This year, we are expecting multiple flowers for the first time on our Amazon Moonflower – Strophocactus wittii. We shared the news on social media mid-January, asking our followers what they would call a group of Moonflower buds. The most popular suggestion was a ‘lunation’!
What is Strophocactus wittii - the Moonflower?
Strophocactus wittii, formerly Selenicereus wittii, is a flowering cactus from the Amazon rainforest. It is a species of plant in the genus Strophocactus and in the cactus family (Cactaceae). It is one of several species commonly called ‘moonflowers’. It was first described in 1900 and is one of three species of cactus found in the central Amazon basin.
Where and how does Strophocactus wittii grow?
Strophocactus wittii, is found in swampy rainforests near Manaus, Brazil where it grows in the forests of the Amazon basin, which are regularly flooded for a few weeks each year. During this time, the Strophocactus wittii seeds are spread via the water, which is unique within the cactus family.
When we think of a cactus, we usually imagine a spiky plant with a thick stem from a dry and arid environment like the desert. The Moonflower couldn’t be more different! It is epiphytic – which means it relies on another plant as a structure on which to grow. Its stems look like flattened pads and leaf-like as they climb and twine their way around their host plant, with roots gripping the host’s trunk. Here at CUBG, the water chestnut (Pachira aquatica) in the Tropics House acts as its host.
While the Amazon Moonflower isn’t rare in the wild, it is rare in cultivation and requires expertise and the right conditions to thrive. This species of Strophocactus is grown in 30 botanic gardens globally, including the Royal Botanic Gardens, Kew and Birmingham Botanical Gardens in the UK. Cambridge University Botanic Garden was the first UK Botanic Garden to have a moonflower bloom (which happened in 2021). We shared plant material with Royal Botanic Gardens, Kew in 2022.
What are the signs that it is ready to flower?
This year we have four developing buds, on 30 January, these were measuring at: Flower A (the highest flower) 29cm; Flower B 26cm; Flower C 20cm and Flower D 17cm. We are expecting them to flower very soon as the buds are swelling and the pedicels (flower stalks) are beginning to lower, which is a sign it is getting ready to flower.
Kathryn Bray, Glasshouse Senior Horticulturist, says: “We first noticed multiple buds developing in the summer. When they are small it is difficult to distinguish between vegetative and flower buds. When they began to develop a point, we were certain they were flower buds. Currently we have four at the later stages of development and multiple others that will probably flower later in the year.
The buds sit at a few centimetres for many months, and then when growth starts, it happens quickly. We have seen the flower stalk lowering every morning, and this is even more apparent when watching the time lapse footage we are recording. The buds are definitely fattening and we are expecting them to open in the next few days.”
What happens when it flowers?
Individual flowers open for one night only. Flowering in the wild begins after sunset and flowers are fully expanded about two hours later. They start to close again at sunrise. Our past couple of flowerings have taken place in the afternoon.
The flower is known to give off a strong, sweetly scented perfume before it opens. This is to attract pollinators in the wild. It is believed to be pollinated exclusively by two species of night flying hawkmoth. Both of these have incredibly long proboscises (tongues), which collect nectar produced by the flower. In the act of collecting this nectar, the flower is pollinated.
The team do not plan to hand pollinate it, as their understanding is that Strophocactus is self-incompatible. They will collect and store some pollen though, to potentially share with other botanic gardens. They will also take samples of some of the petals. CUBG’s artist-in-residence, Nabil Ali, who is creating a catalogue of natural plant dyes using the Garden’s plant collection, will use some of these to see what pigment comes from this unusual and enigmatic flower.
Can I come and see it?
Yes, but only during normal opening hours. Visitors will find it in the Tropics House of the Glasshouse Range. The Glasshouses currently close at 3.30pm, so we have set up a web cam, so that keen moonflower enthusiasts can watch outside of opening hours, which is when we expect the flowers to bloom.
Please note, due to essential works to the Glasshouse Range structure, scaffolding is being erected over the Continents Apart House from 7/2/24 and we will have to close other areas as necessary. These works will not affect the viewing of the Moonflower at present and we will try to keep as much of the Glasshouse Range open to visitors as is safe and possible to do so, letting you know when an area is closed. Thank you for your understanding.