What Gall?

For my birthday I was bought a great book about nature and flicking through it I found a fun craft instruction page that describes how to make a necklace out of oak apples.

Oak apples I thought… what on earth are they!

Well this sparked my interest and with a bit of pointing in the right direction from my mum and google I was able to find a whole load of information on these fascinating growths. And yesterday whilst looking on the ground at the early shoots of blue bells I found my first and actually knew what it was.

So here is a bit about them.

An oak apple is technically a gall, a growth on a plant that is induced by increased amounts of plant growth hormones stimulated when an insect lays its eggs into the plant tissue. This is so that the gall can feed and protect the gall-maker.
In the UK these galls are most often as a result of Gall wasps. They are a minor pest though and oak trees are not at threat because of them though they can substantially reduce the acorn crop in some years having consequences for the food chain such as squirrels and Jays.

There are different types of galls, I found an oak marble gall only a few weeks ago in my parents garden, a bird must have dropped it!
I am pretty sure that I have also seen a knopper gall last September and had no idea what it was but concluded what it was was killing the tree and disgusting, now I quite like it and will be taking it home if I see it again!

I will be on the lookout for these ones below, why don’t you try to find them too?
You could make it into a treasure hunt with the children and if you collect enough make a piece of jewellery/key chain.

The Oak apple galls are flattened rounded galls up to 4cm to develop on twigs in spring. The galls are spongy, brownish white with pink tinges.  Males and females emerge in midsummer and eggs are laid on oak roots. The next (asexual) generation produces marble-like galls on the roots, from which females emerge in late winter to start the cycle all over again.

Oak marble galls are hard woody spherical galls up to 2.5cm on the stems. Initially green they later turn brown and can persist for several years.

Oak apple

Oak artichoke galls are enlarged shoot tips caused when eggs are laid into buds and occur during the summer months. The next generation in spring develops small hairy pale green or brown galls on the male catkins.

Common spangle galls are tiny yellowish brown discs that form on the underside of oak leaves in late summer-early autumn. The galls drop to the ground in autumn and females emerge in spring to lay eggs on the male catkins. The next generation causes slightly larger spherical fleshy galls on the catkins. These galls are yellowish or reddish and are known as currant galls.

Smooth spangle galls are small, saucer-shaped, yellowish or pinkish discs without any hairs.  Forming mainly on the underside of the leaf each gall contains a single larva.  Pupation takes place during the winter while the galls are on the ground and females emerge in the spring.  They lay eggs which give rise to small, oval, green galls which are attached to the catkins.

Silk button galls are tiny golden brown discs with a pronounced central depression on the underside of oak leaves in late summer-early autumn. The next generation in spring forms small oval galls on the male catkins and leaf margins.

Oak cherry galls are spherical pithy galls up to 2cm on the underside of oak leaves in late summer-autumn. The galls are yellowish green or red and can remain attached to fallen leaves. The spring generation forms inconspicuous galls in oak buds.

Acorn or knopper galls are now widespread after becoming established in the UK during the 1970s. Eggs are laid during early summer in the developing acorns and the acorn is converted into a ridged woody structure in which the gall wasp larva develops. The gall is initially yellowish green and sticky but later comes greyish brown.

Knopper galls

Oak apples are so special that they even have had their own day, ‘Oak Apply Day’ or ‘Royal Oak Day’. This was a public holiday on 29th May to commemorate the restoration of the English monarchy in 1660. Whilst it was formally abolished in 1859 the date retains some significance in local or institutional customs.
I will have to put this date in my diary and if I have collected enough oak apples by then I will wear them as a necklace to commemorate the day.

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