This is the plant. It is miner’s lettuce, also known as wild lettuce or prickly lettuce. As can be seen in the picture, the pavement appears solid. There is actually a very small hole, about an eighth of an inch in diameter, that the seed was apparently able to find.
Although miner’s lettuce is considered to be a weed, it is a hardy one. This plant is quite healthy and about 18 inches tall. Two other plants can be seen in the picture. One is another miner’s lettuce plant right next to the pylon and the other is wild mustard.
All three plants are growing through tiny holes in the pavement, despite the inhospitable location.