MY column a couple of weeks ago about climbers and the damage they can do reminded readers of some other pestilential plants.
One of them is Himalayan balsam (Impatiens glandulifera), a relative of the ornamental Busy Lizzie, but on a grand scale. It can be up to 6ft tall and in bloom it is very pretty.
It was introduced here from India in the early 19th century at the same time as giant hogweed and Japanese knotweed, both of which I plan to write about some time. All were promoted for their ‘herculean proportions’ and ‘splendid invasiveness’. Himalayan balsam is now so widespread, particularly along river banks, that it is a considered a pest. Unlike many invasive plants it is an annual and is shallow-rooted, so it’s easy to pull up, but it has a brilliant seed distribution mechanism. When the pods are ripe they explode at the slightest touch:
Here it is in slow motion:
The ‘impatiens’ part of its Latin name means ‘impatient’ and you can see why.
The problem is that it grows so densely that it crowds out other plants, and being an annual it dies in the winter leaving river banks bare, not supported by a network of roots, and exposed to erosion through flooding. It is encouraged by a process called eutrophication, in which a body of water is enriched with minerals and nutrients from sources such as sewage, industrial wastewater and farming fertilisers. This process also causes algae to grow excessively. So one way to control it would be to reduce pollution.
I have to admit a small part in the spread of Himalayan balsam. When our children were small we lived in Bromley, Kent, and I ran the plant stall at the primary school fairs. One summer I found a large and rather beautiful plant in the garden, and when the seed pods developed I discovered for myself their explosive qualities. The children and I had a lot of fun popping them all. The result in the spring was masses of vigorous seedlings. I had the bright idea of potting some up for the plant stall, and they sold well. It was years later that I realised what I had done. Still, as I say, they do pull up easily so maybe Bromley has not quite disappeared under Himalayan balsam yet.
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On the topic of creepers, I saw these beautiful autumn tones this week:
The red leaves are Virginia creeper (Parthenocissus quinquefolia) and I believe the yellow leaves are the climbing hydrangea, Hydrangea petiolaris.
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In a column in August I showed this picture of beautiful ripening pears in a garden in our village:
This is the same scene this week:
I read the other day that in Britain 170million portions of fruit are thrown away every year. We are fortunate indeed if we don’t need to pick the fruit from our own gardens, even if only to give it away.