Once established, comfrey plants can be harvested at least twice per year, and in ideal conditions up to five times.
Harvesting entails removing all growing stems and leaves, taking care not to disturb new growth emerging from the base of the plant.
When to harvest comfrey
Comfrey plants can be harvested when they are around 2½ feet (75cm) high, but can be left longer for additional growth, or to allow them to flower.
Since Bocking 14 will not set viable seed, you do not need to be concerned about letting some or all of your comfrey flower before harvesting.
Leaving them to flower will reduce the overall yield of your crop, but does have other benefits: flowering comfrey is a tremendous pollinator attractant, and an excellent source of food for bumblebees, so conside leaving some plants to flower.
We tend to harvest half of our plants just before flowering, and leave the other half to flower for the bees.
For mature plants the first cut (in the UK) may be as early as mid-late April depending on how the plants over-wintered, the condition of the plants in general, and how they were fed.
In ideal conditions you can continue to harvest your comfrey every 4-6 weeks throughout the growing season, provided its well-fed and healthy.
For newly-planted comfrey, the longer you can allow the plant to grow without flowering and without cutting the better it will establish. Either remove flowering stems and only cut stems that are dying back, or cut once in mid-June to prevent flowering and leave plants alone for the rest of the year.
All comfrey should be cut in autumn, no later than mid-September. Feed well after this cut, giving your plants the ideal opportunity to build reserves before winter and emerge rapidly the folllowing spring. Any growth after this date should be left to wither in-situ – it will provide additional feed for the plant.
How to harvest comfrey
Use secateurs or hand shears to cut stems close to the base of the plant – a height of about 2 inches above the soil level is usually safe, making sure you do not damage new shoots. If you are careful you can also leave any young stems that may be up to 6 inches long – these will come away quickly after harvest.
We recommend wearing gloves when handling comfrey – the leaves and stems are covered with tiny, stiff hairs that can irritate the skin.
Once you’ve harvested your bundles of comfrey stem and leaf, check out our guide to the uses of comfrey.