Fruit and flowers
|The small orange fruits of G. tinctoria|
Growing on the north side of the house, in constant shade, is proof that autumn is still a time for flowers – Begonia grandis. This is a woodland plant from southern China and its pretty pink flowers are only one part of this plant’s colourful display. Turn the leaves over and an extraordinary cinnamon red is revealed.
|Flower of B. grandis with the colourful dark underside|
of the plant's leaves in the background.
Nick then takes me around the corner to one of his favourite plants in the garden, Impatiens tinctoria – a balsam. I can instantly see why it’s a favourite as the flower is truly stunning. Native to the mountains of western Ethiopa, this plant is adapted to cold dry winters and warm wet summers. The plant towers above me and Nick tells me all this growth has happened since the second week of May – an extremely fast growing plant indeed!
|Flower of Impatiens tinctoria.|
Like all balsams, I. tinctoria has an explosive seed capsule. Each one is about 3cm long (just over an inch) and resembles a tiny cucumber. Water pressure keeps the capsule extended, but when a little force is applied, the sides of the capsule spring into their natural curled state of repose and the seeds are literally catapulted out. This explosive dispersal method is partly why Impatiens is very successful as a genus. However, this beauty is not to be confused with Impatiens glandulifera (Himalayan balsam), which was introduced as a garden ornamental by the Victorians and is now found choking many of the waterways throughout the UK.
|The bladder-like fruits of Colutea arborescens|
Besides the fruits, flowers and seeds, there is no denying that the Botanic Garden also offers a colourful display of leaves at this time of year. All the autumn colours are represented – yellows, oranges and even vibrant reds.
As the days get shorter, many plants stop producing a type of plant hormone known as auxin. Among their many roles, auxins prevent a specialised layer of cells at the base of the leaf stalk – the abscission layer – from developing completely and cutting off the internal tubes that connect the leaf to the rest of the plant. So, once auxin levels drop, the abscission layer functionally cuts the leaf off from the rest of the plant. The chlorophyll, which gives the leaves their green colour, disintegrates rapidly revealing the other pigments carotene and anthocyanin, giving the leaves their autumn colours.
|The bright orange seed of E. alatus seems dull compared|
to the vibrant colour of the leaves
Other plants, such as the witch hazel, (Hamamelis mollis ‘Pallida’), don more golden hues but are no less spectacular.
|H. mollis glowing gold against the evergreen backdrop|
of Atriplex humilis (Fat Hen family)
Remember - next weekend (26th-28th October) is the 25th British Orchid congress at Writhlington School!