Cuttings are the clonal multiplication of the mother plant, thus it is important to choose the strongest stems from the strongest mother plant that is free of pathogens as the best as well as the worst is replicated. Cuttings taken from mother stock that are of third generation from cuttings have a better percentage strike rate than stems from the wild. Selected hybrid mother plants that are potted so they can be manipulated would be optimal.
Proteaceae cuttings root slowly so count on six weeks and longer but this can be speeded up with heating cables. For the best results, the harvest time of the year (and time of the day), the quality of stems, a heating bed, misting, glasshouse environment, temperatures, rooting hormone and aftercare must come together. A root temperature around 22-24 deg C with a cooler leaf is optimal.
The stem should not be too soft from new growth. To test this, it should bend fairly easily but not to the extent that it can bend back on to itself. Wounding the bottom of the stem can speed up the rooting time and increase the rooting success rate. This can be done easily enough with the blade tip of the secateurs – two vertical slits opposite each other in the bark prior to the IBA dip but take care not to wound too deeply. This is not easily done with stems that are very thin so dragging the stem over a piece of sandpaper will do the trick and sandpaper comes in different grades to suit the stems. Grip the thin stem between the thumb and second finger and gently push down with the forefinger while dragging.
Leucospermum cuttings can be taken when growth has stopped in early Autumn and before the start of the flowering time in winter. This will result in rootstock available in early summer to be used for grafting. Each protea species varies in its growth and flowering time somewhere between early Summer and early Autumn however this can be manipulated by pruning the mother plant. Mimeteses have other problems in that most develop new growth and then immediately start the development of the inflorescence, allowing little or no time for hardening off. I find that pruning off the inflorescence as it commences will start new shoots that will, in time, provide stems for cuttings or scions. Mimetes species start their inflorescence development at different times of the year – some in Spring/early Summer (M. hottentoticus, M. arboreus, M. argenteus) others in Autumn or early Winter (M. stokoei, M. splendidus, M. saxatilis, M. capitulatus, M. chrysanthus)
The best time of day for harvesting is early in the morning and the stems should be stood in water until processed. The leaves of the silver mimetes show dehydration far quicker than anything else so as an experiment I took stems before dawn, mid-day and after dark and grafted them without putting them in water. The first wilted quickly (turned grey), probably due to this being the time they suck the most water from the roots, and the rest followed. I then took some more stems and stood them in water for five days with no dehydration evident. This dehydration probably applies equally to Proteas and leucospermums yet they do not show the dehydration nearly as much. The needle like leaves of some Proteas show nothing until they fall off.
If the harvested stems are collected from some distance away they should be kept cool in a plastic bag with water in it and can then be processed even 24 hours later, though the sooner the better. On a long collecting trip a well-insulated cool box with ice works well.
For an experiment I took long stems of the hybrid Protea Pink Ice and left them at room temperature for 24 hours. I then placed half of them in a bucket of water for two hours while I processed the others by trimming and dipping in IBA for cuttings, most of these dry stems developed blackened leaves almost immediately. The stems in the bucket of water were then processed for cuttings in the same way and a week later were still looking good in the mist bed. It is common practice in the Protea cut flower trade to stand harvested stems in a 2% solution of sugar overnight to stop this leaf blackening.
In warmer weather the number of leaves can be reduced to limit transpiration and the misting environment should have fine droplets with the frequency adjusted according to the day temperature and humidity. Large droplets should not form on the leaves as this will reduce transpiration.
For a rooting hormone I use IBA only at 4000 ppm for a five second dip though this concentration and dip time can be reduced if the stems are particularly young or soft and requirements can vary slightly between species. To test if the cutting is callusing and thus swelling, a gentle pull to test resistance will give the answer while removing the cutting completely from the rooting bag does not seem to set back the rooting process if there are no roots showing. The initial roots are very fragile and can fall off easily. A clear rooting bag with plenty of air holes will allow the rootlets to show on both sides of the bag before potting up. If they are showing on only one side of the bag only it probably means that the root system is not developed enough. Often, when all the rooting medium is shaken off it will show that the roots showing on one side only have a single attachment to the main stem.