** You cannot use root cuttings on variegated cultivars as new plants will have plain leaves.**
November is the time when some herbaceous plants such as phlox, acanthus and oriental poppies can be propagated by root cuttings. Select pencil-thin roots, cut into 2-4 inch lengths with a horizontal cut at the top and an angled cut at the lower end. Push them into cutting compost so that the horizontal cut is just below the surface; top-dress with grit.
Lift healthy plants when dormant (from late autumn onwards).
- Wash the roots, then select young tick roots and sever them close to the plant’s crown using a sharp blade.
- Take no more than a third of the root system from a parent plant, and replant it as soon as possible.
- Discard thin root ends, and remove any lateral roots.
- Make each root cutting at least 2-4 inches (5-10cm) long. Plants with thinner roots such as campanula and phlox need longer cuttings of 3-5 inches (8-13 cm).
- Insert about 2 inches apart into pots of moist- free-draining compost so that their tops are flush with the surface. Top-dress with 1/2 inch layer of grit.
- Place cuttings in a cold frame, or use a propagator with bottom heat.
- In spring check for roots, pot-up successful cuttings and grow on to plant out next year.