letting nature back in

Of the 270 naturally occurring species of pelargoniums in the world, about 219 species occur in South Africa. Of these, I focus here on just two – and one hybrid – that grow in our garden. And a true geranium also makes an appearance. Be it the leaves, the flowers or the seeds, pelargoniums are always interesting to photograph.

Above are flowers of the rose-scented or coast pelargonium (pelargonium capitatum) growing in our garden. It grows naturally in coastal areas near to us in the Overberg, and in fact in coastal regions from the west to the east of South Africa, including on sand dunes and low hillsides.

The flowers are relatively understated and lack the strong scent of the leaves and stems, but they still attract the attention of insects, including butterflies.

The butterfly that I regularly see visiting the plant in our garden in the early summer months, is a geranium bronze butterfly. It is most likely the common geranium bronze (Cacyreus marshalli), a small butterfly with a wingspan of 15–27 mm (0.5–1 inch). There is a chance that I also see the similar but less common Dickson’s geranium bronze (Cacyreus dicksoni), which also occurs in this area.

I had assumed that the butterflies were visiting the flowers to feed on nectar, but I have since learned that pelargoniums (rather than true geraniums) are host plants for the larvae of geranium bronze butterflies. So, the butterflies are visiting not to nectar, but to lay their eggs on the flowers and stems as their larvae feed exclusively on pelargonium plants.

The common geranium bronze butterfly (Cacyreus marshalli) is native to southern Africa, but unfortunately it was inadvertently introduced into Europe via the trade in pelargoniums. It is (or was in 2022) the only non-native butterfly species recorded among 482 European species (Rocchia et al., 2022).

Through ongoing trade in non-native pelargoniums that are used as much-prized ornamentals, the common geranium bronze butterflies are spreading through warmer regions in Europe. With no natural predators in Europe, the larvae do significant damage to ornamentals in nurseries and gardens. The larvae bore into the stems of the host plant, which they eat from the inside, causing the stems to weaken and blacken. In South Africa it is thought that their presence is limited by the presence of natural predators or parasitoids, and consequently damage to plants is limited too.

The increasing presence in parts of Europe of common geranium bronzes could become a threat to native biodiversity with the possibility of the butterfly being further naturalised if it adapts to wild geranium species as hosts.

These butterflies thrive in warmer temperatures and so far, their spread is contained by the colder temperatures at higher elevations, for example in Alpine regions in Italy. But, there is a fear that as climate change leads to higher temperatures, common geranium bronzes may then be able to survive in Alpine areas, posing a threat to less adaptable native species of butterfly and to wild plants in the Geranium family (Geraniaceae), even at higher altitudes.

The rose-scented pelargonium (Pelargonium capitatum) has many cultivars and hybrids. In addition to being grown as an ornamental plant, it – like other species of scented pelargoniums – is also cultivated for its oil of geranium, which is used in perfumes and cosmetics.

The scented leaves can be used as a skin softener by rubbing them on calluses and hard skin on the hands and feet. The leaves can also be used in bath water to help soothe skin rashes. Traditionally a tea made from the leaves was used to treat digestive, kidney and bladder ailments.

As the flower fades, the beak-like fruits or seed capsules emerge. The name Pelargonium derives from the Greek pelargós, meaning ‘stork’, because the seeds look like a stork’s beak.

As the fruits ripen, they gradually split releasing elongated seeds that are attached via a spirally stem to a fluffy ‘tail’.

The above photo is of the seedy remains of two flowerheads showing the elongated seeds attached by spirals to the fluffy tail-like structures. The small blue flowers are a species of wild lobelias that have arrived in our garden as very welcome ‘volunteers’.

When the seeds of the rose-scented pelargonium eventually detach from the beak-like fruit, they can float off through the air, and after falling to the ground the spiral stem can effectively corkscrew the seed into the ground as the fluffy tail is turned by the wind.

Above (and in the header photo) is a close-up of the elongated seed and the spiral or ‘corkscrew’ structure with the fluffy tail.

The only true geranium in our garden, as opposed to a pelargonium, is the low-growing Geranium incanum with its lovely open purple-coloured flowers (above). Known as the carpet geranium, it is useful in the garden as a pleasing groundcover. It occurs naturally as a low scrambler in sandy or stony grounds in coastal regions of the southwestern and eastern parts of South Africa.

The name ‘geranium’ comes from the Greek géranos, which refers to a crane, as the seed capsule resembles the beak of that bird. Originally, pelargoniums were not distinguished from geraniums, which perhaps explains why pelargoniums are often referred to as geraniums. But there are sufficient differences that pelargoniums have been split from geraniums into a separate genus. Naming the beak-shaped fruit of the pelargonium after the stork, was a way of differentiating it from the geranium, which is named after the crane, though in fact their structures are very similar.

One of the most obvious differences between the two genera is that geranium flowers are radially symmetrical (5 petals of similar size and shape) and pelargonium flowers are asymmetrical, with 2 upper petals different in size and shape to 3 lower petals, although that characteristic has been bred out in some hybrid species.

The showy Perlargonium cucullatum is known as the hooded-leaf pelargonium or wild malva and it makes a fine display in our garden in early summer. It can also be found growing wild and abundantly in the southwestern Cape. For more on this species see an earlier post of mine, Pelargoniums wild and domesticated

The species part of the name of this plant derives from the Latin word cucullatus, meaning a cape or cowl, reflecting the cup-shaped leaves. The attractive leaves produce a sweet smell when crushed, and they are used in a traditional medicine for coughs and chest congestion.

When bearing pollen, the stamens of the flowers are an unexpected orange in colour.

The rather hairy and deep purpley-magenta casing or calyx of the fruiting capsules almost matching the colour of the veins on the flower petals.

I photographed a large cabbage white butterfly (Pieris brassicae) visiting a flower of the Pelargonium cucullatum to feed on nectar. Pelargoniums are not a host plant of the larvae of this species of butterfly. In our garden the caterpillars feed mostly on nasturtium plants. Large cabbage whites are not indigenous to South Africa. I intend posting about these potentially invasive butterflies in the near future.

Last summer I was given some pelargonium cuttings that I planted in our garden. One of them turned out to be this hybrid species of regal pelargonium with wine-coloured flowers (above).  I gather that regal pelargoniums (known as Martha Washington in North America if I understand correctly) originate from hybridising Pelargonium cucullatum and Pelargonium grandiflorum, which are both native to the Western Cape in South Africa. Coincidentally, this regal pelargonium in our garden grows right next to one of its parent plants, the Pelargonium cucullatum.

Sources:

Adams, Trevor. 2005. Pelargonium capitatum. PlantZAfrica. South African National Biodiversity Institute (SANBI). https://pza.sanbi.org/pelargonium-capitatum

Favilli, Leonardo & Manganelli, Giuseppe. 2006. Life history of Cacyreus marshalli, a South African species recently introduced into Italy (Lepidoptera Lycaenidae). https://www.researchgate.net/publication/342439329_Life_history_of_Cacyreus_marshalli_a_South_African_species_recently_introduced_into_Italy_Lepidoptera_Lycaenidae

May, Liesl. 2000. Pelargonium cucullatum. PlantZAfrica. South African National Biodiversity Institute (SANBI). https://pza.sanbi.org/pelargonium-cucullatum

Rocchia E, Luppi M, Paradiso F, Ghidotti S, Martelli F, Cerrato C, Viterbi R, Bonelli S. 2022. Distribution Drivers of the Alien Butterfly Geranium Bronze (Cacyreus marshalli) in an Alpine Protected Area and Indications for an Effective Management. Biology (Basel). Apr 7;11(4):563. doi: 10.3390/biology11040563. https://pmc.ncbi.nlm.nih.gov/articles/PMC9027867/

Posted by Carol