If there is a one-off opportunity for propagating a rare plant, all three methods of propagation using seeds, cuttings and grafting spread the risk. I have found that cuttings and seed viability are sometimes unrewarding from plants in the wild as they may have undergone stresses that are not apparent. Germinated seedlings are sometimes vulnerable to differing conditions from which they evolved and the medium-term survival rate may be low, yet a grafted plant of the same species showed remarkable growth (P. effusa).

Grafting can be used to rescue cuttings that have failed to strike roots. I received material for two proteas (P. effusa and P. witzenbergiana) from a very inaccessible area – seeds and cuttings. The cuttings that were processed had very few striking after eight weeks. The few grafts I had done all failed, leaving me with seeds and iffy cuttings. The cuttings were looking healthy above the medium but with a gentle pull (a callusing stem will swell a bit and have resistance) it seemed I may get two or three strikes out of 15. I then grafted eight of the easiest to pull out and waited. The stems were black and rotting in the rooting medium and would not have rooted although the rest of the stem and leaves above the medium looked good and must have been receiving water in the misting bed through the leaves only. After grafting two died but six started to produce new shoots three months later. The moral of the story is don’t give up – try everything. Incidentally, the seeds then germinated strongly a bit later in early winter, yet I lost most of them to damping off in early summer, leaving me with the grafts that were from the rescued cuttings as well as a few rooted cuttings. Subsequently, I did the same with some very late to root Protea acuminata cuttings so it seems as if this is an option for emergencies.

I have successfully grafted a scion from a plant that was dying from phytopthora (Mimetes stokoei) so grafting for the purpose of rescue is possible. Phytopthora kills the roots, but apparently, the stems are unaffected until all the water reserves are used up. Of eleven grafts from the dying Mimetes, only the topmost scion was successful, the lower ones had probably used up all their reserves.

Quite often the grafted entity can be more successful in the medium term and reach maturity before a cutting and certainly a seed-derived plant, thus allowing faster development of a collection. It is well known that a third-generation manipulated pot plant will give a greater percentage strike rate for cuttings and a grafted entity can yield scions within six months and even a second batch of scions within the first year (Protea mucronifolia, P. rupicola). After a few years from planting out, the grafted plant can start to fade, perhaps due to the rootstock not delivering the correct nutrients (or not the correct amount) and in these instances, the plant should have been planted into a larger pot for specialist feeding. This is an ongoing enquiry for me as to what rootstock to match with specific species.

Orothamnus zeyheri only grows on south-facing slopes at around 700 meters and above in peaty conditions with high winter rainfall plus summer cloud condensation (2000 mm per year), yet grafted plants grow well at sea level and can live without summer irrigation. The opposite also applies as grafted P. sulphurea and P. humiflora do well at sea level while their natural habitat is higher, drier, and hotter with a different soil type.

A grafted motherstock in an orchard that needs little irrigation is a better prospect than the difficulties of maintaining a potted collection on its own roots. There is always a certain amount of annual die-off of plants to anticipate (due to pathogens such as phytopthora and age) so it is wise to ensure that every year you graft enough new plants to maintain the mother stock. This will ensure that you always have young plants developing that will give good scions. An ageing plant produces progressively shorter stems yielding fewer cuttings and scions.

Recently (2020) I have started a study to determine if seeds of grafted Proteaceae are viable, and here I must thank again the Botanical Education Trust of South Africa for their funding to push this enquiry. This is in response to observations that the seeds of my grafted Protea nana and P. aristata germinate poorly and it will take a few years to have any hard results. Hand pollinating will answer if the cause is a lack of pollinators for those species. I have hand-pollinated half of the flowers of a P. nana on one grafted plant as the first step of the experiment as this grafted plant only produced 12 germinated seedlings from 60 flowers while 62 flowers from the wild (thus ungrafted) produced 184 germinations. Subsequent to the hand-pollinating exercise, germination from the hand-pollinated grafted plant versus the same open pollination grafted plant were both very low, so finding a result needs further enquiry across more species and will also require using different rootstock.

As grafting is the radical joining of two plants, it follows that if one of them is not strong and healthy, it will bring down the other so all aspects of grafting, however, small can start some weakening. I shall be discussing even the smallest detail as cross genus grafting of Mimetes onto Leucospermum is unforgiving of weak procedures. Some of these details may be relevant for only a tiny benefit in one species but may be more productive in others.

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Bypass secateurs need to be sharp and scrubbed clean with steel wool. The Felco 6 (smaller) is my choice and can be disassembled for maintenance. There are two types of knife blades that I use – a single bevel and a double bevel. Single bevel knives taper from the back of the blade to the cutting edge only on one side, the other is flat so that the cut will always deepen. A double bevel will taper equally on both sides to the cutting edge, giving the more skilled operator the option.

My most frequently used blade in this type of grafting is one of a good quality stainless steel so it does not rust (lower grade “SS” can rust) and stays sharp longer, is as thin as possible and about an 8 cm long blade, 12 mm wide and the cutting edge is straight to the tip. The longer blade means different portions of the blade can be used for consecutive cuts before needing to be sterilized. Another I use for the rind graft has a shorter blade, longer handle and a double taper. Scalpel blades tend to break in thicker wood and rust, as do snap off paper knives. I work with one single bevel, two double bevel longer blades and two double bevel short blade, two secateurs, a bark lifter that I constructed from a piece of 2 mm aluminium and two small wood carver U-shaped chisels of two sizes: 7 mm and 3 mm.

All tools should be as sharp as you can get them and maintained that way. I try to get a polished surface (it tears the face of the cut less) using the finest sharpening stone as possible (e.g., shaving hair off the forearm). Diamond sharpeners and waterstones are excellent but expensive, however a cheap oilstone is just that. It is essential to have three grades of sharpeners – extra fine, fine and medium, but to reduce costs, fine water paper can be used quite adequately. YouTube is full of knife sharpening videos.

My work bench (L- shaped) is of a kitchen type surface with a small piece of thick plastic chopping board turned on its edge, braced and clamped as a cutting surface. When the chopping board gets too scored by the knives, it can be re-faced with a carpenters’ plane. A swivel chair with a backrest and on castors with soft music helps the workday.
Plastic kitchen
chopping board
upended and
clamped

Note that the forefinger of the left hand is braced on the back of the chopping board while the thumb and forefinger grip the scion. This means there will be no movement of the scion when the right hand pushes the knife blade. By keeping both elbows close to the body, even braced against the body will give a much greater control. If the scion is hard and the knife blunt, the cut can be helped by leaning the body through the direction of the cut rather than using the forearms to push the cut.

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Immediately after the graft is completed it should be sprayed with a contact fungicide, mixed with seaweed extract (10ml /l) and salicylic acid (200mg/litre) to help the plant overcome the shock.)

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It is better to have a misting bed with timed foggers of the smallest water droplets that can be switched off in damp or humid conditions.

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Protea nana responds poorly if a thin single stem is taken, but better if a slightly thicker recent growth (this seasons) multistem scion is used in early to mid-summer. The grafting wound should then be just inside the leafless or older leaf part of the stem, however hand stripping the leaves off a P. nana does not wound the stem as deeply as in P. humiflora. A dissection microscope will tell the story.

Protea scolymocephala responds poorly to a late summer graft with the apical meristem removed, it is better to graft after the first new shoots have hardened enough (early summer) and retain the apical meristem.

This is where having ex situ plants that can be assessed daily is a tremendous advantage to the grafter. This also allows for pruning of the scion and rootstock mother plants for better stems and even disbudding to stagger new shoot development. Spraying with seaweed extract and fulvic acid is another procedure in manipulation of the motherstock, as is a spray application of a gibberellin.

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The established cutting to be used for grafting should have six to eight leaves – at grafting time the bottom two leaves will be retained while the rest will be stripped off to allow space for the scion and bindings. Naturally a too short cutting, unusable for grafting immediately will need to produce new stems that need to harden off, adding to difficulties with nursery space and time, however these give good results when the new stems have matured enough. These new stems are usually soft and do not slip the bark easily if the rind graft needs to be used, so are better with cleft or splice grafts.

Grafting on to unrooted stock does work sometimes and is operator friendly, but only under optimal conditions otherwise failures will occur frequently, so this procedure for the rarer species taken from the wild is not really an option. A cutting that starts rooting only after six weeks or more unacceptably increases the risks to the scion especially if the scion is from the wild.

I have recently grafted twenty eight Mimetes on to unrooted Leucospermum stems as a last chance attempt. However I first stood the unrooted stems in 2% sugar water for twenty four hours and the scions for four hours, grafted them and placed them under grow lights (16/8 hours photoperiod) of red/blue wavelength, watering them as needed with no misting as they were in an enclosed area. After twenty days there was no wilting but roots will only begin to show after fifty days so at the moment I am still waiting, update to follow.

Grafting on to well rooted cuttings before potting-up is rewarding, even preferential for commercial nurseries, however the roots should be well established. It seems that this type of cross genus grafting requires a well rooted stock to support it over the first few weeks at least, and this should apply for other rare species unless the scions are from a manipulated mother plant. Newly rooted cuttings often do not slip the bark easily for rind grafts, but performs better a few months after establishing a good root system.

A scion that has failed to form a callus with the stock can be pruned off and the stock potted up for new shoots to develop as these are excellent for later grafting, however there may be a co-morbidity in the rootstock so a suitable quarantine time with anti-fungal sprays is advisable before the next grafting attempt.

Established rootstock that is growing strongly may produce two or more shoots so the weakest can be pruned off. If there is plenty of scion material multiple grafts can be done on the same stock. I once grafted three different Mimeteses (M. argenteus, M. hottentoticus, M. splendidus) on to the same Leucospermum rootstock that had three good stems but I think the stock got confused with the different messages as growth flushes of these different scions occur at different times so after a while it gave up. Three different colours of leucospermum on the same rootstock might look good!

I have tried various hybrids of proteas and leucospermums and they all seem suitable as rootstock, so it comes down to what is readily available. I have mature mother plants of Protea Pink Ice and Leucospermum Veldfire. They root and receive the scion well, continuing to grow for years when planted out in an environment full of pathogens (Phytopthora, Colletotrichum, Fusarium, Dreschlera, Ilyonectria, and others). They carry well but are not complete proof against these pathogens, so some do succumb.

There are hybrids developed for specific resistance to nematodes, for compatibility with high or low Ph or for resistance to certain pathogens. I have a high incidence of Phytopthora cinnamomi and lose grafted plants quite regularly which proves that there is no proof against the “Big P”.

Quite often the rootstock, although compatible with the scion, after a few years the scion starts losing vigor and I put this down to the rootstock not delivering the correct nutrients that the scion evolved in. (Protea odorata, mucronifolia). The answer may lie in a different rootstock more closely adapted to the environment of the scion and I need to test this. A more immediate solution is not to plant them out but to keep potting-up the grafted plant as it grows over the years and manipulating the soil by way of changing the ph., additives etc.

I have recently added to further strengthening of the rootstock by flooding the medium a few days before grafting with sugar water at 2%.

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The scion stems can be harvested just before nightfall, stood in water and the grafts can be done the next morning, sugar water at 2% will help. This applies particularly to the silver mimeteses, but less to other Proteaceae although it would be good practice. My normal procedure about 30 minutes before grafting is to strip off the necessary leaves, trim 1 cm off the base and stand the stems immediately in a cup of water until they are grafted.

The root stock needs the topmost leaves stripped off, leaving the 2 lowest, and the top pruned off, allowing space for the vertical cuts plus the first binds of tape.

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I use the cleft graft (also known as “wedge”) where a vertical cut is made downwards into the prepared stock and a wedge is cut of the scion to match the depth of the stock cut, about four to five times the diameter, the scion is slipped into the cut and tied off. If the cambiums are mismatching, the scion can be set at a slight angle to the stock so that some intersection of cambiums is guaranteed. Alternatively, the scion can be set so that the cambiums are aligning on one side only or the vertical cut can be made off centre on the stock though this would be a last option.

It can happen that a knife slips when the vertical cut is made into the stock and needs a re-cut. There may be no more space on the stock so a re-cut from a ruined vertical cut for a wedge graft needs be changed into a splice graft. For this the single bevel knife is used to make the cuts on both stock and scion. The problem with a splice graft is that the faces of both cuts need to be held together before the bind, so from this perspective is not easy. This splice graft does potentially present more cambium connection.

The above techniques are appropriate if the stock and scion diameters are almost the same but with the smaller diameter scions it might be like grafting a matchstick on to a pencil so that the cambium matching is almost impossible. For this a modified rind graft using the U-shaped chisel is a much better option.

A vertical slit is cut in the stock using the short blade knife, no deeper than the cambium layer and a side to side (not a twist) movement of the blade closest to the handle will start the rind to lift. The tip of the blade remains in the bark and is the fulcrum. If needed, with clean thumb nails, the rind can be parted the length of the slit and on both sides of the vertical cut. Alternatively, the bark-lifter can be used. The scion is then scooped with the chisel the same length as the slit in the stock and gently slid behind the parted bark and tied off. The chisel naturally scoops a U-shaped groove in the scion, and this matches the round stock. If the stock is not hardened enough, quite often the bark does not lift easily and I find the bark lifter sometimes damages the cambium when thumb nails cannot do the job. Any damage to the cambium needs to be repaired in addition to callus formation so a variation is to make two vertical cuts the width of the scion (a few millimetres) and the bark between the 2 cuts is peeled downwards to expose the cambium. The scion is scooped with the chisel and inserted into the groove, the flap of the stock is trimmed a bit so that it overlaps the scion tip at the bottom and bound.

I prefer the latter rind graft as with a very thin scion (Protea nana, P. mucronifolia etc) the thinnest part of the scooped scion will nestle inside the vertical sided groove and thus be protected from a too tight binding. The thinnest scooped part of a narrow scion can be only half a millimetre thick, so will very likely be affected by a tight binding in the former rind graft that has only one slit where the bark can press down on the thinnest part of the scion under the binding.
As practise makes perfect and stem hardness varies, a simple jig shown below to hold stems should be part of the learning curve. Think in hundreds of repetitions before starting.

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