Welcome to a bulletin of what to look for and what is happening.  These are placed on the information boards each season and we retain key extracts in the relevant category of this website.  The following is an extract of the Winter 2023 Newsletter.  

Current Works

At this time of year there are typically a lot of acorns falling from the native oak trees on the Common. If you are unlucky, a falling acorn might give you a minor but sore conk on the head as it falls from an oak tree. You will likely also see the non-native grey squirrel busy collecting the acorns for food. But if you have time, slow down and pick a few acorns up. Take a closer look. A lot of them this year will appear misshapen. This is caused by non-native tiny wasp called the Knopper gall wasp (Andricus quercuscalicis). There are over 70 species of gall wasps in the UK. Some are native but the Knopper gall wasp is believed to have arrived in the 1970’s on introduced Turkey oak trees. You are very unlikely to ever see a Knopper gall wasp as they can easily fit on a pin head (see below right). And don’t worry they will not sting you!

The Knopper gall wasp is now widespread and endemic to the UK but tends to be found more around urban and stately areas where there are Turkey oaks. Both Richmond Park and Petersham Common have removed all the Turkey oaks over the years to make room for our native common oak trees. The Knopper gall wasp will happily use our native common oak acorns as part of its complex lifecycle, and this is what causes the acorns to distort in what is called a gall. A gall is caused by a chemically induced growth change in the acorn caused by gall wasps. The acorn becomes a host for a future gall wasp grub. The Knopper wasp will hatch in the spring from the common oak acorn on the forest floor. Interestingly, all the Knopper grubs that hatch in the spring from the common oak will be female. The newly hatched female Knopper gall wasps seek out a Turkey oak to lay eggs on catkins creating catkin galls which hatch both male and female wasps in a short period. This completes the life cycle as the females from the catkins lay eggs on the common oak acorns in the early summer starting the cycle over. Some years there will be a surge of galls and a limited number of viable acorns such as this year. The Knopper gall wasp suffers catastrophic collapse in populations on regular intervals and then, there will be lots of viable acorns.

The Forestry Commission sees no impact on native oak trees and viable natural regeneration of the native common oak from gall wasps.Works to improve native songbird habitat will begin in earnest in the Autumn.

We will be coppicing some of the 50,000 native trees planted to encourage denser thickets for songbird habitat. Coppicing (cutting the trees to the ground) encourages thicker regrowth that forms a dense scrub layer that are ideal habitat for our native songbirds. We will also lay some of the planted trees to form hedgerows in a traditional style along Star and Garter Hill (road). This will also benefit birds, mammals, and many invertebrates. We will continue with path improvements and drainage works to reduce the impacts of erosion.