Go forth and propagate

Patience is required, but you could slash your garden re-stocking bills by doing some propagating. Here's how to do it, writes FIONNUALA FALLON

MANY YEARS AGO, having hatched a rather grand plan to grow my very own dwarf evergreen hedge from scratch, I decided to grow some box (Buxus sempervirens) from semi-hardwood cuttings. Perhaps if I’d taken the time to find out how long these particular plants take to strike (the more technical term for forming roots), I might have understood that patience would be required. But as it was, six long months passed while I endlessly poked, prodded and examined the various pots before, at long last, I spotted the pale roots slowly pushed their way through the base.

By that point, having got in the habit of regularly and roundly berating the cuttings for their unwillingness to grow, I felt slightly shamefaced. But after that, I spent the rest of the day in a very pleased if slightly self-congratulatory frame of mind, having happily discovered for myself that there is something truly magical about propagating a new plant from a tiny cutting just a few centimetres long.

Oliver Schurmann, the garden designer and co-owner (along with wife Liat) of award-winning, Dublin-based, Mount Venus Nursery (mountvenusnursery.com), knows this better than most. Every year the couple propagate 30 to 40 per cent of their nursery stock through softwood, semi-hardwood and root cuttings, using a propagation bench they fashioned from discarded wooden pallets. Simply insulated with a layer of polystyrene covered with sand, it is heated with a basic, thermostat-controlled, soil-warming cable bought from Cork-based suppliers Fruithill Farm (fruithillfarm.com).

At this time of the year, the bench is filled with thousands of softwood cuttings taken from the nursery stock plants over the previous few weeks, including dozens of trays of stachys, thyme, parahebe, centaurea, vinca, anthemis and Salvia nemorosa ‘Caradonna’, as well as many of the nursery’s rare shrubby salvias.

“It’s still not too late to take softwood cuttings of many semi-evergreen shrubby plants,” Schurmann confirmed to me last week when I visited the nursery. “In fact, better to do it now than wait until the spring, when some of them may have died over the winter.”

As I watched, he chopped short lengths (five centimetres) of soft young growth away from a pink-flowering Salvia greggii ‘Stormy Pink’, avoiding any with open flowers and gently pinching out any remaining flower buds. Using a razor-sharp scissors, he then trimmed each cutting back again, cutting cleanly between leaf-nodes (the part of the plant where the leaves join the stem) and slicing off any lower leaves so that just a tiny length of cutting (two to three centimetres) remained.

Once prepared, the salvia cuttings were then planted into plug trays filled with a 2:1 mix of granite sand and compost (as well as the tiniest amount of slow-release fertiliser). Each tray was placed neatly on the heated bench (set at 20 degrees) and the bench was then carefully covered with a thick layer of transparent polythene supported by low hoops made from bullwire. And that was it – quite simple, really.

“Any gardener could do pretty much the same thing at home on a smaller scale, using heated propagating trays or even just a warm room. The most important thing is to keep the cuttings covered with clear plastic until they’ve rooted – something like a sealed Ziploc bag slipped over a pot will work perfectly well,” he explained.

The number of Mount Venus Nursery’s softwood cuttings to successfully root is surprisingly high. “We’d expect a 100 per cent strike rate, with obvious root development within two weeks,” Schurmann said. And what then? “Once the cuttings have rooted, we take off the covering, remove them from the heat and let them grow on in the polytunnel until next spring, keeping a careful eye out for diseases like botrytis, and watering as required. Come March, we’ll pot them on. By summer, we should have some very nice salvia plants ready for sale.”

Oliver added that along with propagating box from semi-hardwood cuttings, he also propagates many herbaceous perennials from root cuttings at this time of the year, carefully lifting stock plants of Japanese anemone, Siberian bugloss, Navelwort and the Bloody Cranesbill, neatly slicing off short sections of their roots where new, white growth is clearly visible, before planting them into a compost-filled tray.

Another excellent, Irish-owned small nursery that also propagates almost all of its own stock from cuttings is Bannow Bay Nursery in Co Wexford (bannowbaynursery.com), whose specialty is hardy woody shrubs. “At this time of the year, we concentrate on what I call winter evergreens, things like hebes, cotoneaster, eleagnus, the double gorse Ulex europaeus ‘Flore Pleno’, Escallonia macrantha, griselinia and many different pittosporums,” says owner Annette Breen. “We take short cuttings (just 7.5 centimetres long), dip the ends in a liquid rooting powder and stick them into plug trays. Then they go into mini-tunnels inside our polytunnels. Given the scale of our production, we don’t use heat, but for any home gardeners who like the idea of trying their hand at trying their hand at propagation, a gentle heat of 18-20 degrees would be advantageous.”

Unlike softwood cuttings, Irish gardeners should expect such winter evergreen cuttings to take longer to root. “Depending on the species, it takes anything from one to four months. We kept ours covered until the spring (including a layer of fleece in cold snaps), except for a few hours twice a week when we remove the plastic for ventilation and check for disease or watering requirements. We pot them on in late spring and again in August and then the following spring, they’d be ready to be planted. So a bit of patience is required.”

Ah yes, patience . . . that constant bane of all eager-to get-going gardeners. Perhaps now would be an appropriate moment to quote Margaret Thatcher. “I am extraordinarily patient,” she said, “provided I get my own way in the end.”

This weekend in the garden

Take cuttings (see main article)

Where soil is not waterlogged, continue to plant bare-root and container-grown shrubs, trees, hedging, fruit bushes

Plant tulip bulbs

Protect vulnerable plants from frost with garden fleece

Lift any tender plants (dahlias, tuberous begonias, cannas, gladioli), cut back, wash, and leave to dry in a cool but frost-free place

Finish weeding and lightly mulching/manuring shrub, flower and vegetable beds

Collect leaves to make leaf mould, or add to compost bin