There is by no means full agreement about the precise identity of the plant in Jesus’ famous references to the mustard seed. Two types of mustard grow in the Holy Land and probably grew there in Bible times: Black Mustard Brassica nigra and White Mustard Sinapis alba. Both species were either cultivated or gathered in Bible times, probably more for the oil, which was used in medicine and cooking, than as a spice. Both types are cultivated today.
Mustard plants are related to some other well-known food plants, such as collards, broccoli, cauliflower, Brussels sprouts, rutabaga, and Chinese cabbage. They are planted and harvested each year. They grow to 2 meters (7 feet) in height and have branches like a tree. At the ends of the branches there are bright yellow flowers with four petals, like nearly all the members of the Brassicaceae family. The seeds are small among the seeds of garden plants, being about 2 millimeters (1/12 inch) in diameter, but they are not by any means the smallest of all seeds.
The point of the mustard seed parable of Jesus is that something small can produce something very large and complex, like the kingdom of God, or like the amazing deeds of a person with faith.
At least thirty kinds of mustard are known in the world, twenty-one of them in Europe. Others are found in Northeast Africa, India, Japan, and China. The quality in focus in all of the Gospel references is the smallness of the mustard seed compared to the large size of the resulting plant. The translator must keep that in mind, even if a relative of the mustard is found. If no effective equivalent is available, it will be necessary to transliterate “mustard” from a major language.


Source: Each According to its Kind: Plants and Trees in the Bible (UBS Helps for Translators)
See also mustard seed.






