Today we are talking about the marula (Sclerocarya birrea), a tree of African origin that is gaining international fame for the properties of its essential oils and its fruits. The use of this species gives much to talk about: from ancient remedies and spells without scientific basis from the African tribes of origin, or their use in cosmetics, to true analysis of its compounds and possible use. In Spain we will not be able to grow marula because of the climate, but it is worth knowing that this species of the savannah exists.
It is an endemic species on the African continent and on the island of Madagascar. As we can see in the image, according to the biodiversity database gbif.org, Sclerocarya birrea is found in the sub-Saharan area that extends to the south of the continent. According to the elevation data with the areas where its presence has been recorded, the marula has not been found above 1600 m above sea level. It must be said that there are 3 subspecies.
- S. birrea subsp. birrea
- S. birrea subsp. caffra
- S. birrea subsp. multifoliolata
And if we make these three known, it is because some of them have been found at altitudes of up to 2000 m, although it is not usual. The distribution of this species is obviously not only due to altitude. The image below shows the distribution of the 3 subspecies.
The marula tree is a large tree. Relatively low trunk and very extensive crown proportionally speaking. It can easily measure 18-20 meters, although its most common dimensions are about 10m.
There is no excessive evidence of the maximum age of a marula specimen, but long-lived species of more than 200 years of subsp. caffra in South Africa.
It is a dioecious species and therefore has trees that are well differentiated into male individuals and female individuals. Kiwi is another typically dioecious tree. The reproductive stage of the marula begins naturally at 4 or 5 years.
EDAPHOCLIMATIC CONDITIONS OF SCLEROCARYA BIRREA
Given the previous distribution, we can define that the birrea subspecies is mainly found in the equatorial zone. The caffra subspecies is found in the southern areas and on the island of Madagascar. The multifoliolata subspecies is found in much less quantity in the humid zones of the Tanzania region mainly. This very particular distribution influences the thermal regimes of each subspecies. In the equatorial areas the ranges are more stable and somewhat higher than in the southern areas of the continent. At the equator they have an average annual temperature of between 22 and 29ºC, while in the southern areas and Madagascar they are around 19-26 of average annual temperature.
Remember that this is an ANNUAL average temperature. This means that there will be many days of the year that exceed 30ºC and that frosts are non-existent, not even temperatures below 10ºC at night. Madrid, for example, a typical Spanish city with very hot summers and cold winters, has an average annual temperature of about 14-15ºC.
Severe cold damage is observed at -4ºC in species living in southern Africa.
It needs direct exposure to the sun. The typical savanna climate and other more tropical ones (remember that the savannah has a very humid season and another very dry one) make the exposure of this tree to the star king is direct and a lot.
It mainly occurs in soils with a loamy or sandy-loam texture, although somewhat tolerant specimens have been found in slightly clayey soils, although with a good fraction of sand. Cases are mentioned in heavy soils (silty or clayey) but it is somewhat testimonial and in some of the subspecies, specifically Sclerocarya birrea subsp . caffra . Heavy soils are generally considered unsuitable for this species.
How do we measure soil texture? / su_note].
Regarding the pH of the soil, we find a range between 5 and 7, that is, slightly acidic since the most frequent values are at an approximate pH of 6.0. Extreme values of 4.8 have been found but this is not the most common. All this shows a wide range of soil pH ranges that translate into good tolerance to changes in this sense, even if we have slightly acid soil values that are optimal.
The species is associated with a strongly seasonal pattern. Annual rainfall should be between 500 and 1200 mm. Depending on where each of the subspecies occurs, variations are observed in the monthly distribution of rainfall. For example, for subsp. birrea usually occur between 5 and 7 months of 50 mm of rain per month on average. In another subspecies like caffra that occurs in slightly more humid conditions; 6 to 9 months of rainfall of more than 50 mm reaching annual totals of 1200-1600 mm.
In areas of Madagascar and South Africa the birrea subspecies does not occur (this occurs in the sub-Saharan area), however, subsp. birrea is more tolerant to drought, having found specimens with rainfall only 2 to 3 months higher than 50 mm. And finally, the subsp. multifoliolata is also from much more humid regions and is the least abundant of the three.
USE OF MARULA FRUIT
And here we enter the multiple uses of marula. Both in their continent of origin and in the West. What reaches the West commercialized is in the form of liquor. Specifically the Amarula liquor that we can see in many shops. Marula essential oil is also sold for nutritional purposes and in many cosmetics such as hair masks among many other applications. It is also in many of the lipsticks as an important ingredient. In the next section we will see a little about the active principles that make it interesting.
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BUT WHAT IS THE FRUIT LIKE AND WHAT IS IT USED FOR IN THE PLACES OF ORIGIN?
For local communities in Africa, marula is a global resource for the entire year. Its wood, its fruit, its roots, the bark, the leaves are used. Everything from the tree is used with greater or lesser success from a nutritional, functional or medicinal point of view.
- As a fresh fruit in Africa it is widely consumed. Its meat contains a lot of vitamin C (400 mg / 100g), practically twice that of orange, making it an important contribution to the usual diet of people who eat it fresh. The sugar content is between 7 and 16%.
- Historically, beer has been made with the pulp of marula, although we do not know if there is any commercial currently. In particular, we are sure that it continues to be done. In fact, animals such as elephants have been seen with symptoms of intoxication when eating naturally fermented marula nuts. In the fermentation process it can reach a higher alcohol content than wine and elephants in particular love this fruit.
- The infused leaves help in poor digestion . They are also an important food for endemic species in the growing areas of this tree.
- As you can see, there is an amarula liqueur cream. Its characteristic flavor has made it worthy of an internationally marketed drink.
- But the most appreciated, without a doubt, is marula oil . We are going to develop this point a little more.
MARULA OIL, THE MOST PRECIOUS FOR COSMETICS
Marula nuts have a low moisture content and a high content of fat and protein above all. They have important mineral fractions. Therefore, it is an edible, nutritious nut with a great interest in the industry for various purposes.
First of all, the walnut is edible, hence marula oil as well. Contains between 53 and 61% oil. It is light yellow in color and soaps can be made with it. The saponifiable lipids are comparable in quantity with those of olive oil. Its iodine number is also similar to that of olive oil, so its percentage of unsaturation is also high, better resisting oxidation and being a healthier oil.
From this it follows that it is so precious in cosmetics because its oxidative stability is 10 times higher than that of olive oil and therefore very suitable in this field. In Africa it is used as a meat preservative. In Spain olive is used as a preservative. Orza loin, sausages in oil … Each country makes use of what is close to it!
On the other hand, its amount of tocopherols is relatively low, so sunflower oil exceeds it in this case. This results in a lower vitamin E content. But you can’t have it all! Some will wonder. If it is low in tocopherols (which is a great antioxidant), how is it possible that it is so stable to oxidation? This resistance is attributed to high oleic acids, although in later studies it has been concluded that other fatty acids also present a minor influence.
Thanks to all these properties, marula oil has been used in:
- Cosmetics . Many cosmetic lines use marula oil.
- In the food industry (not much seen) such as frying oil, baby food or nut coatings.
- For soap , thanks to its saponifiable characteristic
- Aromatherapy oil .
- Even as a sunscreen, although we already know that solar oils have the totally opposite effect, so it is not a suitable use.
- As a moisturizing oil for the skin.
MEDICINAL PROPERTIES ATTRIBUTED TO MARULA
Traditionally, marula has been used, with or without success for various medicinal uses in Africa and in various rituals. We must emphasize that all these references do not have any scientific endorsement that corroborates it with proven active principles. They are traditional uses of Africa. We’re not saying they work except for a couple of proven uses.
- The bark has been used in decoctions, infusions or extractors to treat malaria, venereal diseases, diabetes, dysentery, hemorrhoids, stomach ulcers even to treat malaria but we have not found scientific studies that support this, except antidiarrheal properties due to the presence of procyanidin , a type of tannin also present in grape seeds.
- The leaves are rich in flavonoids . Traditionally they have also been used infused for diarrhea or macerated with the bark for insect bites or skin irritations.
- The roots have been used in Tanzania boiled in water to treat scabies.
- The stems, mixed with the bark, have been mixed with sodium carbonate to treat dysentery.
- Fermented fruit
With the idea of giving as wide a dimension as possible the magnitude and importance of cultivation in Africa we also want to collect the ritual and cultural uses of African societies.
- In Nigeria, the bark is used as protection against snake bites.
- The bark extract is mixed with other ingredients for use in ablutions (washing the body in order to purify it).
- Marula bark extract is also cooked with millet flower and butter and eaten before hunting until the prey is hunted. It is believed to protect against the spirits of hunted prey .
- The bark extract can also lift curses and help trap sorcerers .
- Numerous rituals are done around the marula trees.
With the great interest of its fruit and seed, the marula thus becomes a crop of interest . Small producers are known to have introduced it to South America. Regardless of whether or not it is right to take species from continent to continent, it seems that the marula does well in the tropical climates of South America, as is to be expected. Countries like Paraguay have marula crops brought from Africa since the species is not endemic to America.
MARULA SEED GERMINATION.
Marula has a hard nut that must be prepared for germination from seed. In addition, it must be “awakened” from its latency period.
Seed dormancy can be broken through the following process:
- The skin and pulp of the walnut are carefully removed.
- The nuts are dried in the sun for at least seven days (taking into account the temperatures of their endemic area). If the temperatures are lower than the annual average expressed above, more time is required.
- Store the dried walnuts in a well ventilated and shady place and expose them to low temperatures below 10ºC in winter.
- Seed protection in the strict sense is very thin and is not a barrier to germination. However, for faster germination, the scarification process is required or it is soaked for 12-24 hours to weaken the operculum.
Under suitable conditions, germination can last as little as four days or up to four weeks, during which time practically 100% of the seeds germinate. The germination process and first care will last from 3 to 6 months before transplanting it to the field. All depending on the irrigation, the climate and the chosen or available substrate.
The sowing season will be highly variable depending on the climate, latitude and altitude, but as a clear reference it should be sown at the beginning of the rainy season. By the time the transplant is carried out (minimum 3 months) the seedlings will already be about 30cm tall.
As a vegetative propagation, grafting seems to be the best solution, being able to have fructifications 3 years after grafting.
SOME BASIC TIPS FOR MANAGING MARULA CULTIVATION
- It must be kept in frost-free and hot, very hot and dry areas.
- They are resistant to drought .
- Direct exposure to the sun for proper growth and, above all, good fruiting.
- The wind protection is also very important. Being a very hot climate, an excess of wind can dry out the shoots, dry out the new leaves, pull the flowers and the immature fruits of the trees.
- Although we have seen that it has a certain tolerance to different types of soil, it must be said that if you want to cultivate to obtain fruit, good drainage is necessary . With poor drainage, marula may exist but will not flower or bear fruit.
- It is deep-rooted so the soil must be too. At least 3 meters. It must also be aerated, dry and sandy loam.
- Subscribing can be done especially during the first year at the rate of about 5kg of manure per tree at the beginning of the rainy season and another 5kg at the end.
- During the first two years the irrigation regime should be about 10 liters every 15 days per tree in the dry period. Drip irrigation is one of the best ways to achieve homogeneous irrigation.
We hope this information about the marula tree has piqued your interest in this African species. All this information has been collected, translated and republished from the following bibliographic reference where much more detailed information comes.