No Peat, No Panic: A Winter Windowsill Root-Off Between Three Cutting Composts
Photo: peat-free cutting compost in pots with fuchsia cuttings on a UK windowsill, via i.redd.it
Peat-free compost has come a long way since the days when a bag could behave like a wet sponge or a dust bowl. Propagation is still the acid test. On 8 November 2026 I lined up four mixes on a cold, north-facing windowsill in Leeds: three peat-free cutting composts sold for the job, plus a traditional peat-based cutting compost as a control. The aim was not to crown a brand. It was to see how each mix behaved when light was low, the radiator was off and the only heat came from the room.
The setup
Eight fuchsia cuttings per mix, taken from the same overwintered plant. Each cutting had two leaf nodes above the compost, lower leaves removed and no hormone powder. I used identical 7cm pots and covered each tray with the same type of clear bag to keep humidity consistent. Bags were opened for ten minutes every few days. No bottom heat. Room temperature sat around 16-18C by day and 12-14C at night. I checked every three days for callus, roots, leaf drop, mould and pot weight.
Root score was simple: 0 for none, 5 for a dense, branched rootball filling the pot. This was a windowsill comparison, not a replicated laboratory trial, so treat the numbers as a guide rather than a verdict from on high.
The four mixes
A was a coir-based peat-free cutting compost. B was a wood-fibre and bark mix. C was a green-waste and loam blend. D was the peat control. Prices in November 2026 were roughly £5.99, £6.50, £4.99 and £5.49 for 10 litres. Based on a 0.2-litre pot, that worked out at about 12p, 13p, 10p and 11p per cutting, before pots, bags or electricity.
What happened
| Mix | First callus | First roots | Root score (0-5) | Leaf drop | Cost per cutting |
|---|---|---|---|---|---|
| A coir | day 8 | day 15 | 3 | 2/8 | 12p |
| B wood fibre | day 9 | day 17 | 4 | 1/8 | 13p |
| C green waste | day 7 | day 14 | 4 | 3/8 | 10p |
| D peat control | day 7 | day 13 | 5 | 1/8 | 11p |
The peat control was quickest, but the best peat-free mix was only a few days behind. In a winter windowsill trial, that is not a chasm. The bigger differences were in watering and consistency.
A rooted well but dried out fast. Pots needed water every three or four days, and two cuttings yellowed before roots were established. One rotted at the base by day 20. B was steadier: slower to callus, but the roots were clean, white and well branched, and the surface did not swing from dry to soggy. C was the cheapest and rooted early, but it was variable. Two pots stayed wet for too long, algae appeared on the surface and one cutting produced brown root tips. D was the easiest of the four to manage, with even moisture and strong roots.
Watering is the real divide
Peat-free mixes are not one thing. Coir wicks and dries. Wood fibre holds structure but can sit wet. Green-waste compost varies from bag to bag. The most useful tool was a cheap kitchen scale. I weighed a pot after watering, then watered when it had lost roughly a quarter of its weight. The surface colour lied repeatedly.
Clear bags slow evaporation, so ventilation matters. A sealed bag with wet compost and warm winter room air is an invitation to mould. Opening the bag for ten minutes every few days was enough here, and I removed any yellowing leaves before they turned to mush.
The recipe I would use again
By volume: 55% coir, 25% fine bark or wood fibre, 20% perlite or horticultural grit. For a greener version, swap 15% of the coir for sieved green-waste compost, but sieve to 5mm and use it fresh. No added feed; cuttings do not need it until roots are working. Pre-wet the mix, firm it lightly, water by weight and keep the bag vented.
That blend cost me about 11-14p per cutting depending on where I bought the ingredients. It was more predictable than the cheapest bag and closer to peat in behaviour than I expected.
The verdict
Peat-free cutting compost can match peat if you manage water and air. The best bought peat-free mix here was B, but a simple coir, bark and perlite blend gave me the control I wanted. Peat still wins on autopilot. Peat-free wins if you are willing to weigh, sieve and ventilate. No excuses, but also no miracles: the compost is only half the job.
