But it turns out that comfrey is a little powerhouse of a plant. It can be used for medicinal purposes because it contains allantoin, which stimulates cell growth and repair, and as a high-protein animal feed, but that’s not why I’ve got my eye on it.
Nope, I’m interested in it because it’s a great fertilizer. Comfrey is high in potash, aka potassium (the “K” in NPK fertilizer ratios), which means it’s an excellent feed for overall plant health and particularly good for tomatoes and flowers later in the season. One source says that comfrey has more than twice as much potassium as farm manure and 30% more than compost. The NPK (nitrogen-phosporous-potassium) breakdown of comfrey leaves is 1.80-0.50-5.30 for true comfrey and that last number bumps up to 7.09 for Russian comfrey. On “Gardener’s World,” good ol’ Monty Don made comfrey tea and then watered his plants with it. He also used it as a foliar feed. And he used a big bunch of leaves as mulch for his tomatoes. Just slapped them right on there. They will feed the soil as they decompose. And anything that was left, including the stems, was thrown in the compost pile where it kick starts a pile that’s a little heavy on browns (i.e. carbon-based material). And another source claims that earthworm farms have found that adding comfrey to their worm beds increases worm numbers by 400%. Even if that’s an exaggeration, imagine what it could do for the worms in my compost bin.
You can also put a few leaves near plants prone to slug damage. Apparently it is so tasty to slugs that they will forego eating anything else in favor of attacking the comfrey. I’m not sure howI feel about that logic as it’s a little bit like feeding the deer in your yard and expecting them not to eat your garden, but it might be interesting to try.
I ordered Russian comfrey (Symphytum x uplandicum), a variety called Bocking 14, which is said to be sterile, so at least I don’t have to worry about it reseeding all over the place, although cutting off the flowers before they set seed would also work (this is so much easier said than done). Apparently it is best to use it before it flowers, or right as it starts flowering. This strain is not great for animal feed—apparently it is more bitter than other strains—so I’m hoping that it won’t be tasty to deer.
I’m going to find a little patch that’s out of the way. I’m still worried about it getting aggressive, but I think if I can provide it a nice little spot away from the main garden areas, I can let it be true to its nature.
Growing my own fertilizer: what could be better? I’m becoming a more self-reliant gardener, recycling in my own yard and saving money in the process.
Comfrey, here I come.