Luke 21:29

“And he spoke to them a parable, “Behold the fig tree, and all the trees, when they now shoot forth, you see it and know of your own selves that the summer is now near.”

The parable is a simple one, and its basis is that men know when summer is coming because they observe the growth on the trees. Luke's addition of ‘all the trees' (contrast Mark 13:28) makes clear that nothing is to be gathered from the description of a particular tree. The fig tree is mentioned as the early blossomer, but the principle applies to all the trees. So the principle in his view is a universal one, and we need not doubt that he gathered that from his source. That being so the parable signifies nothing more than that His people should be observant and recognise that growth on trees reveals the approach of summer. But it is an indicator, not a guarantee. The summer is seen as ‘near', not ‘now here'. In context the distinction is important. For in eschatological terms ‘near' is subject to the timing of God with Whom a thousand years is as a watch in the night. As always the signs are in order to awaken interest, not in order to indicate certain timing. Jesus always rejected the idea of giving signs which would replace faith. They could be used to bolster faith, but not to replace it.