An interesting historical context regarding easy to farm ground: In New Zealand, before European settlement, the Maori could grow crops extremely easily. The country was mostly forest, and there were few grasses or other such open-ground plants that compete with crops as "weeds". This meant that the Maori could clear some soil, plant their kumara (sweet potato), and it would grow easily. They didn't have to constantly weed it, but could just leave the crop from planting to harvest. They had a very easy lifestyle in many ways - I have read of men planting the crops, then walking hundreds of kilometres barefoot through the bush for several months to attend meetings with other tribes, wearing only a shirt and carrying no provisions, returning home in time for harvest. Or (sadly in other cases) planting the crop then going to war, and stopping fighting in time for harvest.
European settlers brought grasses for grazing animals, and other such plants, and the environment completely changed. Now the same crops are more difficult to grow as there are so many more weeds to control.
I see the ground in Eden as similar to the forest soils of early New Zealand - fertile, weed-free, and easy to crop. The curse was largely the introduction of weeds (illustrated by thorns and thistles, but possibly including others), that turned agriculture into back-breaking labour for Adam and his descendents. The curse could have been the spreading of such seed.
Maybe God is saying that He will not curse agriculture by spreading weeds deliberately? That would mean that man today will still generally be dealing with the residual effects of that curse (the existence of weeds), but in some cases may find or create a situation where they are eliminated and agriculture becomes easy again.
Such as this.