Which seed did Jesus say was the smallest seed planted in the ground?

Jesus said the mustard seed was the smallest seed planted in the ground. He used it in a parable about the kingdom of God, recorded in Mark 4:30–32 and Matthew 13:31–32.

The image emphasizes dramatic growth from a tiny beginning. In the parable, the seed grows into a large garden plant with broad branches where birds can nest or find shade. Luke 13:18–19 also preserves a closely related version of the teaching.

The statement is not generally treated as a modern botanical claim that mustard seeds are literally the smallest seeds in the world. Mustard plants common to the biblical setting—often associated with black mustard—were familiar agricultural plants whose small seeds could grow into substantial shrubs. Some translations clarify the comparison as the smallest of the seeds people planted or cultivated.

A common mix-up is confusing this parable with Jesus’ teaching about faith “like a mustard seed” in Matthew 17:20 and Luke 17:6. Those passages also use the mustard seed as a symbol of great results from something apparently tiny, but the question about a seed planted in the ground refers specifically to the parable in Mark and Matthew.