Plant of the Week, 1st January 2024 – Ipomoea indica (Blue Morning Glory)

Last week we were in Melbourne, Australia. It’s a big bustling city with a large and leafy suburban area. I love to walk along the pavements spotting the frequent ‘weeds’ that have arrived from many parts of the world. Most of them are European, and the common British species are especially well represented, occupying similar habitats as they do back home.

The metro train from my daughter’s house to the city centre takes less than 20 minutes, and there are opportunities to botanise on the way. One day last week, as we approached the Melbourne Cricket Ground and the train slowed down I glimpsed two distant telegraph poles festooned with Morning Glory, looking like a pair of totem poles. Alas, by the time I had my camera phone ready it was too late. I missed them.

Sitting on the fence. Stems are entangled to form an almost solid wall of vegetation. Photo: John Grace.

Later, walking in the suburb of Fairfield, I saw the species again, this time scrambling up a fence in a quiet lane. I took the photos you see in this article, and identified the plant as Ipomoea indica. Despite its name ‘indica’ the species is believed to come from the Americas.  I have my doubts. Some authorities consider the species to be native in Australia. I consulted the on-line herbarium of the Natural History Museum (London) and discovered that one of their 143 preserved specimens of Ipomoea indica was collected in Eastern Australia by Joseph Banks & Daniel Solander during James Cook’s voyage of discovery in 1770. You can view the historic herbarium sheet here.

A feature of this species is that several flower buds are produced to form a bunch known as a ‘congested inflorescence’. Usually, only one becomes a flower. Note: the flowers may become paler later in the day. Photo: John Grace.

The Banks & Solander specimen dated 1770 is of course a mystery. Then, very few foreign feet had trod on Australian soil since the colonisation by aboriginal populations some time between 46,200 and 51,100 years ago. It is believed these people came in small boats from Asia. Perhaps they brought plants with them for food and medicine. In this hypothesis the native land of the species may have been India not the Americas. Another possibility is that the Ipomoea genus was present in Australia soon after the Angiosperms appeared on Earth (from 145 million to 100 years ago, and just before the break up of Gondwana when Australia become isolated). However, this is unlikely: molecular phylogeny suggests that the genus Ipomoea appeared only 35 million years ago. A more prosaic possibility is that Banks & Solander collected the material somewhere else along their journey (S. America, S. Africa, Tahiti) and simply got their labels mixed up.

The leaves are mostly three-lobed but can also be heart-shaped. Photo: John Grace.

The plant belongs to the Convolvulaceae as you may have guessed from its trumpet-like flowers and its tendency to entwine its stems around practically anything and climb fast. Its growth habit and general appearance is much like our own species of Calystegia and Convolvulus. Like these, it has the potential to be a very troublesome and pervasive perennial weed when given fertile moist soil with full sun. An assessment of its weed potential in Australia, and details of its biology, are given by Csurhes (2018) on behalf of the Department of Agriculture and Fisheries of the State of Queensland. It seems to be especially troublesome around waterways.

Demonstration of climbing ability. Left: stems curling (anti-clockwise when viewed from above). Right: stems entwined on a nearby fleabane. Photos: John Grace.

There are over 600 species of Ipomoea. They tend to occur mostly in tropical and subtropical regions, and a few have been cultivated for food (eg sweet potato). Ornamental cultivars are widely available. The taxonomy can be confusing because many species have synonyms. Ipomoea indica has been Convolvulus indica, for example, and sometimes Pharbitis indica. Seed merchants in Britain and elsewhere offer ‘Morning Glory’ seeds without telling the buyer which of the several possible ipomoeas are in the packet. The seeds could be cultivars of Ipomoea purpurea, the Purple Morning Glory; this one crops up as an alien in the British Isles.

Global distribution according to GBIF (Global Biodiversity Information Facility).

The shape of the ipomoea ‘trumpet’ flower resembles a solar collector. This deserves brief comment. Years ago, Sandra Patiño made careful observations of the angle of presentation relative to the position of the sun in the sky. The flowers track a position in the sky which is off-centre with respect to the sun. The hypothesis was that the intense sun’s rays would damage the reproductive organs if the trumpet pointed directly at the sun, but if a little off-centre there would be just a gentle warmth, speeding up development in the cool mornings (Patino et al 2002).

In the 1960s Morning Glory was considered as a ‘recreational drug’ with psychoactive effects similar to LSD. The active ingredient is the alkaloid ergine (D-lysergic acid amide known as LSA) present in the seeds. It happens to be one of the compounds also present in ergot of rye.

The route taken by the HMS Endeavour to and from Australia 1768 – 1771. Could the vessel have inadvertently brought plant material to Australia? Attribution: AlexiusHoratius at English Wikipedia, CC BY-SA 3.0 <https://creativecommons.org/licenses/by-sa/3.0&gt;, via Wikimedia Commons

References

Csurhes S (2016) Ipomoea indica, Blue Morning Glory. Department of Agriculture and Fisheries, Biosecurity Queensland.

Patiño S, Jeffree C and Grace J (2002) The ecological role of orientation in tropical convolvulaceous flowers. Oecologia 130, 373–379 DOI 10.1007/s00442-001-0824

©John Grace