The Valency Valley
Galls. People often ask me what the strange growths are, which look like fruits, growing on the leaves of trees. These are called galls. They are formed when a plant’s cells are hijacked by an intruder, e.g. an insect grub or an egg laying insect – often wasps. Chemicals are exuded into the cells which cause them to divide and mutate and the plant forms a tumour-like growth. Oak trees are particularly vulnerable to this and will produce ‘knopper’ and ‘marble’ galls amongst others.
We have been surveying butterflies along the Valency Valley once again this summer. This year has been a good year for butterflies, and we have recorded the rare pearl and small pearl-bordered fritillaries once more. There is a healthy population of the more widespread silver-washed fritillary which is probably the largest British species and can’t be missed despite its rapid flight.
Both here and on the cliffs I have noticed large numbers of the clouded yellow butterfly this year (dark yellow with black wing tips). This is a migrant summer species from southern Europe and as such numbers fluctuate from year to year. In its warm native countries this strong, fast flyer is a prolific breeder producing up to four broods a year. Occasionally there is a big influx into Britain when the European population has swollen in favourable conditions. Eggs are laid in great numbers on clover, lucerne and trefoils. Spring migrants will have time to breed in the UK producing a single brood in the autumn, but none can survive the cold damp November weather.
Ever since the flood, we have been keeping a watchful eye on the appearance of invasive plants along the valleys. We all know about Japanese knotweed, and this hasn’t emerged as a problem. What have turned up though, especially this summer, are large quantities of Himalayan balsam.
This garden escape has found its way into the Valency catchment, and has begun to spring up all over the place. It spreads prolifically and can soon take over an area, much like knotweed. It is a tall very fleshy stemmed plant that likes streamsides and damp grassland. It has a very ornate pink flower and the ability to fling its seed a great distance once the ripened seed pods explode – some of you may have seen this filmed on BBC Wildlife shows!
Because of this we have been pulling up the plant whenever we see it in the Valley before this occurs! I have seen whole fields of the stuff when out walking in other parts of the country, where it’s obviously not been managed, so would hate it to get out of control here.