"For he shall grow up before him as a tender plant, and as a root out of a dry ground: he hath no form nor comeliness; and when we shall see him, there is no beauty that we should desire him."
The first "he" is a reference to the Messiah. The second "him" is either the Father in Heaven or Israel.
The Messiah will be a "tender plant" or a "root" that arises "out of a dry ground" because the barren, unproductive, rancorous people among whom He will be sent will not be producing redeemed souls when He comes. They will be racked with religious falsehoods; ambitious and controlling men who have obtained their leadership through political maneuvering, influence peddling and purchase.
The acquisition of religious status was so normal a thing in that day that the Apostles would later be asked by Simon if he could purchase the priesthood from them. (Acts 8: 13-24.) And yet the Messiah will find the way back to opening the heavens, receiving power from on high, and then go about preaching and leading other souls to redemption as well. For Him the barren, dry ground will be no impediment to salvation.
The Messiah will "have no form nor comeliness," and have "no beauty." Not because of His physical appearance, however. It will be due to the lack of position, absence of credentials, failure to hold a leadership position, and outsider status which makes Him undesirable. Those who recognize in His message the voice of the Lord will be required to overlook His obscurity and status. I've described this more fully in two chapters in Come, Let Us Adore Him.
This image contradicts the presumptions of the people who hear Isaiah's report. They imagine themselves as followers of the true faith. They presume they would hearken to the voice of God no matter when it came. But they look for it in barren ground. Therefore, when the Messiah should come, they will be unable to find anything desirable, beautiful or comely about Him. Rather they will shout "crucify Him!" because He will have merited the charge of blasphemy.
For those who heard Isaiah's report, this would seem altogether wrong. It is incomprehensible for the chosen people to fail to recognize the Lord's own Son. And yet they will kill Isaiah, as well. So when the message of the prophet Isaiah came to pass, the generation in which it was fulfilled was entirely oblivious to how his prophecy was unfolding before their eyes.
This is the Lord's doing, and it is marvelous in our eyes.