25th July, 2004  Volume 11, Issue 2

















A thorny affair

By Risidra Mendis


Ornamental plants such as cactus, euphobias, bougainvilleas, bromeliads and       crypthanthus     known for         their thorns are a common sight in many gardens these days. But despite the popularity of these plants, bought especially for their pretty flowers, some plant sellers are openly telling their customers that cactus thorns can be cancerous if retained in the human body.

According to these plant sellers, the cactus and bougainvillea thorns are known to be more poisonous than the thorns of other plants. However there are mixed reactions among plant growers and sellers these days with regard to this thorny issue as there is no scientifically proven data so far to say that thorny plants can cause ailments and other types of diseases.

Former President Dehiwela, Mount Lavinia Horticultural Society, Sunila Rajawasan, was pricked by a cactus thorn when she was 14 years old. "I was playing with my friends and ran to catch the ball that went towards a big cactus tree. I scraped my hand on the thorns of the cactus" recalls Rajawasan.

According to Rajawasan she didn't pay much attention to the wound and soon had forgotten about it. Three weeks later, Rajawasan couldn't walk and talk, and had to be taken to a doctor. "The doctor asked me if I had any wounds and when I told him about the cactus thorn he told me I was suffering from the last stages of tetanus. I was immediately hospitalised and treated," says Rajawasan who had a narrow escape from death.

Dangerous inside

Rajawasan went on to say that thorns from bougainvilleas, citrus plants and cactus could be dangerous if the thorns remain inside the body. "The best thing to do is to remove the thorn immediately" explained Rajawasan who also said that the thorns from big cactus trees can be more dangerous as opposed to ones from small trees.

This is one of the reasons why a lot of research on plants is carried out in foreign countries and plants are propagated in foreign countries with fewer thorns and in some instances even without thorns.

Meanwhile, Gemunu Wijesinghe who specialises in growing bromeliads said there was no reason for people to worry about the thorns. "I have been pricked by the bromeliad thorns many times while transplanting and handling them" explained Wijesinghe.

"Bromeliads are easy to grow and can adapt to most climates. However these plants don't adapt to very cool climates" explained Wijesinghe. According to Wijesinghe, bromeliads prefer rain water to pipe-borne water.

According to Wijesinghe, a well known German expert on bromeliads who has conducted many research programmes on these plants has said, the thorns of the bromeliad have no connection with cancer or any other disease. "Bromeliads unlike many other flowering plants retain their flowers from a minimum of two weeks to eight to 10 months" says Wijesinghe.

Thorny varieties

Another plant seller who sells plants at plant shows said he has been growing bromeliads, crypthanthus and euphobias for the past 20 to 25 years. "I have got scraped and pricked while growing these plants. My arms have bled from the wounds due to the thorns of the bromeliads quite often, but I have never had a serious problem" added the plant seller.

Bromeliads are an imported variety of plants and come in a variety of bright coloured combinations. "Bromeliads generally grow well if they are exposed to 50% sun and 50% shade and are ideal to be grown on high surfaces so that the attractive colours on their leaves are visible" says Rajawasan.

According to Wijesinghe, the crypthanthus is another type of thorny plant that belongs to the bromeliad family. "This plant that also comes in a variety of colours is easy to grow and is not harmful to people" added Wijesinghe.

Meanwhile Rajawasan went on to say that the thorns on euphobias, a popular plant in many households are not harmful as opposed to other types of plants. However the milky substance of the plant could be poisonous to humans," explained Rajawasan.

The ideal conditions to grow euphobias are 50% sun and 50% shade. "People should take care when growing bougainvilleas known for their thorns. If you have bougainvilleas in your garden and get pricked by a thorn you must remove the thorn immediately," says Rajawasan.

Defence mechanisms

Speaking to the Sunday Leader, Director National Botanical Gardens, Peradeniya, Dr. D.S.A. Wijesundara said most plants, including many food plants in the raw stage have lots of defensive chemicals in them.

According to Wijesundera plants' defence mechanisms can be divided into thorns and other physical means to keep grazing animals away, chemicals that cause skin irritation in come cases and toxins that cause illness or death if consumed.

"Thorns damage skin and can even facilitate microbial infections - for example, tetanus.

If a human has an open wound this is a way for bacteria to get in, and increases the risk of tetanus. A puncture with a thorn can push bacteria into the body where the body is  not ready for it. The most obvious category of plants that can cause puncture wounds is cacti," explained Wijesundera.

According to Wijesundera, a helpful hint to get cacti thorns out of the skin if you are unfortunate enough to brush against it, is to place sticky tape or sellotape on your skin and then pull it off, hopefully taking the glochids with them.

Wijesundera went on to say that in some plants it is the latex that is dangerous. "Phorbol esters are found in the latex of euphorbia species and research done in Germany and elsewhere has shown that E. millii has those co-carcinogenic esters. Our local medicinal plant Euphorbia  tirucalli  (nava handi) also has these esters. However one must not blow these out of proportion as we are living in a world full of carcinogens, co-carcinogens (cancer promoters), other harmful substances and occupational dangers" explained Wijesundera. 

Dr. Balawardena says...

Speaking to the Sunday Leader, Consultant Oncologist, Cancer Hospital Maharagama, Dr Jayantha Balawardena said as far as he knows there is no scientific proof that any thorny plants are cancerous. "There are many stories that say passion fruit and kathurumurunga leaves are cancer causing food. This is not true. In the same way plants cannot cause cancer in a person" explained Dr Balawardena.

According to Dr Balawardena any long lasting wound inflicted due to whatever reason in the body, could be a cause for marjolin's cancer. A patient may have diabetes and the wound may not heal. This longstanding wound could be a cause of cancer," says Dr. Balawardena.

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