Section: Nutrients

The cotyledons provide nutrients up to a certain stage of development and then none at all. To try and establish which additives were most effective to promote growth, I used Protea mundi, P. coronata, P. scolymacephela, Leucadendron salicifolium and L.lauroleum These species were selected due to availability, ease of sorting, quick germination and I have worked with them often. I sprayed a different additives onto the seedling leaves once a week to promote the optimum growth and protection while plants were in the seedling tray cells and still obtaining nutrients from their cotyledons until past the cotyledon exhaustion stage.

One hundred of a mix of these species made up each batch and there were 14 batches plus appropriate controls. After eight weeks four seedlings from each batch were slid carefully from the cell and the roots were photographed on one side with a macro lens and the seedlings replaced in the cells and their batch. After two weeks the same roots were again photographed on the same face and two weeks later again, the idea was to track root development under different spray regimes.

The various additive I used to see which were most effective were kept in 5 l cans and remixed every four weeks for the duration of the trial. Tween is a surfactant used in micropropagation to lessen surface tension, but dishwashing liquid is a cheaper option.

The different batches were treated with the following:
a) Alexin®, smoke water, Tween
b) Worm juice, fulvic acid, kelp extract
c) Worm juice, fulvic acid, Tween
d) Seaweed extract, smoke water
e) Seaweed extract, fulvic acid, Tween
f) Sugar water, fulvic acid
g) Seaweed extract, fulvic acid, Alexin, micronutrients
h) Seaweed extract, fulvic acid, smoke water
i) Seaweed extract, smoke water, Alexin
j) Smoke water, Tween
k) Control = water only

In addition four batches received different systemic or contact fungicides, but no nutrients. These also grew well while the cotyledons were not yet depleted but declined thereafter, probably due to nutrient deficiency.

Results of the experiment using different additives:

The control received water only, no nutrients and initially developed as strongly as the rest but deteriorated quicker than the treated groups as the cotyledons became depleted.

About three weeks after cotyledon exhaustion, visually the worst performers were worm juice and/or sugar water, i.e. b) c) and f). The sugar I used was of the brown (unrefined) type which probably deteriorated (fermented) over the time period. I am now using refined (white) sugar in other applications at a concentration of 2%.

A too strong smoke water mix initially developed a “burnt leaves” effect and the mix was reduced from 250:1 to 500:1. It was not possible to determine the exact concentration of smoke water nor the worm juice so it is possible that the worm juice was also too strong.

The best results were shown by treatments g) and i) containing seaweed extract+ fulvic acid (5:7), Alexin® (contains salicylic acid), micronutrients. The Alexin® (with salicylic acid amongst others) also has fulvic acid in it so the fulvic acid could be dropped.

The rest of the groups were similar in performance showing reasonable growth.

Further observations not related to the above-mentioned experiment and covering the cotyledon exhaustion stage with no nutrients showed species-specific differences, some potted up to 1-litre pots, others still in the 70ml tubes. The following responses were recorded in a minority of the seedlings: P. recondita and P. effusa showed a redding of the lower leaves, P. nana’s leaves wilted and turned brown, P. witzenbergiana’s leaves blackened, P. scolymacephala’s leaves reddened, P.pityphilla’s lower leaves blackened. Once these changes appeared, most died. Considering that this happened after the exhaustion of the cotyledons my suspicion was that a certain nutrient deficiency caused a weakening, allowing an easy entry for pathogens.

Attention should be directed at nursery conditions (too much overhead watering, too little sunlight, pathogen preventative sprays) and spray feeding with the best of the above alternated with a mix of seaweed extract and fish emulsion. This would cover the stages just before, during and after cotyledon exhaustion.

As most Proteaceae are area specific to soil types it is a continuing problem to match a specie to the nutrients it is habituated to. I add micronutrients in the hope that something will do the trick – rather a shotgun approach.

Foliar feeding in prior trials to the above showed cluster root development before cotyledon exhaustion in some, which suggests a potential to close the vulnerability gap. It would seem that foliar feeding with the optimum mix prior to cotyledon exhaustion might give impetus for the start of cluster root formation and thus a greater nutrient uptake.

Most recently I have concocted a mix that I hope covers all bases and keep batches in five litre cans that can be used in rescues of weakening plants. Seaweed extract 50 ml, fulvic acid 70 ml, micronutrients – 2ml, salicylic acid 200mg, smoke water-20ml, refined sugar-2% I am in the happy position of having made my own smoke water and now have ten litres- enough to last me 100 years or so. This mix is also used as a foliar spray and can be mixed with contact fungicides etc. The smoke water and fulvic acid are acidic so the mix I use has a ph. a bit above 4.0 and the Proteaceae are acid loving. The salicylic acid needs to be dissolved in methanol or isopropanol first and then added slowly while shaking, otherwise a precipitate forms.

I have some plastic bins with a drain plug to stand rootstock (or rescue plants) in their one litre containers in this mix prior to grafting for a few hours, then drain off the mix an hour or so before the grafting attempt.