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The Vampire Orobanche

A look back on the dark story of a prairie parasite for the stormy days.

The Vampire Orobanche uniflora below the ruins of a bracken fern

It was a dark and stormy prairie. The oscillating early spring was in turmoil with much emergence, with newly burning sun streaks and the biting chill and rain. And there is something underground. It lurks silently, unseen, unheard, but always there, if you know where to look and if you dare. From coast to coast of states united, and southern border to beyond the northern, across our whole nation and more, it hides unseen by most, waiting. It has been known by many names, including “the plant that should not be named”. In this day its name insights unease. What is in a name? An identity? A hint of history? Some names are misleading anyway, like "ball moss", which is not even at all a moss. But that is another eerie tale.

Colony of naked broomrape among a Lomatium utriculatum

There are hundreds of this creature's kind scattered all over and yet seldom encountered, and each a different flavor of wicked. Some have always been among us, feeding on the locals slowly and gently. Some are new-comers to these shores, wreaking havoc upon our crops, draining their sustenance before they reach our own lips. One particular beast stalks our Northwestern lowlands, only seen by the patient eye that looks very low, very close to their resting bed. It is the Orobanche uniflora, the “one flower” (uni-flora) because he erupts singular smoky purple pipe-like flowers while all other Orobanches sprout clusters like multi-eyed beasts of the fairy realm. Their names are spoken in hushed tones and hurried whispers; Orobanchaceae, the broomrapes. Whether naked, spiked, or one flowered, Orobanche species’ dark secret is encompassed at the very name, for “orobos” in Greek refers to plants of the vetch group and “anchein” means “to strangle”. Hence it is the plant that strangles vetches. And yet not where we can see this crime of plants. These are underground stranglers.

an underground unseen slow-motion tussle

From Latin, the broomrape once had a much different meaning than it conjures today. “Rapum” was the name for tuber-bearing plants like turnip, or any such plant akin to the sharp and bitter mustards. You now know what seeds we steal rapeseed oil from then. Brooms are another name given to vetch plants that are often seen growing alongside their strangling namesake. So the broomrapes were thought as a sort of tuber of these vetchs (the rapum/mustard of the broom/vetch), and possibly strangling mustards. Even their name is twisted, you see? The olden time naming ones, scribbling titles in the ancient books branded these small unassuming plants with names that would then mutate and darken in modern days. Yet the namers didn’t know this Orobanchaceae family’s subsurface secret. But when they learned to call them cancer roots, that is when the shade became lifted from their widening eyes. For the broomrapes, the cancer roots, the Orobanche, are pure parasites. The “cancer” refers to the ominous knobs they emerge from like free floating tumors in the soil, growing a feeding hungry parasite.

Close-up for scale of about 2” tall Orobanche uniflora, clearly lacking leaves

Where the small and unassuming Orobanch uniflora grow, no daisy, legume, or sedum is safe whether in a damp wood or open exposed field, even in your own cut lawn. Unlike the better known facsimile of the Indian pipe, similar only above the dark soil surface, Orobanche is a vampire. A plant vampire. Indian pipes, in contrast, are an eerie looking yet harmless type of saprophyte, merely eating the dead remains of others and releasing what nutrients are locked within death’s cold embrace. But Orobanche is a true vampire, a full obligate parasite feeding upon others as they live and breathe and grow, though growing slower now with the earthly bite of Orobanche soft and stubbornly lain upon their roots.

Young newly emerged flowers

Deep below the soil where the damp holds for ages, the fleshy somewhat tubular cancerous mass sends out a searching tendril that clasps at unsuspecting new hosts. Mature enough hosts unknowingly release a biochemical lure that triggers the minute long-waiting Orobanche seeds to erupt from their hindering shells, having initially been scattered far by the whipping prairie winds. They grow first as little more than transparent wisps that will perish if further than a mere 3 mm from a needed host root. Proximity to their victim is key. Once this specialized root haustorium makes its predatory bond (think of them as a vampiric tongue) there is no hope for the unwilling host' freedom. They strangle a hold upon the victim’s root flesh in an underground unseen slow-motion tussle as their haustoria penetrate and seal connections over the goldenrod, sedum, or saxifrage root. Then they draw at will upon the vasculature, the life blood, of the victim, keeping it alive to feast on for years.

Orobache needs to feed

Orobanche long ago gave up on producing its own food, not bothering to make chlorophyll with its leaves mutated and shrunken to little more than reptilian scales. It is a relative of the often hemi-parasitic and fellow haustoria-producing family of Scrophulaceae like paintbrushes (see golden paintbrush below), though they look almost entirely different at first glance, and hemi-parasites could spend a full lifetime without feeding on others. But Orobache needs to feed from the very start to their last days. Their first root or radicle sniffs out the biochemical exuded from their victim like a blood hound tracks a scent, and must be close to quickly start its feeding before it runs out of its small seed-store of nutrients.

Castilleja levisecta, golden paintbrush, distant relative to broomrapes
Close up of Castilleja (paintbrush) flower showing the tubular galea of fused petals & two-lipped, similar to Orobanches

Once locked upon a root to suck from, the vampire Orobanche quickly engorges the upper portion into a nodule, swelling like a tuber (or 'rapum', remember?). Then it sprouts new reaching tendrils that lurch towards more host roots, attaching in new places, and locking a firmer and firmer hold, ever feeding and draining. Yet a mature enough host may barely show a strain, like the tiny vampire bat lapping an insignificant amount of blood from a full size cow. Soon the mass swells higher into a shoot, looking more like the docile photosynthesizing plants we well know.

The next flowers emerging below a fully open Orobanche pipe

After several weeks of feeding and swelling and distending, briefly they erupt above the crumbling soil purely to reproduce and spread their seed. And the search for more victims begins anew. They lay in wait for years, quietly and patiently sniffing for their next prey to happen near. Careful where you step my dears. If fear grips you as an exotic noxious Orobanchacea species feeds too much upon your tender crops, a few species of alluring biochemical-producing plants may trick the pest into germinating its seeds but not be able to connect and sap life from their roots. These plants include bell peppers and coat buttons (Tridax procumbens) and thus can server somewhat like garlic to the bloodsucking human undead, reducing a noxious Orobanche infestation.

The native vampire Orobanche uniflora is still beautiful and a beguiling uncommon wicked little gem. Be glad they don’t feed on us, and dare to take a peek into the small throat of the singular naked and hairy purple pipe flowers. If you dare put your face so close. I’m pretty sure they don’t bite, but best to not poke even a little bear, don’t you think? A rose by any name still has thorns after all. And this do have roots that are HUNGRY.

The shallow throat shows the pollen laden stamen within

References & additional reading including a similar page on their haustorium connections and semblance to vampires.

Gracie, Carol. April 2020. Spring Wildflowers of the Northeast: A Natural History. Princeton University Press, pg. 146-148

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