Midsummer onwards is the time to take cuttings from some perennials, climbers, shrubs and trees. Stems of periwinkle, passion flower, hebe, box, bay and holly, for example, have now got six to eight weeks of new season’s growth under their belts and they are at the semi-ripe (or semi-hardwood) stage. Take a shoot between your fingers and bend it. If it’s pliable and hardening at the base, then it’s half-ripe and ready for you to take a cutting.
Helping cuttings to grow roots
We want cuttings to produce roots as quickly as possible. That’s because roots anchor the plant in the soil, act like straws in seeking out and absorbing water and minerals from the soil, and store extra food for future use. Once this system is set up, then it’s time to for the cuttings to start growing strongly from the top again.
All plants have rooting hormones but gardeners sometimes also apply something extra in order to get a plant to produce more and denser roots. This increases the growth potential of the cutting, and so the plant’s chance of survival.
You could use commercially prepared hormone rooting compound or home prepared compounds such as willow tea or soluble aspirin (whose active ingredient is also present in willow). Honey water (see link) made from natural (non-heated), dark honey has anti-bacterial properties and is said to help rooting. Cinnamon powder is said to act as a fungicide.
How to take semi-ripe cuttings
Get your cuttings mixture organised: buy it or make it yourself from half all-purpose compost and half sharp sand or vermiculite. Fill some 9cm (3in) pots.
Select your semi-ripe cuttings from this season’s growth. Suitable cutting material will be available from midsummer to mid-autumn. Choose good-looking typical shoots which, for preference, haven’t flowered.
Cut just below a leaf to give you a stem about 15-20cm (6-8in) long.
Strip off any surplus leaves carefully at the bottom of the cutting. Nip off the growing tip if it’s very soft, and cut any large leaves in half to reduce water loss. This will give you a prepared cutting about 10-15cm (4-6in) long.
Apply your chosen rooting hormone, anti-bacterial or anti-fungal agent to the cut.
Insert about 5cm (2in) of cutting into the pot. Water well and allow to drain.
Place the cuttings in a greenhouse or cold frame, away from direct sunshine but not dark. Or you could cover pots with a plastic bag and put in a warm, light position, out of direct sunlight.
Remove excess moisture from inside the plastic bag but keep the compost damp.
The cuttings should root in six to eight weeks. Then feed them with a general liquid feed for a couple of weeks. Pot into single pots once the roots are well established and they have started to grow at the top.
Watch this Gardeners’ World video to be sure.
What actually works?
I’ve had my share of cuttings failures. This year I’ll be running a small experiment with four pots: one without anything extra, one with commercially produced hormone rooting powder, one with soluble aspirin, one with honey water. Oh, make that five, to include one with powdered cinnamon. I’ll let you know how I get on. [October 2016. Edited to add that soluble aspirin is way out ahead, followed by ‘nothing extra’. Interesting.]