Plants that amaze

Trees are big and long lived but which are the biggest and the oldest? The tallest tree in the world is Hyperion, a coast redwood in California at a whopping 115 metres tall but the largest tree is General Sherman, a giant sequoia, at 1500 m³. The oldest tree is thought to be Methuselah, a great basin bristlecone pine, again in California, at an impressive 4,852 years old.

Dendrochronology, the science of dating the lives of trees, is made more difficult by older trees tending to split and die off in sections. This means that the range given for tree ages can be large. Britain’s oldest tree examples, the Llangernyw Yew in North Wales and the Fortingall Yew in Perthshire, are estimated to be anywhere between 1,500 to 5,000 years old!

The largest flower in the world is Rafflesia arnoldii. The flowers, which take a year to develop, are about a metre across and weigh up to 11 kg. It is endemic to Indonesia and, whilst it is a vascular plant, it has no chlorophyll and is parasitic with no visible leaves, stems or roots. The Titan Arum, Amorphophallus titanium, has the largest unbranched inflorescence in the world and is found in Sumatra and – closer to home – in Kew gardens! It can reach more than 3 metres tall and is also known as the’ corpse flower’ due to its strong smell of rotting flesh. This attracts insects that will pollinate the flowers.

Some plants have adapted to living in low nutrient soils by developing the ability to trap and absorb the nutrients of insects and other animals unfortunate enough to get caught. While we may be familiar with the venus fly trap, the traps of the pitcher plant, nepenthes, are perhaps more impressive. The UK also has its own native carnivorous plants – sundew, butterwort and bladderwort.

Plants have adapted to extremes of heat and cold, moisture and the lack of it. Cacti and succulents find ways of absorbing and storing water, enabling them to survive drought conditions. Bulbs also give a plant the ability to store food and water to survive periods of drought and low light. A sandwort, Arenaria, is recorded as the highest flowering plant in the world, growing at altitudes of over 6,000m.

The most recently evolved plants are orchids, with an unrivalled ability to hybridise in order to adapt to current conditions. While there are terrestrial orchids in the UK, many tropical countries have epiphytic orchids that have adapted to living in trees. The flowers of orchids are so unique and specialised that they are often only attractive to one particular species of insect to pollinate them, making them very vulnerable to extinction if that pollinator becomes endangered.

Oaks are in the genus Quercus which is in the beech family. There are 2 native oaks in Britain, the English Oak and the Sessile Oak, but there are many more species which can be found in parks, urban settings and botanical gardens. The oak is known for its longevity and there are a number of ‘famous’ oaks in Britain including:

• Bowthorpe Oak in Lincolnshire which is over 1,000 years old and, with a girth of 12.8 metres, is considered the largest English oak in the country
• Gilwell Oak which stands in the grounds of The Scout Association’s headquarters at Gilwell Park and is reported to have inspired Robert Baden Powell, founder of the Scouting movement, to create ‘the moral of the acorn and the oak’, an analogy for the growth of the Scout movement and a lesson to young scouts that small things can grow to be strong and powerful.
• Major Oak in Sherwood Forest which, according to local folklore, provided shelter to Robin Hood and his band of Merry Men who slept on its sturdy branches.

Contorted or corkscrew shrubs are popular features, few more so than the corkscrew hazel or Harry Lauder's walking stick. The hazel species, C. avellana, is too large for most gardens except in boundary hedges, but many garden varieties are more restrained.

The corkscrew hazel will ultimately reach 5m (20ft), but only half that in 25 years because it is slow-growing. Winter is its season, when the curiously contorted stems stand out against a clear sky and then develop their fine catkins before the spring foliage appears. Fully hardy, this shrub prefers sunny or semi-shaded sites in fertile, well-drained soil.

Foxgloves and veronica are both examples of plants commonly affected by fasciation. Fasciation is where flattened, elongated shoots and flower heads look like many stems compressed together. This strange-looking problem may be ugly or attractive, but is always interesting.

Fasciated stems are produced due to abnormal activity in the growing tip of the plant. Often, an abnormal number of flowers are produced on affected stems. Ring fasciation is where a ring of flowerheads are produced around a normal central flower, a phenomenon referred to as ‘hen and chicks’.

Whilst fasciation is unpredictable and usually limited to a single stem, foxgloves and veronica are plants commonly affected by it as well as delphiniums, euphorbias, forsythia, lilies and primulas.