A "triffid" is a fictional plant first featured in a 1951 novel by John Wyndham. I haven't read the book, but I saw the awful 1962 movie based on the book. I've also listened to a BBC radio drama that was better in my opinion. In the movie the triffids are tall plants that start showing up in large numbers. They can walk around slowly and they eat people. They tend to hang around until someone passes by and they either ambush the person or start chasing him or her in large numbers.
Several years back I noticed a few plants that showed up in one or two parts of the pasture. They were small and seemed harmless. After a few years I started seeing them everywhere and I realized I had a problem. They turned out to be a type of mustard. Every time I see one I'm reminded of triffids. I strongly suspect them to be shortpod mustard (Hirschfeldia incana) which is bad because they can live for more than one year. They start out in the spring as a basel rosette but then send up a rapidly growing flowering stem. This can grow several feet and send out multiple branches. The stems become wiry and covered with tiny seed pods that can have sharp tips almost like spines. The stems dry up by mid summer leaving behind a spikey tangle of stems ready to shed seeds everywhere. They can be tricky to spot and can range in size from a single stem only 6 inches tall to a monstrous branching thing several feet wide and tall. The bison will eat the young leaves but don't touch the wiry stems.
The time to search and destroy them is now and I've been pulling up as many as I can find every spring for the past two years. Each year I pull up several huge piles that I allow to dry in the Sun and then burn. So far I haven't seen a reduction in their numbers but I'll keep it up. Last year I read that the leaves are edible and found them to be a good addition to put in salads or on top of burgers. They are very strong. Almost like horseradish.