In Matthew 13, Jesus says:
31 “... The kingdom of heaven is like a mustard seed that a man took and sowed in his field.
32 It’s the smallest of all the seeds, but when grown, it’s taller than the vegetables and becomes a tree, so that the birds of the sky come and nest in its branches.” (see also Mark 4:30-32)
But most critics usually ignore a very important principle of Bible interpretation, and that is: context, context, context.
Like all excellent communicators, Jesus always addressed His audience in ways that they would most readily relate to. He was not there to give a science lesson using knowledge available to readers in the 21st century because that was not His purpose. Rather, He was teaching members of an agricultural society in 1st century Israel, and in such a way that they would remember His words most easily.
That is why Jesus gave them an example that any of them would find in their vegetable gardens, since the mustard seed is, in fact, the smallest seed found in garden variety plants found in Israel. After all, it would not have done His followers very much good for Jesus to speak about orchids when His audience was composed not florists or garden hobbyists, but of farmers, fishermen and tradesmen.
Mishnah 3.2. Cucumbers and cucumber-melons do not constitute kil'ayim one with the other. R. Judah said they do constitute kil'ayim. Garden-lettuce and wild lettuce, or endives and wild endives, or leek and wild leek, or coriander and wild coriander, or mustard and Egyptian mustard, or the Egyptian and the bitter-apple, beans and beans in carob-shaped pods do not constitute kil'ayim one with the other.
And so we see that Jesus was not just correct about the mustard seed being the smallest of seeds allowed to His Jewish listeners, but that He was also a very skilled communicator, well aware of which examples were best to use for His audience.
Jesus is Lord!
Thanks to Dr. White for this little nugget of information.
The Problem Of The Mustard Seed by John A. Sproule
Episode of "The Dividing Line" with Dr. James White, June 11, 2014
Jewish Mishnah 3.2 regarding Kil'ayim (prohibitions)