Dodder – A Parasitic Plant

The Cuscuta genus is the only parasitic genus in the Convolvulaceae, otherwise known as the bindweed or morning glory, family of plants. And Cuscuta species, commonly known as dodders, are the most well-known and widely spread example of stem holoparasitic plants. That’s right, these plants are obligate parasites. They do not contain chlorophyll and cannot, therefore, photosynthesize to make their own food. They must acquire the needed nutrients and water from their host plants.

Folk names, in English, for plants in this genus include wizard’s net, devil’s ringlet, strangleweed, and witch’s hair, to name just a few. I love the imagery of these terms! And once you’ve seen this plant in action, you realize these are great descriptions of these plants that climb, scramble over, and entwine themselves on their host plants with their slender, thread-like stems.

And it is from these many stems that grow haustoria, specialized tube-like growths that insert themselves into the vascular system of the host plants. This allows the dodder to absorb nutrients and water, and therefore grow and attach itself to multiple plants.

Because the plant does not photosynthesize, there is not much need for leaves, and so the leaves on dodder are very tiny scales. The stems range in color from reddish to yellowish. The small flowers are white, yellow, or cream colored and always hermaphrodites. The stems coil in a counter-clockwise direction.

The parasitic dodder seedlings can germinate and sprout but need to find a host plant quickly, usually within 5 – 10 days, or they will die. They have therefore adapted to use chemosensory, or an ability to sense chemical signals, to grow towards nearby plants. Until they are able to reach a host plant to parasitize, they rely on the food stored in the seed.

Dodder is parasitic on dwarf shrubs, herbs, and grasses and prefers soil with low salinity. We came across dodder in the small oasis of Um Saida (pictured below), near Wadi Kid. The dodder was growing across shrubs of Fagonia sp. as well as herbs such as wild mustard, or jahag (Diplotaxis acris). The dodder was tangled and growing over many plants, clearly illustrating how this could become a problem if the plants parasitize agricultural crops.

There are three species of dodder found in Sinai: Cuscuta palaestina (Palestinian Dodder), C. planiflora (Flat-flowered or Small-Seeded Alfafa Dodder), and C. campestris (Field Dodder). Although Cuscuta species have a rich history of traditional uses in folk medicine around the world, I came across no recorded uses in Sinai in any of the research I was able to access. I am curious to speak with more Bedouin who are familiar with the dodder growing in Sinai.

Desert Thumb

Desert Thumb (Cynomorium coccineum), aka Red Thumb or Tarthuth in Arabic, is not a common plant in Sinai. Growing in the spring only after a wet winter, this rare plant makes for a special spotting! I was intrigued when I came across these for the first time in 2014. I mistakenly thought they were mushrooms (so did the Maltese back in the 1600s so I’m not the only one!). With the help of my fellow nature lovers at Project Noah, I learned that these thumbs of the desert were actually plants.

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But they are no ordinary plants! They are parasitic; they have no chlorophyll and cannot photosynthesize. Instead, they live most of their lives underground as a rhizome, attached to the roots of another plant. In Sinai, Desert Thumbs most likely parasitize salt bushes (Atriplex spp.), but they are also known to live off the roots of Amaranthus and Tamarix species.

The stalk emerges in the spring, covered by clusters of tiny dark red to purplish flowers. The flowers are pollinated by flies that are attracted to their cabbage-like aroma. Once pollinated and mature, the spike turns black and produces small, black, nut-like fruit.

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Desert Thumbs are edible and are believed, throughout the region where they grow, to have an array of medicinal properties. In fact, Arab physicians during the Middle Ages referred to Desert Thumbs as “the treasure of drugs” because it was used to treat a range of problems from blood disorders to digestive and reproductive ailments. In Sinai, Bedouin have traditionally used these plants to cure colic.

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Bedouin in Saudi Arabia have been harvesting tarthuth for thousands of years as food for themselves and their camels. Tarthuth has been especially useful during long caravan treks through the desert as well as during times of famine. The spikes are cleaned and the outer skin is peeled off. The inner white flesh is reported to be like an apple – sweet, crisp, and juicy.

If I had known that three years ago, I definitely would have tasted this plant! We’ve had a relatively wet winter this year, so maybe I’ll get lucky and have another chance to sample a Desert Thumb this spring. I’ll be sure to let you know. 🙂

References and Further Reading:

Cynomorioum – Wikipedia

Cynomorium coccineum – Flora of Qatar

The Matelse Mushroom (Cynomorium coccineum): An Epic History of the Rise and Fall of the Treasure of Drugs

The Treasure of Tarthuth by Robert W. Lebling Jr. – Saudi Aramco World