Fructans are a type of storage carbohydrates found in grasses, particularly in the cool season grasses growing in temperate climates common in northern Europe or North America. Fructans are made of several units of fructose (a monoaccharide) attached to a sucrose molecule (a disaccharide). 

Fructans can be produced by plants even when temperatures are too low for growth (in fact, it can make a plant more able to tolerate freezing temperatures), which is why high levels of fructans can accumulate on cold sunny days.