Cultivating Carnivorous Plants (2015)

DROSOPHYLLUM

Drosophyllum lusitanicum growing in the Sierra Madrona.

NATCH GREYES

Drosophyllum lusitanicum,

the Portuguese Sundew, is an

unusual carnivorous plant.

Despite having a large, if

narrow range that stretches

along

the

coastline

Portugal through Andalusia,

Spain, and along the northern

Moroccan coast, Drosophyllum

lusitanicum was not formally

described

until

1806.

Although the single member

of the monotypic genus

Drosophyllum appears to be

closely related to the genera

Byblis and Drosera, in reality,

Drosophyllum is only very

distantly related to either

genera. In fact, Drosophyllum is

as closely related to Nepenthes

as it is related to Byblis and

Drosera.

Close photo of the leaves of Drosophyllum.17

Drosophyllum is unique among carnivores in that it inhabits dry areas close to the ocean. Nightly fogs

provide the plant with much of the moisture that it requires, but a deep root system also helps provide the

plant with some moisture. In summertime, Drosophyllum will experience weeks without rain. The essential

nature of the nightly fog is well documented in the native range of

this species. It only grows as far inland as the fog stretches.

The structure of the plant ensures that it captures as much of

the fog that condenses along its leaves as possible. The plant

generally consists of a single, central stem with a number of

narrow, triangular, almost pine-like leaves growing in a rosette

pattern from the central stem. These 8 to 16 inch (20 to 40

centimeter) long leaves point upwards, allowing moisture to run

down them towards the central stem. Water runs down the central

stem towards the root system. Dead leaves stay attached to the

plant and fall towards the ground, which allows the fog that

condenses along their length to run towards the root system.

The 16 inch to 60 inch (40 centimeter to 1.5 meter) tall plants

are often rumored to produce chemical inhibitors that prevent

other plants, especially members of its own species, from growing

too close. The field observations that led to this rumor probably

stem from observations at very harsh locations where there was a

high seedling mortality rate. At many locations, dozens of

Drosophyllum grow within inches of each other, something that

Drosophyllum with flower stalk

would be impossible if they really were producing chemical

emerging from the center of the plant.18

inhibitors.

CULTIVATING CARNIVOROUS PLANTS

In its native habitat, the bright yellow flowers have five petals and are produced in early spring, between

February and May. These self-fertile, one-and-a-half inch (four centimeter) flowers are produced in clusters of

three to fifteen. They open for several hours during the day. The pear-shaped seed matures in approximately

one month inside cone-shaped seedpods. Each seedpod contains between three and ten seeds. These are

dispersed by the wind and the seed germinates during the autumn rains, although seedpods can be stored for

many years with virtually no loss of viability. From seed, plants grow to maturity within two years.

In the wild , Drosophyllum grows in full sun and endures temperatures ranging from lows at 20° F (-7° C)

to highs of 113° F (45° C). Drosophyllum are often found in soil caught in sandstone crevices from sea level to

2,625 ft. (800 m) above sea level. Not many associated plants grow with Drosophyllum. The few Drosophyllum

that grow among shrubs and low-grasses are small and often underdeveloped. Drosophyllum are not ordinarily

observed growing in the shade of the native oaks.

In Cultivation

Drosophyllum in bloom in cultivation.19

NATCH GREYES

Some

authors

say

that

Drosophyllum is nearly impossible to

grow in cultivation. The problem

these authors face likely stems from

the most common misconception

about Drosophyllum: that it grows in

alkaline soils. There is no evidence

that the plant favors alkaline soils.

In fact, all the evidence points to

the fact that the plant is intolerant

of those soils.

Field observations reveal that

Drosophyllum does not grow in

alkaline soils, contrary to common

belief. In fact, Drosophyllum cannot

be found in limestone-based, i.e.

alkaline, soils in areas which appear

otherwise suitable for the species.

Observations revealed that the plant

prefers to grow in sandstone or

loam-based soils. Field pH tests run

on the loam-based soils have pH

measurements of around 5.3, solidly

on the acidic side. Sandstone-based

soils are thought to be similarly

Drosophyllum flower.20

acidic.

Despite literature suggesting that Drosophyllum can be propagated via leaf or root cuttings,

experimentation by many growers has revealed that the only reliable method of propagation is by seed. In

fact, evidence tends to suggest that propagation via cuttings is probably impossible.

The major difficulty in growing Drosophyllum stems from germinating seeds. Although seed placed on

suitable media germinates at a low rate after several months, higher germination rates can be achieved by

scratching the seed with a file or knife. Be careful not to cut into the white seed itself but only the seed coat.

Soaking the seed for 24 hours after scratching may help. Seed should then be sown scarified side down.

Germination occurs within three months.

My standard growing guide for Drosophyllum follows:

● Media: Drosophyllum should be potted in a very dry medium. I prefer one part perlite, one part

pumice, one part sand, and one part peat.

● Moisture: The easiest way to water Drosophyllum is via the tray method, but keep the tray dry most of

the time. It is possible to create a “double pot” wherein a small, typically clay, pot is placed inside a

larger pot filled with long-fiber sphagnum. The larger pot is placed in an ordinary tray of water, while

the smaller pot is filled with the regular Drosophyllum potting mix. This double pot method allows the

larger pot to wick water the Drosophyllum. In practice, scheduling infrequent watering sessions for a

single pot is probably easier than the double pot method.

CULTIVATING CARNIVOROUS PLANTS

● Humidity: In cultivation, Drosophyllum does not require high humidity. Although allowing the plant to

get water via fog is ideal, giving Drosophyllum lower humidity and water through the tray method is

better than keeping it in an environment with constant high humidity.

● Pot Size: Repotting is a major killer of Drosophyllum. Starting out the plants in biodegradable peat pots

is a good idea because it allows for successfully germinated plants to be potted out into bigger pots

without root disturbance. The idea pot size is at least one gallon and made of clay or another

permeable material, such as coco fiber.

● Feeding: Among all the carnivores, Drosophyllum appears best able to catch its own prey. Most

growers will be able to grow the species outdoors for the summer (and many can grow it outdoors in

spring and fall, too). Indoors, a weak orchid fertilizer mix every week or two works well.

● Temperature: Drosophyllum will tolerate a wide range of temperatures, but warmer is better. Generally,

days that do not fall below 60° F (16° C) or go above 90° F (32° C) are ideal for summer. In winter,

the plant should experience temperatures between 40° F (5° C) and 60° F (16° C).

● Dormancy: Drosophyllum goes through a cool, dry dormancy period in winter. Growth slows and

water will be needed less frequently.

● Propagation: The only reliable way to propagate Drosophyllum is via seed. As stated above, seed should

be scarified prior to sewing on a suitable media. Sowing the seed in a peat-heavy top layer in a

biodegradable seed starting pot is advisable. Doing so promotes soaking prior to germination, if in an

area where the soil medium will dry out quickly. Seedlings should be regularly checked for

dehydration and water added to the soil as necessary. Watering schedules should be adjusted to

become more frequent if seedlings regularly appear wilted. Older plants require less water.