Louise Curley

23 Aug 2021 15:16

Greenhouse Cuttings

Now’s a great time to take cuttings of half-hardy and tender plants so that you have a stash of plants next spring just in case the parent plants don’t survive the winter. It also means you can build up your collection of favourite plants for free. Plants such as penstemons, salvias, pelargoniums, lemon verbena, fuchsias and lavender can all be propagated now and it’s surprisingly easy. It helps if you have a greenhouse to overwinter the cuttings so that they’re protected from the elements, but if you don’t you can keep them on a windowsill indoors.

Cuttings taken at this time of year are known as semi-ripe cuttings, which are distinguished by having woody, ripened growth at the base and soft, bendy growth at the growing tip.

How to take semi-ripe cuttings

  • Look for sideshoots that are healthy, undamaged and free from pests.
  • Use sharp, clean secateurs to remove stems about 15cm long, cutting above a bud on the parent plant.
  • If you’re taking lots of cuttings it’s a good idea to pop them in a clear plastic bag to stop the stems from wilting. Keep the bags sealed and somewhere cool and shady until you’re ready to pot up the cuttings, which should be as quickly as possible.
  • Fill 9cm pots with a specialist cuttings compost or create a 50:50 mix of compost and perlite. For cuttings to root quickly they need a light, airy growing medium that isn’t rich in nutrients.
  • Trim the cuttings by cutting them to below the lowest sets of leaves – just below the nodes where leaves form is where the plant accumulates hormones that will encourage the stem to form roots.
  • For each cutting remove the lowest sets of leaves and pinch out the growing tip so that you’re left with two sets of leaves.
  • Dip the base of each stem in hormone rooting powder and tap off any excess, then push the cuttings into the compost around the edge of the pot. You should be able to get four into a 9cm pot.
  • Water well and allow the pots to drain.
  • Most cuttings will benefit from some extra moisture around them to prevent them from wilting. Specialist growers use misting units but you can create a similar environment by placing clear plastic bags over the pots. However, too much moisture can cause rot, so it’s important to remove the bags each day to ventilate the plants and remove the condensation that will have built up on the inside of the bag before replacing.

To speed up the rooting process place the pots on a heated propagator. Don’t worry if you don’t have one, a bright windowsill is just as good, it’s just the process will take a little bit longer.

When you can see roots poking out from the base of the pots it’s time to move the cuttings into individual pots filled with John Innes No 1 compost. Over winter keep the compost moist but not too wet, and check over the plants for any signs of fungal disease – furry growth and moulds – removing any plants that show any signs of this to stop the problem spreading.