Ask Alys: your gardening questions answered

I have been using a liquid feed made from green alkanet (Pentaglottis sempervirens), which works well on all my vegetables. But I have been told that alkanet contains toxins that may adversely affect my health. What should I do?

You can eat green alkanet flowers, but I am not sure about the leaves: why anyone would try to eat something that hairy is beyond me. I've not heard that alkanet contains toxins, but those leaves are an irritant, as you'll know if you pull it up without gloves. I would stick to nettles and comfrey when making a liquid feed as they are both safe to use.

Green alkanet has very long taproots that are hard to kill; many consider it a pernicious weed. Making a fertiliser out of it is one way to tackle it. Those deep roots mean that it's a mineral accumulator, pulling up nutrients that other plants can't reach. It's always better to be safe, so continue to rot it down – the compost heap won't kill the roots – then put the weed soup on the heap to keep it moist. That way, you will get all the good stuff back into your garden while ridding it of a potential weed.