Dodder is the name given to species of the genus of climbing parasitic plants Cuscuta which have their leaves reduced to tiny scales and loose their roots soon after finding a suitable host. They belong to the morning-glory or bindweed family, Convolvulaceae, although they are sometimes placed in their own family, Cuscutaceae.

Dodder is a total plant parasite which has no chlorophyl and relies wholly on its host for all its nutritional needs including water, organic substances and minerals. The commonest of the British species of Cuscuta grow on clover, gorse, heather, hops, nettles, and many other plants. The fine stems of dodder give its host the appearance of being covered in fine pink cotton thread.

The seed of dodder contains a thread-like embryo and germinates pushing a small root into the soil to gather water while the thin pink stem spirals upwards (nutates) rapidly in everwidening circles searching for a host plant. If a host is not found in time, the dodder will die through lack of nutrients. If the stem does come into contact with a host, it twines around it and sends adventitious roots known as suckers or haustoria which penetrate the host's tissues to connect the dodder's phleom and xylem with that of its host and thus the dooder draws the water and nutrition it requires - it's own temporary root dies.

The stems of dodder are reddish and the leaves have become reduced to minute scales. Its tiny flowers grow in round clusters. The parasite branches and grows so vigorously that it may kill the host plant, partly through shading, but mainly through exhausting it of organic metabolites.