Cultivating Carnivorous Plants (2015)

GROWING CARNIVORES INSIDE

A terrarium in the author’s living room.

Most carnivorous plants growers keep at least one carnivorous species inside. Like the outdoors, the

indoors also has many different environments, some of which are more suitable for growing carnivores and

others that are less suitable. Indoor growers need to assess their indoor areas for not only the plant’s basic

needs of water and light but also for humidity and temperature.

The most basic indoor set-up is a sunny windowsill. Many carnivores will do well on a windowsill. The

easiest way to care for them is to place them in a small plastic tray and to fill that with water, never allowing

the water to dry completely. This method of watering is called the “tray method.” East-facing windows are

good for plants that prefer cooler temperatures, while west-facing windows may allow for longer exposure to

the sun, depending on the location of the grower’s house. In the northern hemisphere, south-facing windows

CULTIVATING CARNIVOROUS PLANTS

will have the most ambient light. In the

southern

hemisphere,

the

north-facing

windows will have the most ambient light.

For more specialized carnivores, growers

often turn to terrariums. These can be

constructed of glass or plastic. For long-term

use, glass is preferable. For easier or younger,

plants, a terrarium on a windowsill works well.

Note, however, that a terrarium in direct sun

can heat up tremendously, causing a plant to

die due to heat stress. Therefore, any

terrarium should be accompanied by an in-

terrarium thermometer or tested with an out-

of-terrarium thermometer on a regular basis to

ensure that it is not becoming too hot for the

plants.

Once windowsill space runs out, growers

often turn to grow lights. These come in

several varieties, but most growers use either

florescent lights or LED lights. (It is also

possible to use metal halide, high pressure

sodium, or incandescent lights). The reason

for the widespread use of florescent lights and

LED lights is twofold: 1.) these types of lights

are cheaper to operate than other types, and

2.) these lights are widely available thanks to

recent advances in lightbulb manufacturing.

After running out of windowsill space,

An indoor setup using T5 lights (top) and LED lights

growers often have to find “grow racks.” Most

(bottom). LEDs often come in blue and red, rather than

growers use whatever shelving that they can

white, as is common with T5 lights. This is due to those

find. Oftentimes, these shelves are wire racks.

colors closer match to the photosynthetic wavelengths

These racks work extremely well for hanging

needed for plant growth.

light fixtures and running wires, but may be

prone to rusting.

In order to provide a stable base, most growers acquire a number of nursery trays, which they will place

atop the shelves and fill with water. Nursery trays are often made of thin plastic that becomes brittle over

time. I recommend investing in heavier plastic trays, made of rubberized plastic. These will outlast the

cheaper nursery trays by years, and, ultimately save money as they will not have to be replaced as often (or

suddenly spring leaks!).

Artificial Light Considerations

Until recently, most growers used any florescent lights that they could their hands on. Nowadays, most

use T5 lights, often in two-bulb or four-bulb arrays. There are innumerable companies that advertise their

bulbs and arrays as “grow lights” but, in reality, the key to good plant growth is the wavelengths of light and

its light intensity. The most valuable comparative measurement of lights is the Photosynthetic Active

NATCH GREYES

A typical indoor setup using an open terrarium, reflective Mylar, and 4-bulb, T5 light unit.

Radia

tion (PAR) value, i.e. the actual amount of energy being used by the plant for growth. This is not often

available on the packages of lightbulbs. In terms of actual information available on lightbulb packages,

including LEDS, the wavelength of the light produced by the lightbulbs is sometimes available. Chlorophyll

absorption peaks at 430 nanometers, 453 nanometers, 642 nanometers, and 662 nanometers.

When setting up a terrarium with lights, it is important to have a thermometer inside the terrarium.

Oftentimes, lights will be placed directly above the terrarium, which causes a lot of the heat produced by the

light array to enter the terrarium and heat it. In order to avoid some heat buildup and stagnant air, it is

advisable to have a small, computer-type fan inside the terrarium or to keep a lid a bit ajar.

Most species will prefer artificial light set on 8, 10, 12, or 14 hour cycles. Of course, the exact amount of

time artificial lights should be on depends on the strength of the lights. As a general rule, light loving species,

such as most Nepenthes, should exhibit beautiful colors under the lights. If colorful species are near maturity

and still, largely, green, light needs to be increased.

In addition to lightbulbs themselves, light may also be increased through the addition of reflective

coatings on the backs of terrariums or behind plants. The cheapest way to do this is to acquire “emergency

blankets” made of Mylar and cut those to fit behind the plants. While this will not significantly increase light

available to the plants, it will increase it enough to result in slightly better coloration.

CULTIVATING CARNIVOROUS PLANTS

Humidity Considerations

Terrariums are an easy way to increase ambient

humidity. Completely closed terrariums can increase

humidity to near 100%. Open terrariums can increase

terrariums 20% - 30% more than the outside air. How

much humidity needs to be increased dictates whether a

terrarium should be opened, partially closed, or

completely closed.

Many growers adapt aquariums into terrariums. The

advantages of aquariums are many. They are cheap. New

tanks can often be found for $1 a gallon, and used tanks

sell for even less. Glass shops, which can custom cut

tops, abound. These shops often charge around $20 for

a simple glass top for a 20 or 29 gallon tank, the size of

many collectors’ terrariums. Egg-crate for florescent

lights or live sphagnum can be placed on the bottom of

the terrarium to keep the plants from sitting in water.

Grow light fixtures are often sized to fit, almost exactly,

over the tops of aquariums.

Unfortunately,

aquariums

also

have

their

drawbacks. Tanks larger than 55-gallons often become

very expensive, and are priced much higher than their

component parts. Further, even 55-gallon tanks are

cramped for many species, once they get close to

maturity, as the tanks are often long and narrow, rather

than wider and taller. As a consequence, growers with

larger collections often turn to grow-tents, greenhouses,

or custom-built terrariums. All of these require some

level of technical expertise beyond the simple terrarium.

When possible, it is advisable to grow plants

outside of a high-humidity environment. For some A grow rack with both plants growing in the open

species, this is impossible, but, for many species, they

air (lighted) and plants growing in terrariums

can adjust to a lower-humidity environment. The

(dark). This mixed-use of grow racks is common

advantage of avoiding a terrarium is not just cost.

in larger collections which contain plants with

Avoiding a terrarium also prevents terrarium-specific

different humidity needs.

problems, such as stagnant air breeding fungus, from

occurring and harming one’s collection.