And purple loosestrife, that European native that has made itself very much at home in North America, to the extent that many people consider the plant a pernicious weed.
But consider this.
Inside each loosestrife blossom, the sexual organs come in three different lengths: short, medium, long. These are arranged male-male-female, male-female-male, or female-male-male. All blossoms on any one loosestrife plant are of the same kind, as one can ascertain with a bit of patience and a magnifier.
Now here's the clever thing: A plant can only be fertilized when pollen from a male part lands on a female part of the same length. This means a plant can never fertilize itself, because only a different plant will have a male part of the same length as the female part.
This guarantees cross-pollination between plants, which confers evolutionary advantages. Cross-pollinated plants are often better adapted to survival and reproduction than either parent, and they avoid the genetic deterioration that sometimes results from inbreeding.
Imagine the exquisite molecular chemistry that regulates fertilization. The lock-and-key fit between loosestrife sperm and egg must be a thing of almost unbelievable subtlety and refinement.
In his delicious little book Saving Graces, the horticulturist Roger Swain tries to remember what it was like to be a sneaker-clad child in nature:
All of us are born wild-eyed, but our outlook changes with time. First you stop seeing camels in the clouds, then you outgrow the fear that there is a snake in your bed, then you learn that there aren't really alligators in the sewers. Plans to become a forest ranger disappear along with any chance of seeing an ivory-billed woodpecker. The expansive optimism of childhood becomes as limited as a two-week summer vacation.What a shame that we lose the ability to see wonders where everyone else see a weed.