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Pontifications on Poison

Being some ramblings on events associated with poisonous plants.

Tuesday 28th June 2011

Isn’t nature wonderful? Last week, I mentioned that my Verbascum x hybrida ‘Southern Charm’ had blown over in the wind. This was before the full flower spike had opened. Like many other plants, the flowers on the Southern Charm open from the bottom of the spike upwards. I regretted that I hadn’t got around to staking the plants as the flowers are amongst my favourites.

Verbascum 'Southern Charm'

But, just a week later, as the picture shows, the top third of the flower spike has turned itself back to the vertical and looks stunning. I say ‘like many other plants’ but, it appears that this is not common to the whole Verbascum genus because the flowers on the two olympicums that have seeded themselves in the front garden seem to be opening at random on the spike.

It’s another example of a plant getting on and doing its job which is to flower, get itself pollinated and reproduce. The pull to reach up to the light as part of this process is amazingly strong. I remember seeing a tree, a few years ago when I was out walking, that had, at some early point in its life been blown over. It efforts to grow straight had been frustrated by some large rocks just next to it and, as result, the trunk had completed a full circle before finding itself in a position to grow straight and tall. I should try and find it and get some pictures.

But the best example of how keen plants are to reproduce was in the Poison Garden at Alnwick in the first full year. The layout of the Poison Garden included a number of steel cages. The purpose of these was something like five parts architectural, five parts for the PR value of saying that the garden had plants that were so dangerous they had to  kept caged, and one part because visitor contact with the particular plants needed to be avoided.

That lower priority on function meant that no consideration was given to the needs of the plants to be grown in the cages. The cages were heavy steel frames with mesh sides and no means of access to undertake any work on the plant within. Plus, the cages were of a uniform 2m height regardless of the growing habit of the plants.

Heracleum mantegazzianum, giant hogweed

In the second year of the Poison Garden, 2006, the gardeners planted three Heracleum mantegazzianum, giant hogweed, close together, and covered them with a cage. Now, even professional gardeners cannot be expected to know how to grow a plant like giant hogweed so the Alnwick Garden staff can be forgiven for not realising that all three plants would flourish and that, within a couple of months of planting they would completely fill the cage.

In fact, by June, as the picture shows, the flowers of the plants were pressing so hard against the cage that visitors were genuinely concerned that they might be about to burst through and fire toxic material all around. So, it was decided to remove the flower heads. Because of the nature of the plant and the design of the cage, that relatively simple task required six gardeners in full protective clothing and facemasks so that no skin was exposed.

The idea was for four people to lift the cage up enabling the other two to remove the flower heads. Unfortunately, the three plants growing so close together were exerting outward pressure on each other so that, when the cage was removed, all three splayed outwards. It was immediately obvious that it would be impossible to stand the plants up and replace the cage so the plants were cut off about a metre from the ground and the cage put back in position.

Heracleum mantegazzianum, giant hogweed

Within a month new flower heads had formed on the plants without reproducing the tall stalks normally associated. To the right of the picture of this second flowering you can see the cut off stalk from the first growth. Though much smaller and showing no tendency to burst out of the cage, it was decided to remove these flower heads to prevent them seeding. This was a much simpler operation though still requiring quite a bit of muscle to tilt the cage to allow access.

Remarkably, within three weeks the plants had again flowered, this time on stalks that were no more than 25cm in height.

Talking of flowering, my poppies are just beginning to show off their wonderful colours. The very definition of a ‘Lethal Lovely’.