Easily mis-identified as : Dodder (Cuscuta epithymum) which also has red stems, is a bit less rare ([R]) than Greater Dodder's [RR] rating, always has 5 petals (unlike the 4-5 of Greater Dodder). To differentiate between the 3 species of Dodder the length of the styles in comparison to the height of the ovary must be carefully observed, as well as the presence or absence of a small round stigma. This means having opened flowers to tell.
Almost uniquely identifiable characteristics
Distinguishing Feature : Instantly recognisable as one of the Dodders, but which one...
Greater Dodder feeds parasitically primarily on Stinging Nettle (Urtica dioica). It likes to be near water, is decreasing in occurrence and is found locally in England south of Peterborough. It is not common and really quite rare.
Although your Author has given it a heading of a 'climber' (on account of the coiled spirals that wrap and tighten their grip on host plants) it does not seem to be able to climb by means of the tendrils, although it can hang from the branches of trees and shrubs by this means.
Unable to synthesize chlorophyll, Dodder is a hemi-parasitic plant which is parasitic on other plants an depends upon them for all its nutrients. It sprawls all over suitable plants, tapping into their resources via haustoria which insert themselves into the host plants. It twines anti-clockwise around the host plant, tightening the loose coils as it does so which initiates the growth of the haustoria on the coils to tap into the plant. The host plant is usually Gorse, but
Heather and Wild Thyme are also likely hosts. After tapping into the host, the plant continues to grow loose spirals until they too find a host and the coils tighten again to gain nutrient contact. Dodder plants do initially possess their own roots, but they soon die off once they have tapped into the food supply of a host plant. If, however, the Dodder fails to find a suitable host within 2 to 5 days of germinating from seed, then the Dodder will die. Once it is successfully attached to a host plant it will grow and spread to cover other distant plants, possibly tapping into those too. Although an annual itself, if it taps into a perennial galls can form at the attachment areas over the winter, and when spring arrives new Dodder plants can develop from these galls.
Dodder detects the presence of certain desirable host plants by the volatile organic compounds that the host produces, and is able to home in on the host plant, wrap its tendrils around it and tap into it if it deems the host beneficial. But the host plants are not defenceless in this attack, and often synthesize deterrent and toxic molecules (phytoalexins) in response. Dodder does possess leaves, but they are minute and scale-like, and, lacking chlorophyll, not green. Dodder is thus
holoparasitic, unable to photosynthesize it must parasitize to obtain all its needs.
There are several other Dodders, one,
Greater Dodder (Cuscuta europaea) ([RR]) is rarer than Dodder ([R]) and prefers Stinging Nettle (Urtica dioica) (but unlike Dodder is able to parasitize almost any other plant within reach) but Yellow Dodder (Cuscuta campestris) is apparently not rare but rather a non-native garden escapee which prefers to parasitize
Somewhat surprisingly, some parasitic plants are able to parasitize themselves, a phenomenon called self-parasitization. Species of Dodder are one such, Mistletoe too in some instances.
There are reports that Dodder smells foul (reminiscent of rotting fish) when it is flowering and those flowers are ripe for pollination. At other times there is no detectable odour. One of it's colloquial synonyms is 'Devil's Guts', which explains a lot. Rotten fish smells of amines, so Dodder must emanate amines during those periods. It seems that the plant uses the rotting smell to attract blow flies which will then pollinate the plant. One of those amines could well be either Putrescine or Cadaverine or even both together.