Planting into 1 litre pots at radicle emergence has a greater chance of damping off while the 500 ml size less so, but tapered cells of about 70ml with a greater aeration potential to volume came out tops. (Fig 2) Possibly the much smaller surface area of the smallest pot lessens the area of penetration for air-borne pathogens. Perhaps a larger pot does not eliminate excess water effectively (or holds more water as the radical does not use much), resulting in over watering.

My observation is that over-watering is a significant cause of failure at the seedling stage, especially if the surface area is constantly wet after potting up into I litre pots. To avoid this requires setting up a separate environment and watering system. (Fig. 9) A clear plastic rain roof needs to be in place as the warmer temperatures during spring rain is the prime time for pathogens.

After potting up into 1 litre pots, the water should be delivered via a dripper system which delivers the water to below the surface of the potting medium. I use the Netafim system with emitters delivering 2 or 4 litres/hour (6 and 8 litres/hr emitters are also available). via an 8 or 4-way manifold to arrow drippers that are spiked in close to the roots. The timing of the pulse should be about 8 seconds during the night up to first light and about 55 minutes apart. This should deliver somewhere in the region of 10 to 15ml of water per arrow dripper in each pulse from an eight-way combination manifold and is an excellent way of reducing overall water consumption. A specialist timer is needed, available from good irrigation specialists.

Water quantity is then dependent on the frequency of the longer “dry” time, as well as the “water on” time. The idea is to deliver as little water as needed to the roots rather than the surface as it seems that a constantly damp surface provided by an overhead spray causes problems with pathogens. This should be monitored by having a drip tray under the pot, the idea is to have less water penetrating through the medium and then wasted by dripping out. One of the arrow drippers should be in a clear container to monitor the volume of water passing through. The amount required depends on ambient temperatures as well as the species. The different emitters can be utilised to service different sized plants on a long dripper feedline. Fertigation can be delivered with this system but adds complications. I prefer to use 8-1-5 (N-P-K) slow-release granular fertiliser in the medium when potting up the seedlings.

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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.

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When potting up from the 70 ml cells into 500 ml or 1 litre pots, I use white yogurt containers (ex-supermarket) with holes burnt in the bottom and sides using a soldering iron.

The white containers reflect the sun and keep the roots appreciably cooler and side holes allow greater air circulation. A thermometer inside on the sunward side and another on the lee side proved this conclusively when compared to black containers. Roots will migrate from the hotter side to the cooler, so rotating the containers will set back roots on the new sunny side. Recycled yoghurt containers last for two or three seasons before they become brittle. It is good practice to give the used containers a bath in sodium hypochlorite (bleach), or a disinfectant, just before re-using.

It is my wish that tall square white pots with four vertical inside ribs with side ventilation become available. At present these are only available in black but painting them white does not work well as the paint flakes off fairly soon.

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