Luke 13:19

“It is like to a grain of mustard seed, which a man took, and cast into his own garden, and it grew, and became a tree, and the birds of the heaven lodged in its branches.”

Jesus then pointed out that it was like a grain of mustard seed, the smallest seed known to the farmers of Palestine. Yet when a man sowed this tiny seed it grew until it became a large bush, sometimes even up to twelve feet (four metres) high, so large that the birds, who loved the small black mustard seeds, could come and lodge in its branches (compare especially Ezekiel 17:22, where a sprig planted in Israel will grow until it is a blessing to all the world so that the birds nest in its branches; and Daniel 4:21 where the birds represented captive nations). Of all the herbs it was a phenomenon. No other herb grew like it. Thus the Kingly Rule of God would grow from small beginnings (Luke 12:32) by the spreading of the word, becoming larger and larger, and would reach out even to other than Jews as ‘the birds of the air' gathered on its branches to partake of its blessings.

‘Garden.' In Matthew 13:31, in a different context, the mustard seed was sown in ‘the field', i.e. the countryside. That the latter did happen is supported in Rabbinic sources. This would suggest that in Palestine there were different agricultural approaches towards the growing of mustard ‘trees' from seeds, which is quite likely, for they were herbs. They could thus be grown in the countryside, or in gardens. There is thus no need to require a Gentile environment because of the use of ‘garden', although it is always possible that Luke is translating in accordance with the general custom of his readers in growing mustard bushes.