I have a question about comfrey tea on my vegetable garden. Is is a bad idea to use Foxglove and nettles as a foliar fertilizer tea?
Some back ground info: Following a recipe for "green tea" from Sepp Holtzer's Permaculture book, I started a batch of tea with nettles and what I thought was comfrey about 3 weeks ago in a bucket of water from my pond. I collected the plants from a newly acquired property and thought I had an abundance of comfrey. I have only seen pictures of comfrey and not use it before. After the flowers started to open this week it was easy to identify them as foxglove. I know this to be very poisonous if consumed. In Sepps book he talks about using other plants besides the comfrey and nettles as beneficial teas for many uses on plants. I believe the nettles have high amounts of nitrogen, and other minerals good for my veggies. I'm concerned about the digitalis in the foxglove being sprayed on my garden and have any negative effects. We don't want any heart attacks here. Maybe I should dump this 1st batch and try only nettles. Are there other plants that you would suggest for this technique? I have some root cuttings of comfrey planted but they are too young to harvest.
As a general rule, the chemical compounds unique in the "tea" are not taken up whole by the plant leaves. Hot peppers added to the compost tea may leave enough capsicum on the leaves to deter rabbits and other mammals from nibbling on them, but the capsicum is not taken up by the plant. What is taken up by leaves are fragments of molecules, things that are small enough to be transported through the cell walls of the plant. So while sprays of calcium can be beneficial to tomato plants, because calcium can be directly taken up by blossoms leaves and young fruit, the glycosides in digitalis are huge molecules that just won't fit through the cell wall. They will most likely be broken down by the fungal and bacterial cells that are living on the leaves.
That said, I would not go spraying digitalis tea today and harvest things for my salad tomorrow. Poisons may not wash off with a quick rinse, and it may take several days for them to decompose.