Churchyard Nature Note with Andrew Tompsett

June 2014

ALIEN’ PLANTS TO AVOID

There has been a lot of publicity recently about the threat from plants introduced to Britain from abroad. Why the concern? Surely most of our garden plants are not native of this country and most present no problem? It is just that some non-native species, also known as neophytes, can become dominant when they escape into the countryside, out competing our own familiar flora and/or taking over open ground where rarer, less vigorous plants grow.

One of the most alien plants is the well known Japanese knotweed (pictured above) which was present in our churchyard but has now been eliminated – we hope! Japanese knot weed was brought to Britain in Victorian times as an attractive ornamental plant for large gardens. This is a very vigorous plant, growing at 2cm per day, and is perfectly hardy in this country. It has the capacity to smother other vegetation and can cause serious damage when the roots are beneath paving or tarmac which can be broken up when the growth starts in the spring. Unchecked dense stands are formed and the flowering is quite attractive although, thankfully, the seed is sterile in the UK.However, even small pieces of stem or root grow very easily and can be transported when soil is moved. This is devastating along watercourses which can be easily blocked. Cornwall is not alone in undertaking serious control measures and landowners have a legal responsibility for control (this can be daunting where property changes hands).
Another neophyte, widespread in Cornwall, but whose flowers are enjoyed by many people, is the white-flowered Three-Cornered Garlic, named from the 3-ribbed stem, which is seen along roadsides and waste ground and which has become naturalised since about 1850. It is spreading throughout the churchyard and Elsewhere the cheerful orange Montbretia flowers in late summer, enjoying the Cornish climate even more than that in its native South Africa.Considerations of competition with roadside orchids and other native wild flowers spurred on the Cornwall Council’s control measures such as on the Hayle bypass.

Whilst we do not want to see our native flowers overwhelmed, extensive control of these alien flowers within the churchyard is not really practical so we shall continue to see a mixture of native and non-native plants here. Even just this week a bramble expert noted a plant of the Himalayan Giant blackberry in the churchyard, should we expect some good crops later in the year?