Bright orange patches dot the green swath of a salt marsh. Look close and you will see what looks like a mat of fishing line or straw. Hundreds–thousands–of narrow orange threads are wrapped tightly around bright green pickleweed stems. Copious white flowers often bloom off the threads. This is saltmarsh dodder (Cuscuta salina), a parasitic native plant that mooches nutrients off its host plant. Instead of photosynthesizing its own food, it sinks tiny root-like organs (called haustoria) into the flesh of the plant. Once it taps into the vascular system it can suck out all the water, minerals and carbohydrates that it needs.
Dodder seeds are scattered by wind, tides and animals so there is no guarantee that they will germinate near a suitable host plant. But they die if they can’t find one quickly. It sounds impossible for a brainless, eyeless, noseless plant to do, right? Nope–not if a host is anywhere close. They can detect the volatile compounds emitted by the host (basically, its smell) and then they grow towards it.
There are a lot of species of dodder in the US, and some of them are parasitic to some of our favorite crops like alfalfa, potatoes and petunias. Though the group is much maligned as a result, some ecologists make a case for the role that parasitic plants can play in the natural environment. Species like dodder or mistletoe don’t decimate their hosts’ population, but they do create patchiness. And in ecology, patchiness tends to lead to diversity, which is a good thing!