A couple of months ago I started a trial of some different “Premium” potting mixes, it has been a fairly cool start to spring so seedling growth was a little slow, and some seedlings had gotten frosted and died but most of the plants have now grown enough to see any differences.
The Contestants (Callistemon citrinus)
Before I continue, the results are for the conditions present in the nursery at that time, in different circumstances mixes may perform differently. All of the bought mixes could have done with better drainage but they were tested as they were straight out of the bag.
Rocky Point Premium was the narrow winner, good growth, good colour, like the others it could have done with better drainage (better control of the irrigation system would have helped but I’ve found the more expensive irrigation timers just aren’t as reliable).
Rocky Point Premium, the overall winner.
Okay, I may have been a little biased here but in second place “Paul’s Mystery Mix” (coir, pearlite, charcoal and slow release fertiliser), showing quite good growth however the new growth on the Callistemon is distinctly paler than from the other mixes, probably from a nutrient deficiency, I’ll give it a water of fish emulsion and see if that improves the colour, otherwise I was quite pleased. The mix is considerably lighter than the others.
“Paul’s Mystery Mix”, good growth but paler foliage.
Searles Premium into third, though not that far behind the previous two.
Searles Premium, another good performer.
Rocky Point Eco, while not a “Premium” blend the plants grew ok and while noticeably slower than the others they look fine, addition of slow release fertiliser to the blend probably would have brought it up to the standard of the others. I’ll probably throw some slow release into the pots and give a water of fish emulsion to give them a boost.
Rocky Point Eco, noticeably behind the first three but plants looking healthy enough.
Earthcore Premium, the seedlings pretty well did nothing, visually it was the worst looking mix and performance wise under the trial conditions it was by far the worst. The mix might work for potting on more advanced plants but I wouldn’t recommend it for growing tubestock.
Earthcore, it may be fine under other conditions but under these it performed very poorly.
Results were similar with the Bulbine Lily (Bulbine bulbosa) Searles and Rocky Point Premiums performing well and Earthcore not so well.
L-R: Rocky Point, Searles, Earthcore.
In conclusion, “Premium” doesn’t necessarily mean the mix will be good for your purposes. All mixes could have done with better drainage (except the “PMM”) or better control of the irrigation, the “Mystery Mix” performed as well as the 2 better “Premium” mixes, though requires more effort to mix (but if you’re adding perlite or slow release fertiliser to any of the others then time saving by getting a premix won’t be that great), it is, however, a bit lighter which in a nursery with volunteers is an important factor.
The Rocky Point Eco could have done with some slow release fertiliser and perlite but given those additions should be quite fine when you can’t find either the Searles or Rocky Point Premium.