God has seeded His church with vessels for honor—the wheat—while Satan has sprinkled in his own vessels for dishonor—the tares (see II Timothy 2:20-21). Jesus does not use the imagery of wheat and tares haphazardly to relate this important lesson. Instead, the physical properties of these two different plants reveal a depth to the parable's symbolism that emphasizes how different in quality the wheat is from the tare, and how hard it is to tell them apart.
Wheat, which Christ uses to symbolize His true children, has always been a vital, life-giving substance, possessing both nutrition and healing properties. During most of human history, it has most commonly been used for bread, and it has long been called "the staff of life." Herbert W. Armstrong even proclaimed, "The grain of wheat God causes to grow out of the ground is a perfect food." The matchless quality of wheat serves as a symbol revealing how highly God regards His children.
In contrast, Christ uses the tare to symbolize counterfeits within His church. Tares are weeds diametrically opposite to wheat in all their properties other than appearance. Even the botanical name of the weed, darnel, conveys its detrimental quality. Darnel comes from the French language, meaning "drunkenness," having earned this name as a result of its intoxicating effect when consumed.
When darnel is ground into flour, baked in bread, and consumed while hot, the eater may experience symptoms similar to drunkenness, including trembling, followed by an inability to walk, hindered speech, and vomiting. In addition, darnel is commonly infected by the ergot fungus, which can cause hallucinations when consumed in small doses, but in large doses can do heavy damage to the central nervous system. The Greeks and Romans supposed the darnel and the fungus to cause blindness. The Romans even crafted an insult from darnel, lolio victitare, "to live on darnel," a phrase applied to a dim-sighted or shortsighted person.
The high value and health properties of wheat are opposite to the common and harmful properties of darnel, yet in Christ's parable the owner of the field allows both to grow together. One reason is because wheat and darnel are exact in their appearances during growth. Both plants are lush green and can be distinguished only when they mature and produce fruit: Wheat berries are large and golden, while darnel berries are small and gray. Thus, if the farmer attempted to uproot the tares before maturity, he would wreak havoc on his wheat. Today, modern harvesting equipment easily sifts between the two because of their different sizes.
Spiritual wheat and tares grow alike within God's church, identical in appearance, and to attempt to uproot the tares would result in uprooting some of the wheat as well. Just as the qualitative difference between the mature fruit of wheat and darnel is different, only by the fruit may the brethren be known (Matthew 7:15-20). Even after maturity, God Himself—and no one else—will have the tares removed and will destroy them in the furnace (Matthew 13:30).