I kept some records of what worked and didn’t work during the 2020 season. The overall success rate for the season was about 75% (75% of cuttings survived to be potted up). This is about the same as the 2019 season. The average is dragged down by a much lower success rate early in the season when it is colder/darker and cuttings with thicker hollow stems are taken (rejecting these cuttings would result in a higher success rate). Cuttings taken from March on had about an 80% success rate. Also as the season progressed there was a reduction in time taken to root.
I found that an open sand bed in the greenhouse with soil warming cable and cuttings covered by fleece and shaded did almost as well as my main temperature & light controlled propagator in a shed. A second temperature & light controlled propagator appeared to do less well. But this reflects problems getting the light and heat levels right early in the season when it was used most, and greater use of cells (see below).
Cell trays generally did less well than plugs, pots or trays, as I had more difficulty keeping moisture levels right. I found full & half seed trays performed best in terms of rooting, though untangling roots when potting up is more of an issue than when cells are used, so suspect plants from the cells might grow more strongly/quickly after potting up.
I tried a range of different rooting media this year. Notably successful was the use of simple sharp sand, especially where this was more of a gritty/coarse mix. Less successful were the mixes that included vermiculite with general purpose compost. I suspect these moisture retentive mixes would be more successful later in the season, so to be considered next year.
These are small samples, so hopefully when I add further data the results will become more informative.
Fairplace 