Llanelli Naturalists Newsletter - No. 74 - July 2008
Ian Morgan
Wintertime is when many of us plant trees and shrubs in readiness for growth in the Spring. The choice of both native shrubs (or cultivated varieties for your garden), is extensive but in this short note I shall focus on three, one of which is likely to pose an increasing threat to woodland biodiversity.
In line with the spirit of the title, I shall start with alder buckthorn Frangula alnus, a native shrub of damp woodland edges and sometimes in hedgerows that is rather scarce and scattered in Carmarthenshire. Alder buckthorn is rather an innocuous species, without any spectacular feature, but the small glossy leaves (that turn yellow in late autumn) and the greyish speckled bark catches my eye; it grows to about 10 ft when mature and is of clear value for wildlife. A nice planted example can be seen near the Visitors Centre at Llyn Llech Owain Country Park and there are others in the nearby willow carr, as well as at WWT Penclacwydd. When I worked for NCC/CCW, I encouraged the planting of this well-behaved shrub (not to be confused with the invasive sea buckthorn) as part of landscaping schemes or mitigation measures, particularly on the Coalfield of SE Carmarthenshire. The main reason was that this is the food-plant of the brimstone butterfly which is also scarce due to the scarcity of the caterpillars` host plant. To my mind, the brimstone butterfly is the sign of Spring`s arrival, perhaps even more than the singing chiff chaff or the first swallow, when the all-yellow males or the off-white females, fly on those sunny but fresh and fine March days (sometimes even earlier). In recent years, an increase in the number of brimstones has been witnessed in the Llanelli area where the earlier plantings of alder buckthorn are now maturing. I have even had brimstones breeding on those planted in front of my house at Pwll. Perhaps readers may wish to consider planting some, to encourage your own local brimstones, as they are easily grown from squashed berries placed in compost trays in autumn? Remember though, to wash your hands, as the berries have strong purgative/laxative effects!
The next shrub is our `baddy` – cherry laurel Prunus laurocerasus – which hails from the Canary Islands. Here, paradoxically, the evergreen forests where it grows are threatened. In Carmarthenshire however, it may be an oncoming threat to our native woodlands. In recent years, I have noticed an increase in the fruiting and subsequent seeding of this undeniably handsome, glossy-leaved evergreen cherry. It has been known to be naturalised in Stradey Woods since at least 1945, and it is seeding profusely in and –more worringly- around the arboretum at Gelli Aur, where control measures are ongoing. Part of the problem is that blackbirds, thrushes and wandering flocks of starlings love the berries (as a late summer visit to Gelli Aur will show). It seems that this change has been due to climatic changes, with the warmer wetter summers and the milder winters of late mirroring conditions in its native country. The seeds are spread in birds` droppings, inoculating other woods in the Tywi Valley or elsewhere. It would be wise to recognise this threat and act accordingly by cutting out and herbicide-treating incipient colonies.
The last shrub, whilst not native, falls into the `useful` category – garden privet Ligustrum ovalifolium. A very close relative, wild privet. L. vulgare is a true, if very localised native growing, for example, in cliff top scrub near Llansteffan and within clearings at Pembrey Forest. Both species are the food plant of Britain`s largest moth, the privet hawk-moth. This is an impressive moth (as is its caterpillar) and it never fails to impress children or other budding naturalists. The value of garden privet is that it allows this moth (and other localised species) to occur in urban areas, where the privet has been allowed to grow rather more luxuriantly around allotments or some gardens. Highly-manicured privet is less favoured. In recent years, garden privet has been neglected as a hedge choice, falling out of fashion and yielding to the troublesome `leylandii` conifers. Whilst not advocating the planting of garden privet in countryside situations, it may have a place in urban or urban edge landscaping schemes, thus allowing future generations to marvel at the magnificent privet hawk-moth. Its creamy flowers offer a bonus too – as a nectar source for many insects.
