Parasitic plants that use impatiens as hosts include the European dodder ("Cuscuta europaea"). The management of nettles preserves a colony of the parasitic greater dodder. Parasitic plants such as mistletoe and dodder are included in the study of phytopathology. Once the dodder finds its host, it wraps itself around the host plant's stem. The dodder can grow and attach itself to multiple plants. In one study, tomato plants were found to employ complex mechanisms to defend against dodder. After a dodder attaches itself to a plant, it wraps itself around it. The original root of the dodder in the soil then dies. The district straddles the River Dodder. Its major tributaries include the River Dodder, the River Poddle and the River Camac. Dodder Park is located in Rathgar. Bridges over the River Dodder from the River Liffey to the southwest. Two small rivers, the Dodder and the Dargle, overflowed their banks due to the rainfall. The arch can still be viewed from nearby Dodder Park Road. It is not "flashy" like the Dodder but builds up over a period.