GBFD: March 2015

Christina at My Hesperides Garden hosts Garden Bloggers Foliage Day each month. I missed it yesterday, but better late than never:

daff buds

My snowdrops and crocus finished their show a week or two ago, but the daffodils will take their place very soon. We bought our house at the end of March, many years ago, and I remember the day we closed on the house we drove by, and the front garden was full of waving yellow blossoms.

nettles and comfrey

Stinging nettles (Urtica dioica) and comfrey (Symphytum officinale) grow in a half-barrel in my garden, providing an enduring source of fertilizer.

The fertilizer barrel woke up last week as well. For two years now, I’ve grown stinging nettles (Urtica dioica) and comfrey (Symphytum officinale) in a half whiskey barrel to produce homegrown liquid fertilizer. Concocting this homebrew is not for the weak of stomach: It reeks. But the nettles provide a terrific source of nitrogen, and the comfrey provides nitrogen, potassium, calcium and phosphorus, which helps promote root growth and blooming/fruiting. My garden plants love it, and the tea feeds the soil.

Red stems and budding green leaves of Salix 'Hakura-Nishiki.'

Red stems and budding green leaves of Salix ‘Hakura-Nishiki.’

And my willows are leafing out. I’m new to growing willows but love the fact that I can whack them back in early spring and they’ll produce lots of lush growth each year. I’m not whacking them this year; I only planted them last fall, so I plan to give them a season to get settled in. I have, however, cut a few twigs to make willow water, which promotes rooting in cuttings. I’ll talk about that in a separate post.

I hope you northern-hemisphere types are enjoying spring wherever you are.

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Comfrey: A plant’s smelly, magical wonder food.

Using commercial fertilizers, particularly sustainable or non-synthetic ones, can get really expensive. Compost and manures add important organic matter to the soil, which helps to build the subterranean ecosystems that support plant health, but they don’t add much in the way of major nutrients.

Fortunately, nature has provided a means to make our own sustainable fertilizers. Comfrey (Symphytum officianale), a plant that grows well in most gardens, provides nutrient boosts when added to compost or used in liquid fertilizers. And once you’ve bought the plants, it’s free.

Comfrey plants (Symphytum officinale) photo by Trish Steel [CC-BY-SA-2.0 (http://creativecommons.org/licenses/by-sa/2.0)%5D, via Wikimedia Commons

Comfrey is a borage relative. Hardy to Zone 3, it has large, broad leaves like those of Pulmonarias, to which they are related, and small clusters of blue or white pendulous flowers. Comfrey’s fuzzy, sometimes prickly leaves discourage insect pests. It grows in a range of soils in sun to part shade, and uses its impressive root system, which may grow anywhere from 6 to 10 feet deep, to mine minerals from the subsoil, aerate its surrounding soil and break up the heaviest clays. It will regrow from tiny slivers of root, though, so be sure to plant it where you want it. If you are as indecisive as I am, grow it in a container. You won’t get quite the same level of benefits as compared to comfrey grown in the ground, but at least you won’t have it permanently installed.

Comfrey has been used in the past as an herbal medicine, but research proves comfrey contains poisonous chemicals called pyrrolizidine alkaloids (PAs). The roots contain up to 10 times the amount of PAs than the leaves. Its toxic chemicals can be absorbed through the skin, though, so it is advisable to wear gloves when handling comfrey. Do not take comfrey internally, as it is extremely toxic to the liver and may also be carcinogenic.

Comfrey (at right, with large leaves) and stinging nettle (Urtica dioica, at left, with serrated leaves) grow together in a barrel in my garden.

Comfrey (at right, with large leaves) and stinging nettle (Urtica dioica, at left, with serrated leaves) grow together in a barrel in my garden.

For plants, though, it’s a wonder food.

Comfrey contains high levels of the macronutrients nitrogen (N), phosphorus (P), and potassium (K), as well as calcium and vitamin B12.  Comfrey also contains allantoin, a chemical compound that stimulates cell growth and regeneration. It may be the allantoin that makes comfrey so effective as a fertilizer. Extracts from comfrey’s leaves have antifungal properties, and have been shown to effectively combat powdery mildew.

It’s good to know the specific epithet of the plant you’re getting. Symphytum officianale, the species, will seed prolifically and may become problematic in the home garden. The Bocking 14 strain of comfrey (Symphytum x uplandicum) contains the high nutrient levels of the species, but it’s also sterile, so it won’t self-seed and become invasive. Bocking 14 is difficult to track down in the United States, but is available from a few Internet sources.

Comfrey leaves can be used as a mulch or buried in the garden bed at planting time. As they rot down, they’ll enrich the soil. Take care when using them as a mulch, though: The decaying leaves can be attractive to slugs, so don’t mulch with them around leafy greens or ornamentals like hostas.

A more versatile way to use comfrey is as a liquid fertilizer or tea. To make the tea:

  1. Chop up a handful of fresh leaves (use gloves), and place in a container with a well-fitting lid.
  2. Add water to cover, submerging the leaves with a rock if necessary.
  3. Let the mix rot down for 3-4 weeks. At this time, the comfrey will have been reduced to a stinky black goo.
  4. Dilute the comfrey liquid concentrate at a rate of approximately 1 part comfrey to 15 parts water. The final product should be light brown in color, like weak tea. Water it in around your plants that need a boost, particularly fruiting plants, or use the tea as a foliar spray on plants that are susceptible to mildew.
  5. You can seal up the rest of the concentrate for use at a later time, or bury it in the compost pile to supercharge your compost.

Comfrey tea is higher in phosphorus and potassium, so you may wish to blend it with nettle tea to get a better nitrogen boost. This tea will feed the soil as well as your plants, ultimately making your plants more resilient. For a gentle, natural fertilizer, comfrey is hard to beat.