A: Matthew is summarizing the meaning of Jesus statement for a readership which had never seen epiphytic orchids, and which saw casual axioms as what they were. Mark 4:31 preserves a form of Jesus statement which is closer to its verbatim form: a mustard grain which, when it sown on the ground, is the smallest of all the seeds upon the earth.
If Jesus had said something like, Except for epiphytic orchids, it would have been more distractive than instructive to His listeners, and so He described the mustard seed in simple general terms which anyone in an agrarian society like the society of Galilee and Judea could and would understand.
Orchid-seeds may not have even been considered seeds in the first-century method of classification; seeds were tithe-able and thus countable; orchid-seeds would not be countable in those days due to their extremely small size. Also, as far as I know, orchids were not a domesticated plant in first-century Palestine. So, objecting to Jesus' statement about the mustard seed is something like objecting to someone who gave the answer "Mount Everest" to the question, "What's the tallest mountain?". One /could/ say that the correct answer is really Mons Olympus on Mars, but while that is technically correct, it's also meaningless to audiences whose members have no knowledge of the existence of Mons Olympus. Would the same people who have objected to Jesus' reference to the "least of all seeds" also object if a teacher, in the course of drawing an analogy, referred to Mount Everest as "the tallest of mountains"? I doubt it. ( ... well, /now/ they might... )
But if modern readers insist on magnifying a casual axiom into something it was not intended to be, and interpret Jesus' words as a description of all seeds, whether of domesticated grains and herbs in Palestine or of flowers in Central America -- there's still a simple resolution to the objection. The seeds of epiphytic orchids, by definition, are not sown upon the earth (as the website to which the SAB links to at this point says, Epiphytic plants are non-parasitic plants that grow on other plants) and thus are not part of the comparison that Jesus was making.
Second Q: There are no trees in the mustard family. Mustard-seeds do not grow into trees large enough to support bird-nests. So isnt Jesus wrong to call a mustard-plant a tree?
A: First, its simply not fair to project the modern classification of trees which excludes large herbs and bushes beckwards upon the classification-schemes (or lack thereof) in the first century. Some mustard-plants (probably Sinapis Nigra is the one meant here) in the Holy Land, though technically herbs, are capable of growing to considerable size -- over seven feet high -- comparable to the stature of some small trees. Second, this objection evaporates when one realizes that whats really going on here in Matthew 13:32 is that Jesus is importing imagery from Ezekiel 17:22-24.
Lets turn there: Thus says the Lord GOD: I myself will take a sprig from the lofty top of the cedar and will set it out. I will break off from the topmost of its young twigs a tender one, and I myself will plant it on a high and lofty mountain. On the mountain height of Israel will I plant it, that it may bear branches and produce fruit and become a noble cedar. And under it will dwell every kind of bird,; in the shade of its branches birds of every sort will nest.
Now, this cross-reference might suggest to some skeptical minds the shape of some new objection -- /Every/ kind of bird, eh? Even penguins and ostriches? -- but to me it shows that, while the mustard-plant in the parable does not behave like a typical mustard-plant, /That Is The Point/: it grows surprisingly into something bigger than any mustard-plant naturally has a right to be. Jesus is comparing the kingdom of heaven to a grain of mustard, and here has adopted Old Testament imagery (the birds-in-branches phrase occurs elsewhere) which figuratively described kingdoms which had grown from small beginnings.
(In other news: is this not what we have seen be unfolded in the history of the church? From a small group of 11 amateur evangelists and a few others, this Christendom has emerged which offers its fruit and its shade to many around the world. This parable is somewhat prophetic, and I think there can be no doubt that its predictive nuance is accurate.)
Yours in Christ,
Waterrock
[I edited this and expanded the third and fourth paragraphs while I was salvaging a garbled sentence.]


