[Genesis 3:18]

Both thorns and thistles it shall bring forth for you, And you shall eat the herb of the field. [NKJV]

It will produce weeds and thorns, and you will have to eat wild plants. [GNT]

Both thorns and thistles it will yield for you, and you will eat the plants of the field. [BSB]

REAPING WHERE ONE DID NOT SOW

In principle of God's Judgment, "What a man sows, he'll reap." But in the Bible verse above, Adam would be reaping the thorns and thistles he did not sow and eating the herbs he did not plant.

[Matthew 25:24] — "Then he which had received the one talent came and said, Lord, I knew You that You are an hard Man, reaping where You have not sown, and gathering where You have not strewed:"

This could mean a blessing or curse, a garden of Eden or desert. Adam experienced it (reaping where he did not sow) both as a blessing and later as a curse, both as a garden of Eden and later as a desert. In the top Bible verse above, God was reversing it from being a blessing to becoming a curse, from a garden of Eden (blessed ground) where the ground produced trees for Adam and he ate fruits to a cursed ground where the ground produced thorns and thistles for Adam and he ate herbs instead of fruits.

[Hebrews 6:7-8 BSB'19] — "For land that drinks in the rain often falling on it and that produces a crop useful to those for whom it is tended receives the blessing of God. But land that produces thorns and thistles is worthless, and its curse is imminent. In the end it will be burned."
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The ground that was cursed for Adam's sake would still have the Fertility or productive capacity to yield or bear thorns, thistles, wild plants or wild herbs and even poisonous plants, etc, but would not easily yield the fruits of what Adam would sow in it. This means, when God cursed the ground for Adam's sake, the curse did not disable the ground's productive strength; instead the ground also produced offsprings and harvests for the curse, for the curse of the ground for Adam's sake became seed sown.

So that curse was not just destructive, but reproductive and multiplicative, having abilities to grow descendants or offsprings. The curse is like the tares the enemy planted in the field, while the ground is like the field: and the Lord said, "Let them grow together with the good plants until the harvest…" So the same fertility and strength the ground assigns to the good plants, it also assigns to the evil or cursed plants. Whatever gets sown is entitled to getting reaped or growths.

Be not deceived, "Whatever a man sows, that shall he also reap." [Galatians 6:7]. But Adam did not sow the curse nor the thorns/thistles, yet even those things he did not sowed he would reap together with eating herbs he did not sow. That's because the curse that sowed those things in the ground is "Curse for Adam's sake." He did not sow the "Curse," but sowed the "Cause for the Curse" which is same as sowing the Curse.

[Jeremiah 12:10,13] — "Many Pastors have destroyed My vineyard, they have trodden My portion under foot, they have made My pleasant portion a desolate wilderness. … They have sown wheat, but shall reap thorns: they have put themselves to pain, but shall not profit: and they shall be ashamed of your revenues because of the fierce anger of the LORD."

Causing the anger of the Lord to come is a way of reaping thorns (curse) which you did not sow. Let it not be for your sake or your cause why God's fierce and destructive anger is sown as curse or plague on earth.

Please add Mosquitoes to the list of thorns and thistles mankind are experiencing, after all Mosquitoes have their stingers as thorns, thistles or needed syringes that takes away good blood from people and animals, and inject parasites into them instead. Therefore, Mosquitoes are injections and thorns but are evil injections because they are not injecting herbs (medicines) into people as thorns/thistles, but injecting sicknesses and parasites.