Now that the main growing season for perennial herbs is coming to an end, it’s a great time to trim back any overgrown herbs and use the cuttings to get some new plants started, ready to plant out in spring. Here’s a few tips from the propagation notes that are included (along with many more handy fact sheets!) in each of my garden design packages.
- Take softwood cuttings from growing tips of plant (spring, early summer), or hardwood cuttings at end of growing season (with a heel – that’s the daggy bit that tears off the main stem when you pull a twig down and off).
- For hardwood cuttings, you can dip in honey or willow water to assist root development.
- 10-15cm long cuttings are ideal
- Mediterranean herbs (e.g. rosemary, thyme, sage), ornamental perennials such as salvia and geraniums, vigorous leafy herbs such as all types of mint and lemon balm can be grown from cuttings, as well as many native shrubs and ground covers.
- Remove leaves from lower half of cutting – leaf nodes and end of cutting are where roots will develop (some people cut them off carefully, others strip them straight down the stem).
- Cut back or trim off most leaves from upper half to reduce transpiration until roots have developed. Otherwise the cutting can dry out too quickly as it can’t replace the moisture lost each day through its leaves.
- Use a dibber (e.g. stick, pencil) to prepare planting holes in a pot of moist seed raising mix – don’t use the cutting to poke its own hole.
- Plant lots of cuttings close together – some will strike, others won’t – thin out in a few weeks when you can see which ones are successful.
- Water in with half-strength seaweed solution. Keep cuttings moist with regular watering, misting, saucers and/or cloches but beware of creating a hothouse in summer that could cook your plants.
- Place cuttings in moderate shade for first few days, then gradually expose to dappled light and eventually full sun (depending on variety).
- When white roots start to emerge at base of pot, the new plants are ready to plant out.
- Divide carefully and transplant to garden or larger pots.
With a bit of practice and trial and error, you’ll be able to make many generations of new plants from old – and share and swap them with friends and neighbours. For more detailed propagation instructions, have a look at Angus Stewart’s book ‘Let’s Propagate’, available from bookshops and libraries. Happy growing!