Horsetail

 This strange plant is the Dutch rush Equisetum hyemale which isn't a rush at all - it's a member of that strange division of the plant kingdom known as horsetails. We found it yesterday, growing in a ditch beside the disused railway line that now forms the Derwent Walk Country Park in Gateshead.

To some these flowerless stems must seem like the dullest plants on the planet but they are living fossils, descendants of giant ancestors that once formed a major component of the flora in the Carboniferous swamps, 300 million years ago. The Dutch rushes that we found yesterday grew to about 60 cm. tall but their ancestors grew to tree-sized proportions, some 30 metres tall, and are commonly found as fossils in coal measures. At that time the amphibians were the dominant form of land vertebrate life.



Compression fossils of horsetail stems, like these that we found on the beach at Dawdon on the Durham coast, are easily identifiable as they show the same pattern of grooves and ridges found in present-day horsetails. These stems were about ten times greater in diameter than the Dutch rush stems in the picture above, so if you were to scale up its height in direct proportion this particular fossil ancestor might have been roughly the height of a double-decker bus when it was alive.

This is the distinctive cone of Dutch rush, with that little spike at the top. When it's ripe in spring .....

.... each of those hexagonal sections will separate and elongate on a short stalk, .... like .....

...... these, which belong to the common field horsetail Equisetum arvense. The spores that are released from those yellow sporangia under the hexagons are unique to horsetails ....




.... because each has four long arms called elaters which are curled around the spore during development but are deployed when it dries out and is released, increasing the aerial buoyancy of the wind-dispersed spore.

Nuthatches

When we first moved to Durham, nearly 40 years ago, nuthatches were not very common birds here. I can still remember the first one that I spotted, hammering away at a yew seed wedged into the fissures in the tree near Prebends bridge in Durham city.

Since then they have become very common birds throughout the county and it would be an exceptional day out if we didn't see or hear at least one. I saw these two within ten minutes of each other in Auckland Park, Bishop Auckland, last week - and heard two more there. 

They are now frequent bird table visitors in winter too, and in spring their noisy courtship is a conspicuous feature of woodlands. Their numbers seem to have increased most noticeably in the last decade - although I'd have to concede that maybe I'm also becoming more aware of them.

Which begs the question "why have their numbers increased?". It can't be food supply because their staple food - tree seeds - can't have changed much. Climate change - the favourite driver for everything these days - seems unlikely too as these are hardy little birds. I can't imagine that there has been any decline in any particular predator either.  Maybe bird table feeding has had some effect, but that can't be the only reason as I see them as often in remote places as I do around habitation. 

It's all a bit of a mystery, but it's a delight to watch them feeding at this time of year, when there's a massive abundance of food for them to choose from.

The sweet chestnut that refuses to die....

Auckland park, in Bishop Auckland, has an interesting collection of old trees and these venerable sweet chestnuts are amongst the finest.

Some, like this one, are in the prime of life and produced a very heavy crop of chestnuts this year. 

There are four mature trees that were planted in a line beside a small stream. The ground under them is covered in a thick layer of their serrated leaves, spiny fruit husks and nuts that will keep the squirrels well fed for weeks to come.

The low-angle late autumn sunshine this morning showed off their fissured bark beautifully. 

One of the four has been dying for the thirty five years that I've known it. It has shed most of its branches, much of its bark, has been attacked by wood boring beetles and fungi .....

... and yet every year it sprouts new growth, refusing to die. There could be decades of life left in it yet, unless the roots finally rot and it's blown over by a gale and ......

...........that would be a pity, because I'd really miss this gnarled old trunk. It's one of the park's characters.