Chemicals in the garden – they have always been there!

November 2016
I had the kids’ Wildlife Trust WATCH group here last weekend; we had a go at using native dye plants like Woad, Weld and Madder that I grow.

Interestingly a lot of dye plants are good nectar sources for insects when they flower. But Woad leaves have to be used in the plant's first year of growth and it doesn’t  flower until its second year. You don’t have to destroy it when you harvest the leaves, however, you can ‘cut and come again’ like lettuces and herbs, and still leave the root in the soil to flower next year and produce seed.

Queen Elizabeth the First used to make lots of journeys around her kingdom to be seen, but always specified that any areas where Woad was being processed should be well circumnavigated because of the terrible stink. Like tanneries, woad processing used large quantities of stale urine to provide the alkaline solution needed.

Woad was also fermented. It was a long, arduous and smelly process, but can be made easier these days with the use of modern chemistry. All this is a good lesson for children in the uses of chemistry and history that eluded me when I was at school. It is also great fun for the ‘euuguhh! factor’ – great fun showing them the lichens I had been soaking in urine for a year to try and extract the dye! (Unsuccessfully, but maybe it was the wrong species of lichen)

There is also a lesson here about chemicals produced naturally by plants – why do they do it? Often we think of plants with poisons and bitter flavours as having evolved those to stop animals eating them. But I also grow Mandrake and Henbane in my medieval herb garden, which of course are horrendously poisonous to us, but I have found the slugs absolutely love them! Now it may be that where they grow naturally, in the dry Mediterranean that they don’t suffer from slug damage as much as they suffer goat browsing. But there must be some slugs and snails there?

And that brings me to the vexed question of how to deal with our slugs and snails. I do use a combination of methods like beer traps – a jar sunk into the ground with the dregs of my evening beer poured into it, if I remember in time. And that works quite well. But Spring and Autumn, when it gets really wet here, that’s not enough (and forget copper rings or dry/sharp material – leaves flop over the copper rings to make a bridge for molluscs, and the dry material of course gets soaked)

So I do resort to slug pellets sometimes, around particular slug favourite plants. I do not use those with metaldehyde anymore, as those are said to be the most poisonous for hedgehogs etc. that may eat the poisoned slugs. I use the ‘New Advanced’ slug pellets based on iron, but recently someone told me they are not so good either.

We have just had reports of lots of dead shrews being found around the Prestatyn area. This obviously poses a threat to scavenging birds and other wildlife. So I am still conflicted about using mouse poison in my polytunnel as well as slug poison.

Anyone have any real science evidence on these issues?

If you do fear that inappropriate use of chemicals has affected wildlife you can go to this government website for help; http://www.hse.gov.uk/pesticides/topics/reducing-environmental-impact/wildlife.htm





The magic of indigo chemistry – woad-dyed material changing from yellow to blue before your very eyes as it reacts with the oxygen in the air.  © Jan Miller-Klein 2016 www.7wells.co.uk

<< Blog entry >>