Q Which plants are root cuttings suitable for?
A This propagation method is suitable for herbaceous plants, such as Primula denticulata, some peonies, oriental poppies, Welsh poppies (it’s barely possible to propagate good red doubles in any other way), romneyas, Japanese anemones, echinacea, anchusa, cynoglossum, acanthus, phlox and so on.
It’s also suitable for some trees and shrubs, such as poplar, some willows, catalpa, paulownia, lilac, blackberries, raspberries, robinia and roses. If the tree or shrub is grafted on to another rootstock, don’t bother, as you won’t get what you wanted.
Caption: Oriental poppies, such as Papaver orientale 'Castagnette', are easy to propagate from root cuttings
Q When is the best time to take root cuttings?
A The convention is that winter (November to February) is the best time to try taking root cuttings, as plants are dormant or quiescent and full of stored food. But other feel that damage in plants can only be repaired by growth, so it’s best done when the plants are beginning to grow again or are in active growth, especially at the root. This can be midwinter for several herbaceous plants.
Caption: Dig down to find suitable roots
Q How should root cuttings be taken?
A Search for roots around a plant without digging it up.
Detach some roots and put them in a labelled plastic bag. At this stage, it’s obvious which is the top and tail of the root. Like carrots, they get thinner the further they are from the tops, and secondary roots come out at an acute angle.
You need pieces 3-5cm long if they are pencil-thick, shorter if they’re thicker, and longer if they’re thinner. Cut them with a sharp blade (blunt blades bruise the root tissue and may cause rot).
Line up the cuttings on the work surface, all the same way up. Professionals make an acute cut for the bottom of the cutting, and a straight one for the top. However, this wastes root tissue and, if you are methodical, it’s unnecessary. If you get them mixed up and can’t tell which way up they’re meant to be, root them horizontally.
Put one cutting in a small pot, or one per module of a modular tray. Or lay them horizontally in a seed tray, and cover by burying them about half a centimetre deep in compost.
Use open, airy compost. Peat composts are OK if mixed with vermiculite/perlite or coarse sand. In general, this mixture will improve any compost.
Place the cuttings in a light, airy place that’s cool and frost-free. Use old-fashioned frames, places close to buildings, and greenhouses. Once wetted, the cuttings are unlikely to need watering until any shoots are growing strongly.
When shoots appear, consider potting up or potting on. However, bear in mind that sometimes the root cuttings will shoot before new, secondary, roots have appeared.
Caption: Put the cuttings in the compost the same way up as they were growing on the plant