weeds can be minimized with lower growth (weeds inherit their parents growth stat) and higher resistance(takes longer for weeds to overrun plants giving you time to catch it) if you want low maintenance plants. alblaka said himself that red wheat is picky about its light level.
yap. thats the reason why you should stronger your plants. otherwize if there is some sort of stuff to kill weed automativaly there would be no reason for resistance to be.