Transplant seedlings 2-3′ apart in rows 3′ apart. Keep the bed well-watered until plants are established. Comfrey should not be harvested in its first season as it needs to become established. Any flowering stems should be removed during its first year as these will weaken the plant. Comfrey plants can produce 4-5 pounds of leaves per cutting during the growing season. Six plants is enough for most gardeners, which means allowing a planting space of about 6 by 10 feet or 3 by 20 feet for your comfrey bed.
Comfrey can be difficult to remove, once established, as it is deep rooted and any roots left in the ground will sprout new growth. If you are concerned about comfrey taking over your garden, it can be grown successfully in large containers or garbage cans. Be sure to drill drainage holes in the bottom of each container, fill with a soil and compost mix, and plant.
Comfrey symphytum officinale
Comfrey, a member of the borage family (also spelled Comphrey), is a strong-growing perennial with large, hairy broad leaves that grow 12-18″ long. Comfrey is used as a fertilizer and as an herbal medicine. An excellent source of potassium (needed for flower, seed and fruit production), its leaves contain 2-3 times more potassium than farmyard manure and is a valuable source of fertility to the organic gardener. It is advisable to wear gloves when handling comfrey as the leaves and stems are covered in hairs that can irritate the skin.
*Warning: Comfrey should be restricted to topical, external use only, and should never be ingested, as it contains dangerous amounts of hepatotoxic pyrrolizidine alkaloids (PAs). Do not apply to broken or abraded skin. Do not use when nursing.
Comfrey can be used to help activate compost, as a liquid fertilizer, and as a mulch or side dressing.
Compost activator – if you have lots of dry brown material and the pile is slow to heat up, just layer the fresh comfrey leaves and stems in as you add other material to your pile. Do not add large quantities of comfrey as it will quickly break down into a dark sludgy liquid. It needs to be balanced with more fibrous, carbon-rich material.
Liquid fertilizer – place leaves in the bottom of a large bucket add water or allow rainwater to fill for 4-5 weeks. This will produce a ‘comfrey tea’ which can be used whenever you water your plants. Comfrey tea has a bad odor, so brew it away from sensitive noses. The tea may be used full strength or diluted to about half strength—to the color of weak tea. Another method is to stack dry leaves under a brick or other weight in a large bucket that has a hole drilled in the base. When the leaves decompose a thick, black comfrey concentrate can be collected. Be sure to place another container under this bucket to catch the concentrated liquid. This liquid must be diluted at 15:1 before using.
Mulch or side dressing – use a 2″ layer of leaves (not stems, as these can root) around garden plants or trees. The leaves will slowly decompose and release nutrients directly into the soil. Useful for crops that require extra potassium.
The second year you can harvest leaves when the plant is about about 2 feet tall or starts to form flower stalks. Cut off the whole plant about 2 inches above the ground with pruners or a sickle. Be sure to wear gloves and long sleeves when harvesting comfrey, as it can irritate your skin. After harvesting, give your comfrey a good watering and renew the mulch layer. The best time to cut comfrey is shortly before flowering. This is when the nutrient value is the highest. While Comfrey will continue growing into mid-autumn, it is not advisable to continue taking cuttings after early autumn in order to allow the plants to build up winter reserves. Depending on your climate, you may be able to harvest four or more times per a year.