PROTEAS AND RELATIVES: PROPAGATION AND OBSERVATIONS

Seeds, Cuttings and Grafts

By Robbie Thomas

Introduction

Over the last seventeen years of my retirement, I have become increasingly interested in the propagation of Proteaceae. My aim is to find ways to propagate rare proteas as well as other members of the family and record the findings so the plants and the methods of propagating them will not be lost to future generations.

These observations have been made in my small experimental nursery in the Western Cape, South Africa in the coastal village of Bettys Bay some 100 kilometres SE from Cape Town.

A big thanks to Professor Braam van Wyk who suggested I should write up my findings and kindly made many corrections.  I do not sell plants as this is my hobby and I donate plants to friends and gardens.

The Botanical Education Trust has funded this and further research and to them, a grateful thanks as my infrastructure and consumables were in a sorry state. Also thanks for all the help I have received from professionals, some of my early questions must have seemed like another sort of botanical pathogen visiting them. Thanks also to the sometimes significant tiny bits of information gleaned from conversations with non-professionals and importantly their questions helped formulate accurate responses.

Family support has been invaluable, my daughter and husband are rehabilitating and restoring degraded riverine areas and there is endless cross-ventilation there. My wife Vicki is a noted botanical artist and has painted many of my horticultural efforts and helped with the editing and drawings. My late mother was an apprentice horticulturist at Kirstenbosch starting at eighteen years old and was immersed there for the rest of her life – something rubbed off on me even though I went surfing and fishing for a while.

Propogation Methods

Protea seeds

Collecting seed from plants in the wild requires permission as indigenous plants are protected by law. Removing seed heads from a plant should be done with secateurs as snapping them off allows a greater opportunity for pathogen entry into the plant. No more than 10%...

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Propagation by cutting

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...

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Reasons for grafting

Soil types vary considerably and Proteaceae are fine-tuned for their particular soil type while a hybrid rootstock generally has a wider tolerance. Compared to the scion, the rootstock may also have a resistance to nematodes, certain pathogens, drought, high or low...

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The role of fire

Central to Fynbos ecology is the role played by the periodic fires and its smoke, and apart from the interval between them, the intensity of the flames. The shorter the interval, the cooler the fire, as there has not been enough time for a build-up of combustible material though this is not always the case as abnormal dryness and wind conditions can vary. The plants have evolved survival strategies spread over many thousands of fire intervals. Fynbos is in balance with fire intervals of around 12 years or more, but unfortunately in recent times the interval is reducing. As more frequent human induced fires have been occurring for a very short time, the natural evolution of seed storage and germination strategies lie in the deep past and one must assume that the majority of fires that started over previous millions of years were caused by lightning or earthquakes (leading to falling rocks). In the mountainous fynbos region of the Cape, the lightning season is around the equinoxes,...

Temperature and germination

I believe there is an additional influence that plays a part in the germination of the nut-like seeds: that of a colder pulse during the winter’s natural temperature fluctuations of day and night. I had not been able to germinate seeds of Mimetes stokoei and M. arboreus using naturally occurring winter temperature fluctuations in my area (about 8 deg C at night and 15 deg C during the day) and was attempting yet again to germinate seed during the winter temperature variations when our area received a colder than average winter cold front that delivered snow to the higher parts and intermittent hail for five days to some of my seed trays that were in the open. A few weeks after this they germinated well, while there was no germination from the batch that I had subjected to a hot pulse to imitate a fire. Apart from the hot pulse the two batches received the same pre-treatments. My impression is that the seeds were waiting for the temperatures of a “normal” winter to drop further, thus...

Protea seeds

Collecting seed from plants in the wild requires permission as indigenous plants are protected by law. Removing seed heads from a plant should be done with secateurs as snapping them off allows a greater opportunity for pathogen entry into the plant. No more than 10% should be taken from a plant and not more than 10% from a population to allow for sustainability. The majority of Protea species retain their seeds for a few years on the plant and are mature nine months after flowering has ended. After a few years on the plant the seed viability starts to deteriorate due to water penetration and insect predation (Fig. 1). Collected seed heads should be allowed to spontaneously open and release the seeds which takes a few days. Some proteas open very slowly so with secateurs, nibble away the bracts to the edge of the seed receptacle (Protea repens, P. scolymocephala). Viable protea seeds are generally fatter with a slightly different shape (Fig. 2). The best way to test viability is to...

Storage

In order to store all seeds for several months I use a “dead” fridge as an airtight cupboard and glass jars with a rubber gasket. After a year or so most seeds tend to start losing viability, so this storage is to span the gap between collecting and germination attempts. A paper packet does not restrict air and moisture and screw top plastic jars or zipper bags are not always airtight. Moisture is the core factor for deterioration and can cause the quickest decline so if needed I add silica gel of the type that changes colour as it absorbs moisture. Some Fynbos seeds require a maturation period before they can germinate so they do need to be stored, sometimes for a number of years. A few months before attempting germination certain seeds benefit from a striation period of one to three months in a domestic fridge which is normally at 5 deg C., however I do not usually use this option as it is not a decisive aid for Proteaceae.

Pre-germination treatment of Protea seeds

Ideally, sorted viable seeds should be soaked in 50 deg C plain water for 30 minutes in a vacuum flask to maintain that temperature. This is more of a sanitation than a dormancy break step. A further soak for 12 hours in 1% hydrogen peroxide (H2O2) as well as a drop of a gibberellin, these are an added extra, and not entirely needed. The seeds should be rinsed and dried briefly so that the hairs fluff up as they are easier to handle when sown into seeds trays. At this stage a dusting of a fungicide should be applied by putting the seeds into a plastic bag and shaking. Smoke water works well for a variety of seeds but less so for some of the Proteas and much less for the hard nut-like seeds of the Leucospermum and Mimetes. For an exhaustive analysis of the effects of smoke water access v the relevant pdf in the index. With difficult-to-sort seeds it would be easiest to try germinate the entire batch and use a larger seed tray, however the seeds will then be mixed with bracts and other...

Post germination treatment

The sowing medium (peatmoss) should be a uniform dark colour and by not adding perlite/styrofoam/vermiculite it enables one to see the white radicle as it starts to emerge and at about 1 cm in length planted into cells or pots. Tweezers are perfect for scratching in the seed tray, picking out (carefully) the seed from the peatmoss, prodding a hole in the new medium and setting the seed, radicle down. If the radicle is a bit long, you run the risk of setting the seed with a bent root so a little pruning of the tip of the rootlet may be necessary, snipping scissors work well for this purpose. At 1 cm long the emerging radicle has no root hairs, therefore there is little chance of interrupting development by this procedure. When the radicle is a few centimetres long, the delicate root hairs are just starting to grow at the top and these are very fragile. At cotyledon emergence the cotyledons have control and afford protection - I prefer to think of the cotyledons as providing “mothers...

Leucospermum seeds

Figure 4. Removal of protective coats on achene (seed) to aid germination The hard, nut-like seeds of leucospermums and mimeteses are not stored in the canopy of the plant, instead, they drop out of the flower when mature. The seeds are collected by the ants common to the fynbos and store them underground where they eat off the surrounding elaiosome – a soft fleshy skin rich in nutrients, notably lipids and proteins. It is the reward to the ants for all the hard work of dragging them underground to their nests. These nests are usually a short distance from the plant, so seed dispersion is not as wide as hairy Protea seeds that are dispersed by wind. Once underground they are reasonably safe from mice and rats. As the soft skin surrounding the inner nut has a distinctive smell recognized by the ants and mice, there is a competition as to who gets there first. The ants preserve them, the mice eat them. The conditions inside the ants’ nest provide a steady, non-fluctuating soil...

Mimetes Seeds

Mimetes have the same ant helpers at seed drop, however some produce more and smaller seeds than the others. Mimetes hottentoticus, M. argenteus, M. arboreus, M. splendidus, M. saxatilis, M. chrysanthus and M. fimbrifolius produce 0 to 2 large seeds per floret while the M. capitulates (the first seeds on the sunward side are ripe earlier) and M. hirtus 0 to 5 seeds and Orothamnus zeyheri up to 18 seeds and these last 3 are more fragile and should be treated with care. Members of Mimetes have individual florets, varying up to 30 on an inflorescence and yield a maximum of 2 seeds per floret, with an average of 10% producing seeds per inflorescence. The seeds visually resemble those of Leucospermum , have the same pollinators, ant dispersal and storage. Bagging them is the best way for seed collection and the heads can be pruned off when seeds are seen in the bag or when shoots start developing immediately below the lowest floret. Exceptions are M. capitulatus and M. hirtus that have...

Leucadendron seeds

Figure 6. Leucadendron cone with seed Some leucadendrons have nut-like seeds (e.g. Leucadendron argenteum, tinctum) which are treated the same way as Leucospermum and Mimetes seeds, but most have cones that produce flat winged seeds that require far less attention to germinate. The cones are retained on the plant for a few years and the insect predation and water penetration is far less, however the current year’s seed cones are likely to be immature and 3 to 4-year-old cones are beginning to age. Simply snap off the 1 to 2 year-old cone, dry till they open and shake the seeds out. The seeds are flat and can fall out from amongst the “scales” of the dried cone quite easily but may need a knocking to get them all out. At worst, a spike may be needed to prise them out. Most of the seeds are viable and germination can be initiated a bit earlier in the year as they seem to be less reliant on steep temperature fluctuations. Plant the seeds from early Autumn in full sun, about 1 cm deep in...

Orothamnus seeds

Figure 7. Orothamnus seedhead and achene (seed) The monotypic Orothamnus (only species O. zeyheri) is different in that the seed (technically a fruit classified as an achene) maturity and release happen quickly so the seed heads should be picked a few hours before seed drop. This is indicated by the floret bracts first becoming semi-transparent and browning/whitening as the red colour fades. (Figure 5) The bracts then reflex backwards within an hour or so and the seeds drop out with their parachute. They can be bagged easily as the floret hangs downwards, however a rain-soaked bag in a strong wind can get too heavy. It is easier to use a small rubber band to close the floret as the reflexing backward is not strong enough to overpower the rubber band. Orothamnus whilst flowering will have another flower bud developing immediately behind the first with another just starting behind the second, so bagging can be a problem then. These smaller seeds as well as the M. capitulates and M....