At last a little leaf has confirmed that my “pigeon tree” in Cardiff’s Thompson’s Park is an oak. I delayed publishing this update until I had seen that sign, as I didn’t want to miss it – like your baby’s first steps!
When I previously visited on March 31 I thought the tree hadn’t changed at all in the last month. Although when I looked closer at the pictures I had taken in bright sunlight I realised I was wrong. Something was going on. The buds that were tight and closed and brown last month were now stretching and showing gold and light green colouration.
The tree has always seemed very dark and brooding, but now the weather is a bit drier and the sun is shining, it is perhaps lightening up.
From this direction the tree almost seemed to be covered in white blossom…
But on closer inspection it was a magnolia tree behind the oak…
I know my friend Paul Seligman has suggested in the past that I should do a post about all the plaques on Cardiff park benches. But I have always restrained myself, as I get weepy at memorials to loved ones who have passed away. I will make an exception here.
Sadly my searches online tell me only a little about Dr Kenis Barbara Gillard. Kenis is a name of Celtic origin and her maiden name was Flynn. I wonder if she was a medical doctor or a doctor in some other subject? In her will she left a bequest to the French and Religious Studies departments of Cardiff University and she seems to have been a supporter of the Cats Protection Society.
At least such plaques on park benches make us think for a moment about the people they commemorate.
But back to the tree. I could see something unusual up in the branches…
I naturally think of these galls as “oak apples”, and I have seen them on another small oak beside the river, but I did a bit of research and now I think these are “oak marbles”, created by a different insect than the bigger, lumpier “oak apples”. Apparently oaks suffer from many different sorts of gall.
The particular wasp responsible for marble galls (also known as bullet galls, oak nuts or Devonshire galls) is the tiny Andricus kollari.
The wasp has alternating sexual and asexual generations taking a year, or sometimes two years, to complete the cycle.
The adult female lays single eggs in the developing leaf buds of native British oaks in May or June. The larvae feed on the gall tissue resulting from their secretions. The spherical gall turns brown as it matures and a parthenogenetic winged female escapes through a tiny round hole in autumn, leaving the empty gall on the twig.
These females can lay fertile eggs without the help of a male and this is usually known as the asexual generation. But they don’t lay these eggs in common oaks. The turkey oak (Quercus cerris), introduced into Britain in 1735, is needed to complete the life cycle. Andricus kollari itself was introduced to Devon from the Middle East, home of the turkey oak, in the 1830s. I am assuming that wasn’t intentional.
The “asexual” females lay eggs in the leaf buds of the turkey oak, with small oval galls growing through the winter and becoming visible in early spring, looking like ant eggs or pupae between the leaf scales.
The emerging adult wasps are males and females, which fly to the common oaks – and mate, I assume – before the eggs are laid to create the marble galls and start the cycle over again.
The galls contain large amounts of tannic acid, used for making iron-gall ink and dyeing cloth. Traces of iron-gall ink have been found in the Dead Sea Scrolls and it has been used for thousands of years – but it isn’t very good. The ink fades and damages the paper.
According to Wikipedia: “Powdered galls mixed with hog’s lard and applied to the posterior were said to be good for curing piles.” Extract from the gall is also used in deodorants because tannic acid has anti-bacterial properties.
The existence of the galls perhaps suggests my tree is either an “English”, pedunculate oak (Quercus robur) or a “Welsh” sessile oak (Quercus petraea). The main difference is that the Pedunculate oak bears its acorns on stalks. We shall see, maybe.
And finally, an interesting cavity…
For the first time the grassy soil around the tree was dry enough to walk on, so I was able to get closer to the oak. This looks like a natural hole, not perfectly round like a woodpecker nest. But all the same, has some creature taken up residence in it?
See you next month…