PLANT growing isn’t represented at the Olympics. Perhaps the two-week time span of the modern games is too short to grow a gold medal specimen. But the International Horticultural Expo, often regarded as the Olympics of horticultural science, seems to whip up the kind of excitement among green-thumbed enthusiasts usually reserved for the quadrennial sporting fixture. Perhaps the two-week time span of the modern games is too short to grow a gold medal specimen. But the International Horticultural Expo, often regarded as the Olympics of horticultural science, seems to whip up the kind of excitement among green-thumbed enthusiasts usually for the quadrennial sporting fixture.