RORIDULA - Cultivating Carnivorous Plants (2015)

Cultivating Carnivorous Plants (2015)


Roridula is a genus of proto-carnivorous plants that

has a mutualistic relationship with the two members of

the Pameridea genus, Pameridea roridulae and Pameridea

marlothii. Although each species in the genus Roridula has

sticky hairs like Drosera, neither produces digestive

enzymes. Instead, both rely on Pameridea, most often

Pameridea roridulae, to digest any prey that becomes caught

on their leaves and excrete nutrients. This mutualism

makes growing Roridula somewhat more difficult than

other carnivorous plants.

Both species of Roridula are commonly described as

woody shrubs, but large Roridula plants are more

accurately described as small pine trees with Drosera-style,

carnivorous needles. At maturity, Roridula dentata can

reach five feet (1.5 meters) tall. Roridula gorgonias is

smaller, only reaching 20 inches (50 cm) tall. Given

Roridula dentata’s immense size, it is not surprising that

occasionally a large plant will be spotted after having

snared a small bird.

The Fynbos of South Africa is the only place on

earth where Roridula can be found in the wild. Recently,

however, a fossilized member of the Roridulaceae family

was unearthed in Kaliningrad, Russia. This fossil,

preserved in amber, indicates that a very similar species

could be found all along the Baltic coastline 35 - 47

million years, when the region was a massive swamp.

Nowadays, both existent species live in this narrow

stretch of land along the Western Cape which

experiences cool, rainy winters and warm, dry summers.

Their native soil is, as with most carnivores, nutrient-

Roridula dentata with prey in cultivation at the

poor, and brush fires frequently clear the landscape.

University of Connecticut.



Although most of the rain in the Fynbos falls

in winter, both species of Roridula grow year-round.

In cultivation, they produce flowers in mid-winter

or early-spring, which is shortly before the plant

sees a burst of spring growth. The flowers are large,

showy, and pink. Roridula must be pollinated in

order to set seed, although cross-pollination is not

necessary. Seed is hard and fire-resistant. In fact, a

simulated brush fire is useful for germinating the

seed of both species, although it is only strictly

necessary for Roridula dentata.

In Cultivation

Neither species of Roridula is easy to grow.

Both can experience fungal attacks as a

consequence of stress, and both will easily succumb

unless the proper conditions are maintained and the





insecticides, and fertilizers are all barely tolerated, if

at all, and can easily be more damaging to Roridula

than the underlying pest or problem.

With both species of Roridula, the easiest and

surest way to propagate them successfully is via

seed. It is rare to obtain a Roridula plant in any form

other than seed, probably because of the difficulty

in germinating the seeds. For both species, the

seeds must be kept moist--but not wet--after

planting. It will take one to three months for the

seeds to germinate. If they have not germinated by

the three month mark, simulating a brush fire by

burning leaf litter atop their pot may be useful.

After germination, the seedlings can be repotted,

but care must be taken to avoid breaking the roots.

It is possible to propagate Roridula via cuttings,

but it is difficult to do and, generally, generates

weaker plants than those grown from seed. Cuttings

should be placed in the same type of media mixture

as adult plants after being dipped in a rooting

hormone. After potting, cuttings should be given

high humidity, but not stale air (as would occur in a

sealed plastic bag). Bottom heating will increase

likelihood of rooting.

Neither species of Roridula can survive

Roridula dentata in cultivation.

stagnant, humid air for more than a few hours. As a

This plant is over five feet tall!

consequence, it is probably not feasible to grow



either species in a terrarium due to the lack of fresh airflow. A mere few hours of stagnant, humid air can

result in the entire plant being overcome and succumbing to wilt and death.

Foliar fertilization can be of benefit to both species of Roridula, but it must be done carefully. A high

nitrogen, low phosphorous fertilizer, such as orchid fertilizer, is best, and should be lightly tested on a side

branch before the entire plant is dosed. An alternative to fertilization is to introduce Pameridea, but these can

be difficult to obtain.

Roridula dentata

The flower of Roridula dentata.38



Roridula dentata is native to the hot and arid inland South African mountains of Clanwilliam and Tulbagh

Ceres, centering on Cederberg. Plants are ordinarily found near streams and on moist slopes, which allow

them to access water via their deep taproots in times of little rain. The soils of these slopes are sandstone-

based, acidic with low levels of nutrients.




natives of the Finbos,

Roridula dentata is a

rapid grower, but it is

also a temperamental

grower. It will not do

well in conditions that

do not closely match

those of its native




gorgonias, which typically

grows along a single

stalk, branching only

after flowering, Roridula

dentata grows as a true

bush, and sends off

multiple branches from

its central trunk. This

branching tendency is

good news for growers,

as it provides them with

more opportunity to

The flower of Roridula dentata just beginning to open.39



feeding and conditions. It is not infrequently the case that a plant will suddenly have branches that begin to

turn brown and die. The reason for this is mostly likely the result of humidity being too high, light being too

little, or too much prey being captured. In order to prevent loss of the plant, the affected area must be

amputated before the rot spreads to healthy sections of the plant.

The easiest way to propagate Roridula dentata is via seed. The most successful way to get the seed to

germinate is to scarify the seeds with sandpaper. Then plant the seeds, half covered, in an appropriate media.

A brush fire must then be simulated, or, at least, the chemicals released by a brush fire must be introduced

into the media. The easiest way to do this is to burn some twigs and leaves on top of the soil, trapping the

smoke in a glass jar and holding it over the seeds for several minutes. Alternatively, one can purchase a

smoke-impregnated seed primer and use that to simulate a brush fire.

After simulating a brush fire, the pot should be kept in full sun, and the soil kept moist. After

germination, seedlings of Roridula dentata will grow quickly, sending a single taproot deep into the soil. As a

consequence, Roridula dentata requires a large pot. Clay is preferable. As the plant grows, watering should taper

off to the point of not watering for several days at a time, as with Drosophyllum.



Roridula gorgonias

Roridula gorgonias growing in cultivation at the Kew Botanical Gardens.40

Roridula gorgonias is native to the cool, humid area near the city of Hermanus, South Africa. As a

consequence, Roridula gorgonias prefers slightly cooler and wetter conditions than Roridula dentata. Perhaps the

easiest way to water Roridula gorgonias is via the tray method in summer, allowing the tray to dry completely

before filling with more water, but be careful not to overwater.

Unlike Roridula dentata, Roridula gorgonias does not require a simulated brush fire for its seed to germinate. A

simulated brush fire can, however, increase germination rates significantly. Growth of Roridula gorgonias is

slow, however, compared to Roridula dentata. This species grows at only half the rate of Roridula dentata.

My standard growing guide for Roridula is as follows:

Media: A mixture of one part sphagnum peat and one part sand seems to work well.

Moisture: Watering via the tray method and allowing the water to evaporate and stay evaporated for a

while between each watering is probably easiest. Roridula dentata should be kept drier than Roridula

gorgonias. Aim for as dry as Drosophyllum for Roridula dentata.



Humidity: Humidity should be kept low, and the air should not be allowed to become stagnant for

either species of Roridula.

Pot Size: Pots should be made of clay, if possible, and around 1 gallon in size. Roridula dentata requires

a larger pot than Roridula gorgonias.

Feeding: A high nitrogen, low phosphorous fertilizer diluted to quarter strength and applied to the

leaf may work, but should be tested on a small portion of the plant before being applied to the whole


Temperature: Temperatures should be kept above freezing and below 95° F (35° C).

Dormancy: Dormancy is not required for Roridula.

Propagation: Roridula is most easily propagated through seed, but it can also be propagated through

leaf cuttings. The best method for propagating each species Roridula is discussed below.