When we first moved to North Idaho, the deep green spring pasture looked like a blessing. After years in Kansas and Colorado, I had never heard of cheat grass, so I admired the lush growth—until a neighbor stopped by and informed me that our beautiful field was actually an invasive pest.

Around here, everybody knows cheat grass except the newcomer praising it. Like fool’s gold, it succeeds by appearance. It looks valuable at first, then reveals itself later as dry, troublesome, sharp, and stubborn.

Experts offer complicated plans and cheerful wishes of “good luck,” but many landowners simply learn to manage it one season at a time. The lesson reaches beyond weeds.

Fool’s gold and cheat grass both remind us that not everything bright or green is good. As Scripture says, “You will know them by their fruits.” Some things require ...