Sunflowers are big, but they aren't among the largest flowers in the world. In fact, the largest blooms have names you've probably never heard of before, some flower plants growing up to 15 feet tall, or having blooms that grow 3 feet in diameter. Some of these giants have a pungent sent when blooming, but it's not pleasant; even if your location has a climate that suits these flowers, you may not want them growing in your home garden.
This flower is touted as having the largest bloom of all flowers. It comes from the Indonesian rainforests, weighing up to 15 lbs. and growing as much as 3 feet across. You would think a flower of this size would grow on a huge plant, but not so. The Rafflesia arnoldii is actually a parasitic plant. This means that it attaches itself to other plants and grows there, taking nutrients and moisture from the host plant. To attract pollinating insects, the flower spews off a scent of rotten flesh.
Another Indonesian grown flower, the Amorphophallus titanium, is also known as Titan arum or the corpse flower. It uses the same type of scent as the Rafflesia arnoldii, of rotten flesh, to attract pollinators to it's bloom. It gives the appearance of one large flower, but it's actually many small flowers. This type of flower is called an inflorescence. The plant can reach heights of between 7 and 12 feet, weighing as much as 170 lbs. The deep purplish-red bloom only lasts a couple of days.
The giant hogweed, with inflorescence blooms that are 2 ½ feet wide, form a dome-shape that looks much like a white umbrella. The hollow stems grow up to 15 feet and up to 4 inches across. It is a native Eurasian plant that first showed up in America as an ornamental flower grown in New York in 1917. It has since been listed as a federal noxious weed. It tends to crowd out other plant life and causes a health risk to humans. An element in the sap, furocoumarins, can cause skin irritation. Eye contact causes temporary and sometimes permanent blindness. It is against the law to plant, propagate, sell or transport the giant hogweed in the United States.