40 NEBRASKAland • JULY 2015
M
ilkweed plants have recently
gained a lot of attention
because they are the plant
of choice for monarch butterfly
caterpillars. Loss of habitat and
changes in agricultural practices have
decreased milkweed populations across
the state, leaving fewer places for
monarchs to lay eggs.
At the same time, if you look at the
reproductive strategy for milkweed
plants, it's kind of shocking they've
survived as long as they have.
Milkweed pollination is literally (and
I don't mean that figuratively) a series
of accidents strung together. That any
milkweed plant produces seeds seems
nothing short of miraculous.
To start with, an insect has to be
attracted to the milkweed flower,
presumably by the sweet sugary nectar
inside. That's not difficult – many
insects enjoy sweets, and milkweed
nectar seems to be particularly tasty.
However, the next step requires the
insect to accidentally step into one of
the tiny slits between the anthers on the
side of a blossom. There is certainly
no incentive for the insect to do that,
in part because those slits can be tight
enough that insects can't always get
their leg back out.
Once the insect's leg is in the flower,
it will immediately try to extract it.
As it does so, it may snag a pair of
waxy orange gobs of pollen called
the "pollinia" with its foot. That's the
critical next step of the process for
the milkweed. If the insect pulls its
leg out without pollinia stuck to it, the
milkweed loses.
However, even if pollinia stick to the
leg of a visiting insect, the milkweed
hasn't yet won. In order to complete
the pollination process, the pollinia
have to be deposited inside a different
flower – hopefully on a different
milkweed plant altogether. This
requires a couple of things to happen;
the insect has to travel to a different
milkweed plant and it has to refrain
from removing what has to be a pretty
awkward sticky mass hanging off its
leg before it makes that trip.
Assuming an insect makes it to
another flower with the pollinia still
attached, there are still several steps
A Series of
Fortunate
Accidents
The pollination strategy for milkweed is so impossibly
crazy there's no way it should work.
By Chris Helzer
The abundance of milkweed seeds
floating around in the fall shows that
the accidental pollination strategy of
milkweed is successful.
This giant milkweed bug (on butterfly milkweed) already has pollinia stuck to two of its
legs.
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This giant milkweed bug (on butterfly milkweed) already has pollinia stuck to two of its
POLLINIA
The abundance of milkweed seeds
