Instead of enthusiasm, they just waved. Come on, how do you think that if the seed emerges, you will live till it becomes a huge tree? It takes very long time and anything can happen to you and the tree. You can move out from here and the tree can be cut before it grows a huge canopy. The boy was desperate and complained to his mother about what he had heard. How did you think, Mom, that I would be alive until it becomes a big tree? Do you want me to be fooled? No, said the mother. Listen, my son. The point is not what we get finally from the seed. The point is to give love and care. As long as we are able to do so, the seed will release its creative power and will evolve. We don't know what it will be like and how long we can see the little seedling, the branches, the foliage. We are not curious about the end result, but the process. It gives us feedback that it was worth investing our love and care.
We do not know what our children and disciples will become. What will be formed out of the seeds we have sown? The result doesn't matter what will be. What matters is that we started to bring them up with loving care. The one is a fool who wants to see the end of the road at the beginning of the road. Meanwhile, the goal is not to arrive, but to be on the road and enjoy every part of it. We cannot accompany every life, but we can witness, actively participate, and shape many stages of lives of people. These are the sections of the road that we walk together with others and we never know how long the common road will take, where will we turn to different directions.
What keeps together the tree and the little boy who planted the seed? Common experiences, love, care, need for one another, and life stages in development, growth, and fulfillment. The feeling that it was worth to spend every day with each other. This is what bonds people together, too. If this feeling does not develop, then the relationship is worthless to continue.
The symbolism of tree is present many times in spiritual messages.
The tree of immortality, the tree of knowledge, the tree of Zaqqum or the one of which feeds from good or bad. There are many numbers of messages while real trees surround us. All we notice is that we cut them out and put fire from them. We use them only for the purpose and do not notice the message. Life is poor if it is only utilitarian.

Seest thou not how Allah sets forth a parable? - A goodly word like a goodly tree, whose root is firmly fixed, and its branches (reach) to the heavens,- of its Lord. So Allah sets forth parables for men, in order that they may receive admonition. (Quran 14:24)

"Goodly word" is usually interpreted as the Divine Word, the Divine Message, the True Religion. It may also be interpreted in a more general sense as a word of truth, a word of goodness or kindness, which follows from a true appreciation of Religion. For Religion includes our duty to Allah and our duty to man. The "evil word" is opposite to this: false religion, blasphemy, false speech, or preaching or teaching unkindness and wrong-doing.

It brings forth its fruit at all times, by the leave of its Lord. So Allah sets forth parables for men, in order that they may receive admonition. (Quran 14:25)

And the parable of an evil Word is that of an evil tree: It is torn up by the root from the surface of the earth: it has no stability. (Quran 14:26)

And here it is! We have come to the figurative sense, where the good word is the seed from which a blessed tree sprouts out and the bad word is the opposite. Staying with our original parable, we may not live till the mature state of the tree, so we may not live till we see the fate of the doctrine which develops from the good word. We can do one thing. We can nurture the word with loving care, from which the thought springs out and pass the thought forward with loving care while it is flourishing, bringing many seeds that fall into fertile soil. Do not desire to live till the end, but give thanks to Allah for to live at beginning of a journey and to walk on a section of the road where you can take care of the life of a seed, sprout, seedling or tree.