Sex in the Fynbos

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I love the sent of sex. In fact I am prepared to bet that most gardeners do as well. The fragrance of all the flowers are a ruse to attract birds and insects to assist in floral reproduction. Of course there are other ways of attracting a pollinating agent to a flower, namely colour which I will discuss at a later stage and nectar. So, the sutle scent of flowers is something I treasure.

There are six floral kingdoms in the world and I am fortunate enough to live in one of them, the cape Floral Kingdom. Found along the southern coast of South Africa in the Western Cape province, the kingdom extends from Cape Town in the west and Port Elizabeth in the east, a distance of about 700km. To the north it extends to the ridges of the Cape Fold mountains, a range of mountains that runs parallel to the coast, a geological testament to continental drift. In fact, if you see nothing else on a visit to the cape, marvelling at the layered folds of this mountain range will create visual memories for the rest of your life.

The Cape Floral Kingdom is diverse in plant species, a mere hectare on the top of Table Mountain reputed to contain more species of plant than the entire United Kingdom does, comprising a staggering 8500 species. Indeed, the Proteaceae comprise 1400 species alone. The reason for the diversity of species is time, time spent unfrozen. While the northern hemisphere was still buried in a cap of glacial ice, Southern Africa was basking in sunshine and plants had an extra 10,000 years of warmth to stimulate speciation. They also had their fair share of fires to contend with and it is this very factor that has made the fynbos unique.

Reproduction in the fynbos needs fire, well an aspect of it does. The soils of the fynbos are geologically old and leached making them nutrient poor, most of all in phosphates. So over time the fynbos species have developed a physiology that allows them to use the nutrients. This is also one of the reasons that the Cape Fold Mountains are some of the only un-forested mountains in the world.

The fynbos species have developed a root structure with additional microvilli to increase surface area to better absorb best the limited nutrients available to the plants. Another strategy employed is to recycle nutrients and minerals from old leaves and direct it into new growth and flowering. This is why in nature a stand of fynbos can look rather bland and downright tatty – all the lower leaves are recycled.

To apply this to growing fynbos species you need to plant them where you won’t do a lot of weeding or any manual cultivating – any disturbance to the roots introduces fungal infection, kills the roots causing the plant to wilt, die and keel over. Added to this, do not over feed the plant with fertilizer, especially phosphates. This is the toxin that will ensure the demise of your plants. In, fact when establishing a Protea orchard in 1995 our soils had to be tested for phosphate level to determine if it would be possible to cultivate them.

Pollination on Proteaceae is basically and orgy. Plenty of insect get attracted to the large and extravagant floral heads to feed on the copious nectar. In their battle to the multitude of nectarines they bustle against the anther with pollen and transfer it to the flower they visit. And this is where it gets interesting. Fertilization takes place and seeds develop. In a species like Protea cyneroides (see my photo album) each of those spiky bits is a flower, each with a potential of being pollinated. On average only 10% will be pollinated to produce a viable seed. This is another defence strategy. To fend off parasitic insects, by producing many ‘false’ seeds, the energy required to chew itself through to a viable seed acts as a deterrent to any caterpillars and the like. But it does not stop them trying.

Next in the process is the dormant stage. The viable seed in genus’s like Protea and Leucodendron remain in the ‘flower’ until the next fire. There are a few certainties in the Cape, and fires are one of them. Each year fire erupt in the fynbos and travel at unbelievable speeds, killing everything in their path. And this is the start of the next stage of fynbos reproduction. The seed heads and cones (Leucodendron spp) are not burnt. Infact on the leaf matter is burnt in the fire, the architecture of the plants remaining a stark black sculpture as a reminder. As the cones dry they open and release the seed to be dispersed by wind, ants and rodents. But one very special ingredient was provided, namely smoke molecules, one of the triggers for germination. Fynbos species are notorious for the number of triggers for germination which have to be in sequence for the seeds to germinate. Triggers include humidity, moisture, temperature, smoke, barometric pressure (for the altitude species) and in some species chemical catalysts from ant species. So it is not just a process of collecting seed and throwing them in the soil, watering them and having them pop up. Nope, you have to activate each trigger in sequence for success. The difference in germination rates when applying smoke to the seeds in seed trays increase from 10% to over 90%. I have even had some Leucodendron spp increase up to 99% by adding smoky water, an infusion made by holding a damp towel over a smoky fire and repeatedly plunging it into a bucket of water till the water smells of smoke. Pour that over your Protea seed and you will be amazed at the results.

Today I will be having a braai (Afrikaans for a barbeque) and making my smoky water to drench some Leucodendron laureolum seeds that I have sown along a ridge for a hedgerow and wind break. They are a low shrub getting to about 1.7m tall and bushing out. I will also include some L. uliginosum, a tall silvery shrub. Both have vivid cone head in flowering season with male and female plants. See photo’s.

• 26 Nov, 2009
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