by Marilyn Homewood, Master Gardener

Most of us are familiar with using stem cuttings to make a replica of a specific plant. Less commonly used in Canada are root cuttings, a form of asexual reproduction which can be used to propagate a range of herbaceous perennials and even a few woody plants in the later part of autumn when plants have gone dormant (full plant listing in references).

Last fall, I determined that I would need approximately 25 new oriental poppy (Papaver orientale) plants to place at the back border of one of my beds. “Beauty of Livermere” was already planted in another bed and I wished to have more of that variety. However, poppies have tap roots and are notoriously difficult divide. As oriental poppies do not come true from seed when looking to reproduce a particular cultivar, root cuttings seemed to be the answer.

As I had never done this before, I choose to take cuttings at more than one time – late September, late October and in the end of December when we had a surprising warm spell. I lifted a couple of plants brushing away the soil from the roots (washing would have worked better). I selected out roots with a diameter of a pencil and cut them off with secateurs taking less than 1/3 of any one plant. The donor was replanted immediately (and the crown mulched for winter protection).

Next, the roots were cut into 2–4-inch (5-10 cm) lengths making a horizontal cut at the upper end (part that was closest to the plant crown) and an angled cut at the bottom. You must preserve the polarity of the cutting. They will not grow if planted upside down. I filled pots with a 50/50 mixture of potting soil and vermiculite (perlite also works). I inserted the cuttings vertically into compost, ensuring that the angled end of the cutting was put in first to preserve polarity. The compost was watered until it was moist and then put out in my extension for the winter where they would be cool but would not freeze. Root cuttings do not require light until green growth begins to show and they can be kept in the basement if need be.

In my case, it took about 2 months before any of the cuttings showed any green. The September cuttings were a flop as only a single cutting out of 10 had growth (too early to take root cuttings). I had almost 100 % strike from both the October and December batch. The cuttings were in a high light area so as they grew on, I did repot them up. In late April, the new plants were hardened off and planted out. They grew well in their new location and I look forward to next year’s bloom.

There are other advantages to using root cuttings instead of other means of propagation:

• Root cuttings require no special aftercare (no humidity bag etc)
• Large numbers of new plants can be generated from a single parent plant (good for larger gardens)
• Plants derived from root cuttings are relatively large and vigorous
• Cuttings are taken in a quieter season when a gardener may have a bit of time (I don’t know about you, but my spring stem cuttings have a high failure rate as I don’t keep as close an eye on them as I should and they either burn up in the plastic humidity bag or dry out from lack of water)

Perennials such as Japanese anemones (Anemone hupehensis) and Phlox (Phlox paniculata) can be propagated in this way. These plants have thinner roots and contain less food reserves so it is recommended for these species to use longer sections (3-5 inches) and lay them horizontally on top of compost in a tray covering with a thin layer of compost.

Whatever plant you wish to propagate, give root cuttings a try. You may be pleasantly surprised.

Resources

Propagation by Root Cuttings (RHS)
Plant Propagation
Grow More Plants with Root Cuttings