Here's my own peculiar contribution on this subject, from 2009:

The Holly is the Ilex

Oh, the holly bears a berry that is three per-cent fat,
As a fraction of the dry weight. It is measured like that
Because moisture content varies. There is much water lost
In the sereness of the winter, in the season of frost.

   Oh, the holly and the ivy, being natural plants,
   Have conserved the best mutations that arose once by chance.

Oh, the holly’s an example of an angiosperm:
For a plant producing flowers, that’s the botanist’s term.
Therefore holly is a hardwood, unlike cedar or pine,
In the prime classification lumber merchants assign.

Oh, the holly is a dicot. That's the term that we use
For a plant which, when it’s sprouting, puts forth seed leaves in twos.
It has classic dicot features: pollen grains with three pores,
Leaves in which the veins are pinnate, flower petals in fours.

Oh, the holly is the Ilex, though there’s more than one kind.
Aquifolium is the species that in England you’ll find,
But in other ecosystems different species are seen.
Yerba maté, from the tropics, is a source of caffeine.

Oh, the holly has a berry that is heavy and needs
Active transport by wild creatures to distribute its seeds.
Though the berry is too bitter and too hard to eat fresh,
Nights of frost improve its flavour while they soften its flesh.

Oh, the holly is dioecious. You will note, if astute,
Half the plants have male flowers, and they never set fruit.
Since this fact is as important as the berries’ red hue,
You might think old songs would note it, but we’ve found none that do.



There are links to the songsheet (music, lyrics, and some reference notes) and an .mp3 here.