Unmistakable Tulip Tree poorly served by bees

I guess most readers will know the Tulip Tree, but part of my mission in life is to give all plants their moment in glory in my blog, whether rare or common, friend or foe, well known or largely unknown.

As is usually the case, it was a close encounter with the plant that prompted me to feature it here. In this case, in one of the beautiful private gardens of Mount Macedon, just north of Melbourne.

Liriodendron tulipifera is perhaps unmistakable. The softly lobed leaves are heart- or wedge-shaped in outline (Augustine Henry, see below, described the leaves of the related Chinese species goose-foot-shaped, which could also apply here) and the flowers, a rather photogenic cup of greenish yellow with a band of orange.

And if you think the flowers are like those of a Magnolia, you are on the right track. In the most extreme, and recent, classifications, Liriodendron and Magnolia are the only two genera in the family Magnoliaceae. More traditionally there were 11 or more genera, but all of these are now swallowed up by a mega-Magnolia. Liriodendron has always been distitive, in look and in the evolutionary trees based on comparing molecular sequences.

There are two species of Liriodendron. The first described was from eastern North America but described by Swedish biologist, Carl Linnaeus, in 1753. He named it the 'tulip-flowered lily-tree', Liliodendron tulipifera.

You can see here the ring of stamens (the male bits) around a collection of ovaries. The flower produces lots of nectar, attracting sufficient bees to create an industry in North America for Tulip Tree Honey. While the bees are good at gathering nectar they seem to be less effective as pollinators in Liriodendron tulipifera.

That's not the case in the other species. Over a century later, in 1875, the genus was collected from Lushan Mountain in Jiangxi (江西) Province, China. That first specimen was without flower or fruit and assumed to be the North American species, estabished in the forest from a garden escape.

It took a few more attempts to get material with flowers, eventually supplied by Augustine Henry, confirming that this was a distinct species, found in China and Vietnam. Liriodendron chinense has slightly different shaped leaves and no orange on the flower petals. It does, however, seem to be better served by bees (if not so well by visiting flies and beetles).

It is not surprising it took some time to recognise it as distinct. Even with flowers, there is considerable variability in leaf and flower shape and size within Liriodendron tulipifera. A dozen or so cultivars of this species available, plus a hybrid between the two species, aptly named Liriodendron x sinoamericanum.

Liridodendron tulipifera is not a species for our warming climate in Melbourne (over the last few years I've noticed a few failed plantings in my local suburb) but it is does extend over quite a wide range of climates in its natural habitat in North America. For example it can tolerate winter temperatures down to an average of -7 degrees C in New England and New York, and up to 27 degrees on average in Florida.

Which makes me think that it may continue to thrive in cooler mountain areas such as Mount Macedon if temperature rise only a few degrees over the next few decades. So for the sake of this beautiful garden plant, if not for the planet more generally, do all you can to slow the pace of climate change.