God created trees to be fruit bearing. Some give seeds, and nuts. Some give juicy fruits. Some have leaves that are useful for healing, and herbal remedies. Some of the nuts and seeds are useful for oils.
A fruitful tree is life giving, good for food. A tree that is not fruitful is often cut down and burned for heat, energy. God used the symbols of fruit-bearing trees for righteous men.
In discussing the amazement of the surrounding nations at the parting of the Red Sea and the drowning of Pharaoh and his chariots and horsemen, there is a reference in Ex. 15:13-17 to the people as plants.
"13 Thou in thy mercy hast led forth the people which thou hast redeemed: thou hast guided them in thy strength unto thy holy habitation. 14 The people shall hear, and be afraid: sorrow shall take hold on the inhabitants of Palestina.
15 Then the dukes of Edom shall be amazed; the mighty men of Moab, trembling shall take hold upon them; all the inhabitants of Canaan shall melt away. 16 Fear and dread shall fall upon them; by the greatness of thine arm they shall be as still as a stone; till thy people pass over, O LORD, till the people pass over, which thou hast purchased.
17 Thou shalt bring them in, and plant them in the mountain of thine inheritance, in the place, O LORD, which thou hast made for thee to dwell in, in the Sanctuary, O LORD, which thy hands have established." (KJV)
Isaac's descendants were compared to plants being established in God's mountain, which mountain is another symbol for His sanctuary, or His kingdom. God's mountain is God's kingdom (Isa. 11:9; 56:7; 57:13; 65:25; 66:20; Ezek. 20:40; Dan. 9:16, etc.)
The first Psalm discussed a righteous man, a man blessed by walking in the way of the Lord, who meditates upon the law of God, and in verse 3 it compares him to a tree.
"And he shall be like a tree planted by the rivers of water, that bringeth forth his fruit in his season; his leaf also shall not wither; and whatsoever he doeth shall prosper." (KJV)
So, trees were often symbols for men. If they bore fruit, they were righteous before God. If they were unfruitful, they were ungodly, and of no use to Him, only good for burning.
"12 The righteous shall flourish like the palm tree: he shall grow like a cedar in Lebanon. 13 Those that be planted in the house of the LORD shall flourish in the courts of our God. 14 They shall still bring forth fruit in old age; they shall be fat and flourishing;" (KJV, Psa. 92)
Therefore, a righteous man (or woman) is a fertile tree, one bearing fruit for the Lord. A wicked man or woman is compared to grass that withers and quickly dies (Psa. 92:6-7)
In Isa. 61:1-4, speaking of his purpose as a prophet to the people, we find in verse 3,
"To appoint unto them that mourn in Zion, to give unto them beauty for ashes, the oil of joy for mourning, the garment of praise for the spirit of heaviness; that they might be called trees of righteousness, the planting of the LORD, that he might be glorified." (KJV)
"7 Blessed is the man that trusteth in the LORD, and whose hope the LORD is. 8 For he shall be as a tree planted by the waters, and that spreadeth out her roots by the river, and shall not see when heat cometh, but her leaf shall be green; and shall not be careful in the year of drought, neither shall cease from yielding fruit." (KJV, Jer. 17)
People who are righteous before God are trees of righteousness. But, unrighteous men are compared to brown and dead grasses, stubble and chaff before the wind (Job 21:18; Psa. 35:5; Hos. 13:3), chaff to be burned ( Isa. 5:24; Matt. 3:12; Luke 3:17), weeds and tares (Matt. 13:24-30) and brambles (Jud. 9:14-15).
Hos. 9:10 compared the people of Israel to a fig tree.
"10 I found Israel like grapes in the wilderness; I saw your fathers as the firstripe in the fig tree at her first time: but they went to Baalpeor, and separated themselves unto that shame; and their abominations were according as they loved." (KJV)
So, when the fig tree does not blossom (Hab. 3:17) then Israel does not blossom, or prosper.
As Christ was going into Jerusalem the second day after cleansing the temple, He stopped before the fig tree. Standing before Jerusalem, and standing before the fig tree - the same thing.
"18 Now in the morning as he returned into the city, he hungered. 19 And when he saw a fig tree in the way, he came to it, and found nothing thereon, but leaves only, and said unto it, Let no fruit grow on thee henceforward for ever. And presently the fig tree withered away. 20 And when the disciples saw it, they marvelled, saying, How soon is the fig tree withered away!
21 Jesus answered and said unto them, Verily I say unto you, If ye have faith, and doubt not, ye shall not only do this which is done to the fig tree, but also if ye shall say unto this mountain, Be thou removed, and be thou cast into the sea; it shall be done." (KJV)
The fig tree (Israel) was unfruitful and was the symbol of the people and men of Jerusalem before which Christ stood. The mountain was the symbol of the sanctuary / temple of Jerusalem, what had been God's house that men had made into a place of buying and selling.
The withering of the fig tree was the judgment Christ pronounced against Jerusalem - Matt. 23:37-38.
"37 O Jerusalem, Jerusalem, thou that killest the prophets, and stonest them which are sent unto thee, how often would I have gathered thy children together, even as a hen gathereth her chickens under her wings, and ye would not! 38 Behold, your house is left unto you desolate." (KJV)
"Your house". Those very words proclaimed that the temple was no longer God's house, no longer God's holy mountain. Just as God's Spirit had left that house before the Babylonian captivity as Ezekiel had seen in his vision in Ezek. 10:1-19; 11:22-23, YHVH's Spirit no longer occupied that temple when Christ cried over them in 30-31 AD.
The mountain the disciples could move by faith was the kingdom of Judah, and the temple. By preaching the gospel of Christ, the disciples would move the hearts of men and change kingdoms of wicked men into righteous nations, and righteous people.
Casting that mountain into the sea was the prophesy of casting down the nation of Judea which happened at the destruction of Jerusalem and all Palestine in the Roman-Jewish wars of AD 67-70. And the fruit of the fig tree was removed from Jerusalem "forever".
The righteous men and women of God are now to be found in every nation on earth, for all those in Christ (Gal. 3:26-29) as all those in Christ are now counted for the seed of Abraham, and are now the Israel of God.
(All bold emphasis is mine.)