If producing plants from bits of stick or pieces of stems sounds improbable, propagating from sections of root might seem even more unlikely. You only need to think of dandelions regenerating themselves from the smallest piece of root left in the ground, though, to realise that it one of Nature’s efficient ways of proliferating plants.
In theory root cuttings can be taken at any time of year but those taken during the winter seem to develop into sturdier plants.
Some plants that can be propagated by root cuttings:
Anchusa azurea. The beautiful blue-flowered A. azurea ‘Loddon Royalist’ is short-lived, so take regular root-cuttings in case your plant dies.
Chicorium intybus. Chicory. There are white-flowered and pink-flowered forms as well as the native blue one
Eryngium bourgattii. The blue sea holly
Geranium pratense and Geranium sanguineum
Papaver orientale. The oriental poppy
Primula denticulata. The Drumstick primrose
Pulmonaria longifolia. Not all pulmonaria will come from root cuttings but cultivars of P longifolia will.
Pulsatilla vulgaris. The Pasque Flower.
Verbascum. The perennial verbascums only
With some plants, such as the oriental poppies, roots grow close to the surface of the soil and you should be able to take some without digging up the whole plant. Simply scrape away the soil around the base of the plant until you expose some roots. Cut the roots away from the plant but remember which end made the cut (this will be important later). Put the roots into a plastic bag to prevent them from drying out and don’t forget to replace the soil around the plant. With plants whose roots tend to travel straight down, such as Verbascums, you may need to dig up the whole plant before you can cut off some of its roots. You can re-plant it afterwards.
Making and potting your cuttings is best done in your greenhouse, shed or garage. You could even clear the kitchen table. You will need some pots about 4 ins-5 ins diameter and some compost to put the cuttings in. I use compost that is a mixture of loam, grit, perlite and coir but any proprietary cuttings compost will work. Fill the pots with compost loosely: don’t press down on the compost to pack in tightly into the pot.
As with the hardwood cuttings, the very old, thick pieces of root and the very young, thin straggly ones are best discarded. Using sharp secateurs or a sharp knife cut off a piece of root that was nearest the centre of the plant with a straight cut. Now cut off, with an angled cut, a piece of root about 2 inches to 3 inches long. The roots are going to be inserted vertically into the compost and the angled cut will show you which is the bottom of the cutting. Carry on in this way until you have enough cuttings. A five inch pot will take about 5 cuttings.
Push the cuttings into the compost with the top of the roots just under the surface. The roots of some plants (such as the Japanese anemones) are too thin to be inserted into the compost and these can be laid horizontally on the top. Sprinkle about 1/8th inch layer of compost over them and finish off with the same depth of horticultural grit. The grit will stop weeds and mosses germinating and stop the compost from being splashed off the top of the pot when you are watering.
Store the pots in a greenhouse, shed, porch, spare bedroom or outside in the shelter of the house until shoots appear. Do not get too over-excited when you see the plant sprouting. Root cuttings often produce shoots before they produce any real roots of their own. Look under the pot and you should see little white roots curling through the drainage holes when your cutting is well rooted. Separate the individual cuttings and pot them up into their own pots using a potting compost. When their roots have filled this new pot you can plant them out in the garden.