaller plants.
The potting procedure is as follows. Remove the plant
from its old pot, and remove all the old substrate from its roots by submerging
it in a bucket of purified water. This decreases the chance of residual
organic material, caught in the roots, of rotting. Put a layer of the
potting mix in the new pot. Plant the specimen in the middle of the pot,
filling the pot with the inorganic potting material. Immerse the whole
pot in purified water, at room temperature. Plants grown in organic soil,
repotted into the inorganic mix, show almost no interruption of growth.
Repotting plants already grown in inorganic substrate
is even easier (although this is rarely a necessity!). The roots easily
separate from the substrate, and are ready for repotting.
Watering can be done by immersing the entire pot, or
from above until water drains from the pot. Both methods serve to provide
the plant moisture as well as to leach accumulated salts out of the planting
medium. As long as the pots do not sit in water, it is impossible to overwater
The water quality is of great importance. If your rainwater
is polluted or contaminated, use reverse osmosis water.
It is necessary to fertilize your Nepenthes because
this planting medium does not contain decomposing organic matter. Slow-release
fertilizers such as Osmocote® 16-8-12(-2) (i.e. 8.3% N
from NH4 + 7.7% N from NO3, 8% P from P2O5,
12% K from water-soluble K2O and 2% Mg from MgO) are preferred.
One third of the amount suggested on the label is enough for Nepenthes.
The fertilizer is best mixed with the substrate before potting. At six-month
intervals, add the same amount of fertilizer onto the top of the pot.
Cuttings root exceptionally well in the substrate. They
are directly planted in the substrate, (with or without rooting hormones),
and are treated like rooted plants. If the cuttings have pitchers, add
water to them. The substrate is too coarse to be used for sowing seeds.
Use pure Seramis® or fine vermiculite instead.
The medium is very good for the acclimatization of sterile
grown (i.e. tissue culture) Nepenthes. After removing the agar
sticking to the plants, pot them in clear plastic boxes containing the
substrate. Maintaining a relative humidity of almost 100% is most important
during the first two weeks. Afterwards, the plastic cover is removed and
the plants are treated like adult plants. Since the substrate can be autoclaved,
the plants may be kept sterile or at least minimally contaminated by troublesome
moulds during the beginning of this weaning procedure. Figure 3 shows
a specimen of N. sumatrana two years after planting it out. When
weaned it had a diameter of only 5 cm!
The described results are all obtained growing Nepenthes
in terrariums of varying sizes with artificial lights (cool white fluorescent
lamps or high pressure mercury lamps). Modifications of the methods described
may be necessary to adapt them to greenhouse conditions. Nevertheless,
hopefully many other growers are encouraged to experiment and report on
their results in the future.
Feßler, A. 1982, Nepenthes in Lava-Schlacke,
Dt. Gartenbau, 36, 1643-1644.
Feßler, A. 1986, Nepenthes in Lava-Schlacke,
Das Taublatt, 3 (6), 6-8.
Back Cover: N. danseri growing in laterite gravel.