The Internet’s a-buzz with news of Ron Sveden, the 75-year-old Cape Cod man who discovered that a growth in his lung was not, as feared, a tumor — but rather a pea plant. A seed had somehow lodged itself in his lung, presumably after some food found its way down the wrong tube, and the seed then sprouted.

But how is this possible? To grow, a plant needs warmth (check), moisture (check), and sunlight (ummmm…).The truth is that Sveden’s plant was in fact a mere sprout — about half an inch long when it was removed by a thoracic surgeon, according to the Cape Cod Times, which broke Sveden’s story early this week. When a pea seed germinates, typically it’s underground, in the soil. The seed has a little bit of energy stored in it to let the plant grow until it reaches the surface — although, yes, usually there’s a good deal of extra nourishment from nutrients in the soil as well. But it’s only when the shoot breaks through the surface of the soil, exposing itself to the sun’s rays, that photosynthesis can begin. Until this point the plant does not need direct sunlight. Afterward, the plant gets almost all of its energy to grow from the sun.

Even a half-inch sprout in the lung is enough to cause problems, of course. Sveden already suffers from emphysema and chronic obstructive pulmonary disease — serious lung conditions. But the sprout was removed without incident. Sveden is reportedly back to his usual self, and merrily eating peas once again.