Despite the value of mustard seeds for flavor and medicinal purposes, it is not something you want in your garden. Think mint on steroids. It does grow into a fairly large bush, maybe four feet tall, and will spread quickly to every horizon. And what would you do with all that mustard plant? If you have ever cooked mustard greens, you will know that a little bit goes a long way. It has a horseradish kick, and you are not going to eat like you would potatoes or tomatoes. Mustard, in the Middle East, is a weed growing on the hillside, filling in the untamed and agriculturally undesirable spots. )
John Dominic Crossan, commenting on the parable of the mustard seed, observes that “The point is not just that the mustard plant starts as a proverbially small seed and grows into a shrub of three, four, or five feet in height. It is that it tends to take over where it is not wanted, that it tends to get out of control, and that it tends to attract birds within cultivated areas, where they are not particularly desired. And that, said Jesus, is what the Kingdom of God was like. Like a pungent shrub with dangerous take-over properties.” (Jesus A Revolutionary Biography, page 65).