ONE OF THE EASIEST WAYS TO PROPAGATE perennials is by taking root cuttings. Although the primary function of a plant’s roots is to take up moisture and nutrients and to anchor the plant in the soil, roots also have adventitious buds on their surface that, under the right conditions, can give rise to new plants.
The best time to take root cuttings is from early fall to early winter, when the plants have built up nutrient reserves for next year’s growth and are going dormant. Not every perennial lends itself to this method, however. Among the best candidates are Acanthus spp., Anchusa azurea, Japanese anemones (Anemone xhybrida), Siberian forget-me-not (Brunnera macrophylla), bleeding heart (Dicentra spp.), globe thistles (Echinops spp.), sea hollies (Eryngium spp.), ligularias, Oriental poppies (Papaver orientale), garden phlox (Phlox paniculata), primulas, rudbeckias, Stokes’s aster (Stokesia laevis), and verbascums. To demonstrate the technique, we’ve used an Oriental poppy, whose thick, fleshy roots are easy to handle. (The cultivar shown above is ‘Juliane’.)
1. Assemble your materials. You’ll need a sharp, clean knife (sterilize it with alcohol before using); rooting mix (a 50–50 blend of peat moss and perlite works well); a pencil or dowel; plastic pot; and labels.
2. Dig up the clump. Using a garden fork, gently pry the root ball from the ground. Rinse off excess soil with a hose. If you need only a few plants, you can expose and sever one or two roots rather than the whole clump.
3. Cut several firm, healthy roots from the clump, making sure to note which end is “up” (i.e., closest to the plant’s crown). The polarity of the root sections is important, and they may not sprout if planted upside down.
4. Trim the roots into approximately 2-inch sections; the precise length isn’t crucial. Cut the top part of each section level and the bottom at an angle, to remind you which end is up.
5. Plant the root sections at approximately 1-inch intervals, using a pencil or dowel to make planting holes. The top of the root sections should just be covered with rooting mix.
6. Label the pot and water the mixture, allowing all excess to drain away. Place the pot in a bright location at about room temperature (gentle bottom heat will speed up the process, however). Keep the rooting mixture moist but not soggy. Plantlets will appear in about 6 to 8 weeks; when they are a couple of inches tall, they can be potted up individually and grown on.