Get close to comfrey - nature's natural mineral mine

Comfrey, a favourite herb throughout history, is a great natural fertiliser, writes FIONNUALA FALLON

IT GOES BY many names including bruisewort, knotbone, Saracen’s root and Russian’s Prayer, but most gardeners know it as comfrey – the herb whose leaves are such a remarkable, near-magical source of nitrogen, phosphorus and especially potassium that when used as a green manure, it’s the equal of farmyard manure or garden compost.

Mentioned throughout history by historians, herbalists and naturalists such as Herodotus, Dioscorides, Pliny and Culpeper, the herb’s usefulness is such that it inspired a 19th-century, Essex-based Quaker smallholder by the name of Henry Doubleday to import the plant all the way from Russia. His research on comfrey then served as an inspiration to the founder of the modern organic gardening movement, Lawrence Hills, giving us the Henry Doubleday Research Association – now known simply as Garden Organic (gardenorganic.org.uk).

Lawrence Hills spent much of his life researching the potent powers of the herb he subsequently described as "a natural mineral mine", not only writing a book on it ( Comfrey: Past, Present and Future) but also carefully cultivating and investigating the different species and cultivars in order to identify those most useful. The result is the plant that organic gardeners know as Symphytum x uplandicum 'Bocking 14'– the sterile comfrey cultivar that Hills described as the best all-round variety for gardeners and which is named after the HDRA's first, one-acre headquarters at Bocking, near Essex.

It’s a clone of this very same plant – a living piece of gardening history – that OPW gardeners Meeda Downey, Brian Quinn and Paul Whyte have been busily planting in the walled Victorian kitchen garden over the past week.

“The plants came from the garden of Dr McCullen , who lives nearby,” explains Brian. “We lifted and divided them before transplanting them about 60cm apart into one of the side panels in the walled garden – it seems comfrey prefers to be lifted now or in the autumn, rather than in winter.

“It’s naturally very, very vigorous, even invasive, so I expect the plants to be just fine. All they might need is a little watering to begin with, and then we’ll keep them weed-free. We won’t be harvesting any leaves until next year, when the plants are properly established.”

Fellow OPW gardener Paul Whyte also thinks the plants should do well in their new location. “Comfrey likes a very rich, dampish, slightly shady spot so we’re growing it against the east wall of the garden, where the soil is less likely to dry out. I’d say the plants should thrive. The only thing that surprised me was how brittle the long tap-roots are. We had to be careful not to accidentally break them while we were lifting them.”

But while the OPW gardeners won’t be able to use their comfrey plants as a fertiliser until at least next spring, many gardeners with well-established comfrey patches can start harvesting the leaves around now. Comfrey is an especially suitable plant food for potash-hungry crops such as potatoes, tomatoes and gooseberries and so this month – as seed-potatoes are beginning to be planted – is an ideal time to use it as a green manure.

In his book Grow Your Own Fruit and Vegetables, Lawrence Hills recommended spreading a thick mulch of the wilted leaves (cut them the day before) along the bottom of the potato trenches before covering them with a thin layer of soil and then setting out your seed potatoes. "The cut comfrey appears to heat like a long and narrow 'compost heap': the potatoes get away fast, using the supply of balanced foods directly where these are needed, and when they are dug, there will be only a little powdery humus remaining," he wrote enthusiastically of the herb.

If you’re growing a variety of comfrey other than the early-leafing ‘Bocking 14’, you may find that you don’t yet have enough foliage to do this. In this case, Hills suggests waiting until later in the spring to use the leaves as a light mulch, where it will act both as a feed and a weed-suppressant while also protecting the emerging foliage of “earlies” from late frosts. He also points out that the comfrey trench method as used for potatoes is also suitable for later crops such as runner beans, French beans or late peas. Finally, a liquid manure can also be made of the leaves – a large barrel or rubbish bin with a 1cm hole drilled in the bottom is all that you need. Fill with comfrey leaves, weigh them down with a wooden board covered with a few rocks or bricks, cover with a lid, and then place a bowl underneath the hole to collect the smelly, sticky black fluid as it appears. This can then be stored in sealed jam jars and used during the year as a liquid plant feed (dilute with water at a ratio of 10-20 water: 1 of comfrey solution). Tomato plants, in particular, love it.

Elsewhere in the walled garden, the OPW gardeners have been hard at work planting seed potatoes (varieties Sarpo Mira, Colleen, Orla, Records and Arran Victory) as well as carrot seed (varieties Ulyses, Major and Artemis) , and parsnip seed (White Gem and Javelin).

“The dry weather has been great,” explains Meeda. “We’ve got the parsnip and carrot seed sown already and if it stays like this, we should – fingers crossed – have all the potatoes planted within a few days. We’re filling two large panels in the walled garden, planting into broad ridges so that they have plenty of space to grow – the plan is to avoid having to earth the plants up later on. Once they’re planted, then it’s off to the glasshouses later this week to start sowing seed of more tender flower and vegetable varieties.”

Courtesy of potato-collector David Langford and gardener Dermot Carey, Brian and Meeda also took delivery this week of a dozen rare heritage potato varieties, including Irish Apple (a variety which dates from the late 1700s), Peach Blood and Mr Little’s Yetholm Gypsy.

“The plan is to grow the seed potatoes on in pots for the moment, just to bulk up the numbers, and to then sow them in the walled garden next spring,” explains Brian. “It’ll be very interesting to see how they do.”

Centuries-old potato varieties and a potent, powerful herb with a history that stretches back beyond the medieval crusaders to the ancient Greeks and Romans: all, it seems, are part of a normal day in the life of the hard-working OPW gardeners.

** The OPW’s Victorian walled kitchen garden is in the grounds of the Phoenix Park Visitor Centre, beside the Phoenix Park Café and Ashtown Castle. The gardens are open daily from 10am to 4.00pm

** Next week Urban Farmer covers sowing seed in the OPW glasshouse.

** Fionnuala Fallon is a garden designer and writer

WHAT TO: sow, plant and do now

Sow(in a heated propagator, to plant out later into a greenhouse, tunnel or outside): Aubergines (Bonica is best), alpine strawberries, French beans for cropping in pots inside (choose a disease resistant variety suitable for early sowing), asparagus, celery, celeriac, tomatoes, chillis, and peppers, physalis (Cape gooseberries). Also sow single tender flowers like French marigolds, tagetes etc. to attract beneficial insects which help with both pests pollination.

Sow(in modules under cover without heat, covering with fleece on frosty nights, for later planting in the tunnel or outside): beetroot, broad beans, mangetout and early peas, late spring and summer cabbages, red cabbage, early Brussels sprouts, cauliflowers, calabrese and summer sprouting broccolis, carrots(direct in soil for early tunnel crop), onions and leeks, spring onions, lettuces, kohl rabi, Ragged Jack and Cavolo Nero kale for baby leaves, radishes, Swiss chard, summer spinach, white turnips, salad mixes, and soft herbs like parsley, dill, fennel, greek oregano and coriander. Where youre not planting crops until May, its also worth sowing quick growing soft green manures like red clover, lupins, fenugreek, mustard and phacelia to help improve the soil and feed the worms - make sure varieties fit into your rotation pattern as far as possible.

(Sowing details courtesy of Nicky Kyle, nickykylegardening.com)

Plant outdoors:Seed potatoes (first earlies), onion sets, shallots

Do: Finish ordering seeds, hoe young weeds where soil is workable outdoors. Chit potatoes - and plant chitted early varieties in 2-litre pots in or direct into greenhouse bed for an early crop (planting to crop about 10 weeks) Don't plant in soil where youre going to grow tomatoes later - better to grow in pots, which an be moved outside later as space gets tight,