Late Autumn Tree Colours – These photos were all taken on November 17th 2021. This year winds have been light and some trees have retained their leaves later than normal and with spectacular colouring. To learn more about why deciduous tree leaves change colour in autumn click HERE. Click on any photo to enlarge it.
These wild flowers were photographed in early July at the northern end of The Chilterns on a short walk to Ivinghoe Beacon – Pyramidal Orchid, Common Spotted orchid, Greater Knapweed, Self Heal, Agrimony, Goatsbeard, Mignonette, Dropwort and Clustered Bellflower. Ivinghoe Beacon is located on The Ridgeway which is an ancient track that runs through the Chilterns, an Area of Outstanding Natural Beauty AONB. The chalk grasslands along this route provide a wonderful habitat for wild flowers which are abundant in July. The flowers shown here are not rare but easy to see and photograph.
Click on any photo to enlarge it.
Two Orchids in flower in June :- The Greater Butterfly Orchid Platanthera chlorantha is found throughout Britain on grassy slopes and woods. It is fragrant at night and pollinated by night-flying moths. The Fragrant Orchid Gymnadenia conopsea is pollinated by butterflies and moths, attracted by its strong scent. It is found throughout Britain on grassland, especially on chalk or limestone and across northern Europe and western Asia.
Greater Butterfly Orchid
The orchid has a very long (26mm) slightly-curved spur at the back. The plant is up to 60cm tall and has 10 to 30 flowers on a spiked inflorescence. It produces nectar which is stored in the long spur.
The orchid has a short (16mm) strap-shaped labellum at the front. This is a close-up of the labellum and its entrance. Pollinia are white initially but turn brown with age as shown here. The pollinia are located either side of the spur entrance and stick to the large eyes on the side of the moth’s head, not to its proboscis.
The long (13mm) spurs are shown in this photo. Floral scent emission timing (day or night) may vary depending on the type of pollinator targeted. The orchid’s long spur is partly filled with nectar but only an insect with a long proboscis, such as the Hummingbird Hawk Moth or the Painted Lady can reach it. As the insect tries to reach the nectar, the pollinia are attached to its proboscis.
The Common Hazel is a wind pollinated, monoecious tree. A perfect flower, like those found on Cherry trees, has male and female parts combined but this can lead to self pollination so some trees separate the male and female flower parts. If the separated parts are on the same tree it is known as monoecious (Greek for one household). Alder, Oak, Beech, Birch, Hornbeam and Sweet Chestnut are other examples of monoecious trees.
Hazel catkins – the hazel is a monoecious tree with male flowers on hanging catkins and tiny female bud-like flowers with red stigmas. To see catkins on the closely-related Turkish Hazel click HERE
The male flowers are on yellow catkins that hang down ready to release pollen onto the wind. There may be over 200 unisexual male flowers on a single catkin.
Each maleflower is covered by a scale which lifts when the catkin is ready to release pollen. Underneath each scale there are 4 pairs of green stamens full of pollen. The stamens split open to release pollen for wind dispersal when the conditions are suitable.
The female flowers resemble a bud, with crimson stigmas that protrude when they are ready to receive pollen. The flower buds are located on the branch above the catkin, to avoid self-pollination.
The female flower bud is shown in close-up in this photo. Each bud has several flowers. Each flower has 4 stigmas to collect pollen. If fertilised, each flower will produce one nut, known as a cob.
Autumn Leaf Colours
Autumn leaf colours can be used to identify trees in Britain – some trees have leaves that turn yellow, others red and some stay green until they fall.The most striking thing about deciduous trees in autumn is not that they shed their leaves, it’s the fact that the leaves on some trees change their colour before they fall. Why does this happen – the leaves have been green all spring and summer? Why don’t the green leaves just drop off without changing colour and why on some trees do the leaves turn yellow and on others red. In fact most trees in Britain, for example Common Alder and Common Ash, shed green or brown leaves but about a third of all species turn either yellow or red.
In Britain our landscape consists of trees that originated in Europe, America, Asia and Australia. Most trees of European origin turn yellow with hardly any turning red. European tree species that turn yellow include the Norway Maple, Field Maple, Aspen, Silver Birch, Common Beech (yellow then brown), Common Hornbeam, Willows, Poplars and Limes. The Ginkgo introduced from China, has yellow autumn leaves. In America there are some native trees such as the Quaking Aspen, Tulip Tree, some Oaks, some Maples and some Hickories that are yellow in autumn but many more that turn red. Here are 8 examples of trees that turn yellow.
Not all conifers are evergreens. Some are deciduous and shed their leaves in autumn. Examples are the Swamp Cypress and the Dawn Redwood. For information on these trees click HERE
Nearly all the trees that turn red in autumn in Britain were introduced from North America or Asia. Examples are the Red Maple, Sugar Maple, Red Oak, Scarlet Oak, Pin Oak and Sweet Gum from North America and Japanese Maple varieties such as ‘Ozakasuki’, Sargent’s Cherry, Persian Ironwood, Snowy Mespil and Pillar Apple from Asia. A few European trees, such as the Wild Service Tree and the Bird Cherry turn orange/red and some, such as the Norway Maple and the Common Rowan, may turn orange/red under stressed conditions. Some varieties of European trees with red autumn leaves include the Sycamore ‘brilliantissimum’ and the Claret Ash ‘Raywood’. Here are 8 examples of trees that turn red in autumn.
Two main theories
A leaf is the main photosynthetic organ of a tree. This is a process in which carbon dioxide from the air is combined with water in the presence of light to produce sugars and oxygen. The molecule that carries this out is called chlorophyll. It absorbs red and blue wavelengths of light and reflects green so that the leaf appears green to us. It is a complex molecule with a ring of nitrogen at its centre surrounding an atom of magnesium. Shorter days and lower temperatures trigger leaf fall but this is a multi-step controlled shutdown process. Some trees just discard green leaves but in other trees the chlorophyll and proteins in the leaf are broken down and essential nutrients, such as nitrogen, are re-adsorbed and stored in the shoots and roots until spring.
As the chlorophyll breaks down, the leaf loses its green colour and other pigments can be seen. Carotenoids are yellow and orange and are already present. Anthocyanins, which give the leaf a red colour, are newly made. Carotenoids are needed to keep the cells going during the re-absorption stage so most trees that change colour have yellow leaves in autumn but 14% have red leaves. Why, then do some trees go to the expense of making Anthocyanins before the leaves fall? There are two main theories.
Anthocyanins protect the leaf from light damage during the period of re-absorption. This is the basis for the photoprotection hypothesis – it extends the leaf life during shut-down and enables it to send more nutrients back to the tree before the leaf drops. If this is true, trees with yellow leaves should drop their leaves earlier.
Alternatively the red coloration may be a signal to parasites, such as aphids, that have a strong preference for green leaves, to not lay their eggs on red leaves in autumn. This avoids future damage and is the basis for the co-evolution hypothesis. Red colour may be correlated with the level of herbivore defence in the tree, and therefore plants investing more in defences show more autumn colours. If insects adapt to avoid red leaves in autumn, this will lead to a co-evolutionary process in which both preference for green in aphids and intensity (or duration) of red in trees increase.
Flowers and Fruit in August
In August garden flowers are abundant with many coming into flower in late July or early August. Few wildflowers come out in August but grasslands are full of Knapweeds, Wild Carrot, Teasel, Scabious, Harebells, Ragwort, Thistles and Hawkweeds. Fruit is ripening on some trees and shrubs. Here are photos of 7 garden flowers and 3 fruits seen in early August.
This is a variety of Rudbekia fulgida. Rudbeckia may be annuals, biennials or perennials. They are native to North America. The common name is Black-eyed Susan
Japanese Anemone ‘Queen Charlotte’ . This hybrid was developed from the species Anemone hupehensis, native to China.
A Michaelmas Daisy hybrid. This is similar to the European wildflower Aster amellus named after the Archangel Michael, whose feast day is September 29.
The Globe Thistle flower heads, like all thistles, are made up entirely of disc florets. Native to Eurasia, it was introduced to Britain in the 16th century as a garden plant.
A Hibiscus hybrid based on the species Hibiscus syriacus which is native to China.
A Gladiolus variety. Gladioli originate mainly in South Africa, which has approximately 250 of the 300 known species.
Phlox ‘Mount Fuji’ is a popular garden plant. The Phlox family of 25 genera and 250 species is found mainly in North America with one genus Polemonium found in Europe and two in Asia.
Black Mulberry. The fruit turns red and is sweet and juicy at the end of July. This type of fruit is known as a multiple fruit because it consists of a number of drupes fused together to make one big fruit.
Bramble fruit, shown here, is black when ripe. Raspberry fruit is red when ripe. Where the fruit connects to its stem is the receptacle. It is fleshy and comes away when the Blackberry is picked but does not come away when the Raspberry is picked.
The fruit of the Elder is used to make wine and has many medicinal uses, but the seeds and other plant parts are toxic.