One of the most destructive weeds that crop farmers must deal with is the Canadian thistle. It has an extensive root system that makes it extremely difficult to eradicate once it is established. The root structure can reach a depth of fifteen feet, and the roots can also spread out the same distance horizontally. These prolific roots crowd out the plants. Just twenty thistles in one square mile of field can reduce barley yield by a third or alfalfa yield by one half! Canadian thistle is also very damaging to feed crops, as livestock will not graze near it.
In the parable of the sower and the seeds, Jesus described people who are not fruitful because the Word of God that is planted in their heart is choked out by thorns. He gave us specific thorns we must guard against such as the cares of the world; when we succumb to this particular thorn, anxiety and fear can fill our hearts and minds. We live in an uncertain world, and unless we maintain our faith, it will be easy for anxious care to choke out the Word.