Dewy pine

What they are

The dewy pine is one species, Drosophyllum lusitanicum, alone in its genus and, in current classifications, in its own family, the Drosophyllaceae; older works keep it in the sundew family. A tuft of narrow leaves 15 to 20 cm (6 to 8 in) long, the width of a pine needle and grooved down the top, rises from a short woody stem, and each new leaf unfurls from a coil that faces outward, the reverse of a fern frond. After a few years the plant becomes a small, sparsely branched subshrub, 45 to 90 cm (18 to 35 in) tall in the wild. The whole leaf, apart from the groove, is studded with stalked glands tipped with drops of mucilage. Darwin described the glands as pink or purple, like miniature mushrooms, and unable to move.

The trap works without movement. The mucilage smells of honey and the leaves carry ultraviolet patterns that insects see, so flies land, and the drops come away from the gland onto the fly rather than holding it in place. A struggling insect picks up drop after drop until it is coated, sinks onto the leaf and dies there on a second set of tiny stalkless glands that pour out digestive enzymes. The glands secrete all the time, whether or not anything has been caught; Darwin found that a plant under a wetted bell-glass dripped with fluid within a day. In the wild a young rosette of ten leaves can carry more than a hundred insects, mostly flies, and a third to two-thirds of the plant’s leaf nitrogen comes from prey. The flowers are bright yellow, about 2.5 cm (1 in) across, open in spring and set seed by themselves; the seed ripens by late summer.

Where they grow

Drosophyllum is native to western and southern Portugal, south-western Spain and the north of Morocco, and nowhere else. It grows on dry, open heathland among heathers and rock roses, on acid, nutrient-poor soils weathered from sandstone and always on ground that never waterlogs. Measured soil pH at wild sites runs from about 3.7 to 5.3, with a few populations on near-neutral soil over sandy limestone where little calcium is available to the plant; it is not a lime-lover, and the mineral mix growers use is for drainage, not alkalinity. The climate is Mediterranean, with wet winters and summers of up to three months without rain, when the topsoil can pass 40 °C (104 °F). At night sea fog and dew condense on the sticky leaves and the glands absorb some of that water. The root is a short, woody, heavily lignified taproot only 15 to 37 cm (6 to 15 in) long and extremely fragile, which is why an established plant does not survive being moved. The heathland burns every few decades, and the dewy pine lives by it: individual plants persist only three or four years after a fire, and the population waits in the soil as seed until the next one.

Three things follow for the grower. The plant wants far drier conditions than any bog plant, and rots if treated like a sundew. It wants its roots undisturbed from the day the seed germinates. And it is short-lived by nature, to be raised from seed every few years rather than kept for decades.

The range in cultivation

There is one species and no named cultivars or forms, so the range in cultivation is a range of plant ages: seed, seedlings a few months old in small peat pots, or, less often, young plants already established in their final container. Seed is the usual purchase and the safest, because every later move risks the plant. Avoid buying a large plant that has recently been repotted.

Growing them

Light

Full sun for as much of the day as possible, outdoors or in a greenhouse with open vents. Indoors the plant needs the brightest window or a strong grow light; ordinary windowsills and terrariums rarely keep it for long, and plants do better outdoors than under glass.

Water

Use rain, distilled or reverse-osmosis water, and water the mix, not the leaves. Never stand the pot in a tray. In warm weather water every two or three days, otherwise once or twice a week, with the mix kept only slightly damp in winter and drier for some months after flowering. The principle is that the mix must never dry out completely, because a potted plant has no deep moisture to draw on and wilts fatally, yet it must stay much drier than any other carnivorous plant’s, because the stem and roots rot in a wet mix. A cool, moist winter does no harm. Where summers are wet, keep the pot under cover.

Growing medium

A mostly mineral, free-draining mix: equal parts pumice, perlite, sand and peat, or equal parts peat, lava rock, pumice, perlite and sand, so that peat makes up no more than about a fifth to a quarter of the whole. An unglazed terracotta pot is preferred because it breathes and dries, and it must be large from the start, 25 to 30 cm (10 to 12 in) across, because there will be no second pot.

Temperature

A warm-temperate plant. Summer heat is no problem if the mix is watered; cool, wet winters are what it is used to, and it takes light frosts. Plants survive brief dips to about -5 °C (23 °F) and summer highs above 38 °C (100 °F), but repeated freezes over weeks weaken or kill them; treat the lower figure as something a plant survives, not a target.

Humidity

The dewy pine wants moving air, not humidity. Rot follows warm, dim, stagnant, humid air, and seedlings are healthier outdoors, exposed to wind, rain and near-frost, than in a closed greenhouse.

Dormancy

None. Growth slows through winter and the plant keeps its leaves. Old leaves die and hang as a brown thatch along the stem; most growers leave them in place.

Feeding

Outdoors it catches flies, moths and other small insects in quantity, and it relies on them heavily. A plant under cover that catches nothing is fed small insects on the leaves. Nothing is added to the mix.

Common mistakes

The tray. Nearly every loss comes from treating the dewy pine as a bog plant: a saucer of water, a peaty mix, a humid propagator, and the stem rots at the base. The second mistake is the opposite, forgetting a pot in a hot spell until it dries right through, which wilts the plant beyond recovery. The third is repotting: an established plant cannot be shifted or divided, and a seedling is moved once, while tiny, in a peat pot that goes into the final container whole. The fourth is impatience with seed: untreated seed germinates slowly and in cool conditions, and a pot that has shown nothing after a month is kept, not emptied.

Which to start with

There is only one species, so the choice is how to begin. Sow seed in autumn where the pot can sit outdoors in cool air, at roughly 4 to 16 °C (40 to 60 °F); about two seeds in three come up, some of them months later. The seed germinates only in cool conditions, between about 15 and 20 °C (59 and 68 °F), and not at all in warm ones. Nicking the seed coat raises germination above ninety percent, and rubbing the seed between sandpaper sheets does the same job; gibberellic acid, which helps many other seeds, does nothing for this one. Sow in small peat pots so the seedling never has to be handled, and plant pot and all into the final container when the seedling is about 5 cm (2 in) tall. Someone who has never grown a carnivorous plant should start with a Cape sundew first.

Going further

There is nowhere further within the genus, but a grower who keeps a dewy pine alive for three years has learned the routine for the other dry-ground flypaper plants, the Australian rainbow plants of the genus Byblis and the South African Roridula. Seed is the only way to multiply it; the details are in Propagating Drosophyllum, and the guide to water and growing media explains why the mineral mix matters.