Friday, 10 August 2012

Giant water lilies, scarab beetles and sublime aquatics..

The Lily Tank in the Lily House is burgeoning and looking suitably exotic this week. The star of the show is the giant water lily, Victoria cruziana, which is in flower for the second time this year. This plant hails from South America and produces enormous floating leaves up to to 2.5m across. We grow it as an annual plant, sowing the pea-sized seeds in February and then plant out in the Lily Tank in April. The flowers open at night (or late in the day), each one lasting only two days. 

Victoria cruziana
On the first night of opening the flower is a pure white, this attracts the scarab beetle pollinator (Cylocephata castaneal) in the wild. At this point the female organs of the flower are receptive to pollen, but the flower's own male organs are not yet active. On the second night the flower changes to a pink-plum colour. At this stage the female organs are no longer receptive, but the male anthers are shedding pollen in abundance. In the wild the night flying beetle enters the flower on the first night, feeds on nectar through the day and then escapes on the second night covered in pollen. The beetle then visits another white flower promoting cross pollination.

Noah Walker at 10 weeks

There are many stories telling of floating young children on these leaves, we thought an experiment was required to test the theories. Back in 2001 new born Noah Walker, son of our Director Timothy Walker, was happily floated on one of the Victoria leaves. This made headline news in the Oxford Mail and prompted renewed interest in this tropical behemoth.

Noah Walker, August 2008
Some seven years later the question "just how much weight can a leaf support" was posed. Once again Noah willingly found himself the guinea pig. On a warm August day in 2008 Noah was again successfully floated on the leaf of Victoria.
Not wanting to stop there, Jonah, Noah's older brother, volunteered his services. Unfortunately on this occasion Jonah sank. So, in conclusion, the optimum load bearing capacity is somewhere between the weight of a seven and nine year old.

Nymphaea x daubenyana

Other plants of interest in the Lily Tank include Nymphaea x daubenyana, a hybrid that arose in this tank in 1874 and named in honour of Professor Charles Daubeny, a previous keeper of the Botanic Garden who installed the tank in 1851. Oryza sativa, cultivated rice, is grown along the margins, a plant that sustains 50% of the World's population as a staple food crop. A large stand of papyrus reed, Cyperus papyrus, occupies one corner of the tank. This is the plant used by the ancient Egyptians to manufacture papyrus parchment paper. Once common along the River Nile, it is now largely absent due to competition from invasive species.

Oryza sativa

Come down to the Botanic Garden and take a look for yourself. If you are in luck you might catch Victoria in flower.

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