Boabs and Baobabs

2012/05/16 deej 0

Most people have barely heard of baobabs, or boabs as they’re more commonly called in Australia. It’s odd, since we’re one of the few places in the world which has a native baobab species – the Australian Boab, Adansonia gregorii.

There are only eight species of baobab. Of the other seven, one is native to Africa (Adansonia digitata, the African Baobab), and the other six (Adansonia grandidieri, Adansonia madagascariensis, Adansonia perrieri, Adansonia rubrostipa, Adansonia suarezensis, and Adansonia za) are endemic to Madagascar.

All baobabs are extremely drought tolerant and hardy. Some are as little as 3m tall, while others are up to 30m in height, but all have massive trunks which can reach 15m in diameter. The massive trunk may be cylindrical, bottle shaped, tapering, or irregular; thick tapering branches resembling a root-system extend from the trunk, which is why baobabs have often been referred to as upside-down trees. The wood is fibrous and soft, under a thick layer of bark, and stores water for dry periods.

The wood can be chewed to provide moisture and relieve thirst; humans as well as certain animals eat it in times of drought. The roots can be tapped for water. The trunk of the tree often develops a hollow, which fills with water during the rainy season and acts as a reservoire during the dry season. Water inside the trunk of a baobab remains potable for months, apparently due to natural preservatives leached by the living wood that keep water from fouling. This may be an adaptation to prevent microbes breeding in the water and infecting the tree, which may have water in the trunk for several months or even years at a time.

Baobabs are semi-deciduous, and may lose their leaves and become dormant for several months of the year. This period depends on the environmental conditions in the area. Under good conditions, growth can be quite rapid, up to 2m in 2 years. Trees will begin producing flowers and fruit after 8 – 25 years, and some species may live for up to 1000 years.

Flowers are large, showy, and highly scented. Although pollinated by fruit bats, the flowers are also a favorite nectar source for bees. The fruit consists of a hard, woody outer shell surrounding an arrangement of segments similar to those of a citrus fruit, with angular pockets of soft pulp surrounding a cluster of hard, black, kidney-shaped seeds. The pulp may be white, yellowish or pinkish in color, and is dry when ripe. It is rich in vitamin C, provitamin A, B complex vitamins (B1, B2, B6), calcium, phosphorus, and iron, and is described as having an acid gingerbread flavour. It forms a mealy solid, but a few hours in the sun dries it into an off-white powder. It can also be beaten into thin, leathery pancakes which can be stored for an extended period. This powdery substance is soaked in water to provide a refreshing drink somewhat reminiscent of lemonade, which is also used to treat fevers and other complaints. The seeds are also reported to be edible.

Each matured plant may produce 30 kg or more of fruit per year. Harvest the fruit when it falls to the ground, or pick ripe fruit if it can be reached. The fruits themselves are unusual in that they remain dangling during the dry season long after the tree sheds its leaves. They are also unusual in remaining edible far past the point where other fruits would have decayed into putrefaction. Stored under normal ambient conditions, they keep for up to 3 months.

Seeds can be collected from picked or fallen fruit. After crushing the hard woody shell of the fruit, the seeds can be extracted from the dry acidic pulp. Baobab seeds have very hard seed coats and germination is usually less than 20%. In nature, dormancy is broken by passage through the digestive system of large mammals. In cultivation, dormancy may be broken by immersing the seed in hot water for five minutes, by manually scarifying the seed coat, or by acid scarification for 6 – 12 hours. Unless pretreated, seeds can take a year to germinate. Seedlings have big, flat and paired cotyledons, and the first leaves are generally narrow, simple and linear. Effective protection against livestock is essential after planting the seedlings.

The leaves (of at least the African Baobab) may be eaten as a green vegetable, sometimes steamed and eaten as a side-dish like spinach, but most often ground up in soups, stews, sauces, relishes, and condiments. They contain high levels of provitamin A. The leaves may be dried, and keep well in this form, without losing their glutinous polysaccharides. To maintain a high level of provitamin A level in dried leaves, it is important not to dry the leaves in the sun. The sprout of a young tree can be eaten like asparagus, and the tap root of very young trees is also edible.


What baobabs need:

    • Water – anywhere from 200 to 1200mm of rain or irrigation per year. Baobabs are very tolerant, and can survive both arid and subtropical climates.


    • Sunlight – Lots of it. Baobabs naturally grow as solitary trees, or as top level canopy trees..


    • Soil They will grow on many different soils, but deep, calcerous soils are best. Baobabs reportedly tolerate laterite as well as relatively alkaline (e.g. limestone) soils.


  • Space – Baobabs are large trees, up to 30m tall and 10 – 15m in trunk diameter. They grow slowly, but wherever you plant a baobab you must plan for it to expend over its lifetime.


What baobabs have to offer:

    • Edible leaves and fruit.


    • Water storage in trunk hollows, and an emergency water supply in the wood itself.


  • Seeds, which can be grown into more baobab trees, either to plant out or for their edible tap roots.


What baobabs do not like:

  • Soggy or waterlogged soils, or even seasonal inundation.


  • Heavy clay soils.


  • Frost (especially when young).



Images sourced from Wikimedia Commons:

Trees and Water

2012/05/15 deej 2

No scheme water, and no bore or rainwater tanks in place, made irrigation over the summer a very labour intensive task. So every weekend we filled up a couple’ve barrels with water and drove them up to Gallifrey, then manually transferred the water to the water tubes around each of the trees using watering cans.

We tried a few water containers, and experiment showed that the recycled plastic olive barrels fitted with taps were the best. The flexible plastic water bladders that we tried first didn’t hold much water, and sprung leaks after two or three uses. The plastic slimline rainwater tank from Bunnings was better, but the lid didn’t seal, and the tap attachment wouldn’t take a regular hose, meaning that we had to siphon water out from the top. Slow.

It could have been worse; our neighbour thought we were manually watering each of the tree seedlings every weekend. The water tube tree guards were a life saver; they’re UV resistant plastic tree guards with a built-in 20L water bladder and a dripper in the base. The water drips out slowly over (in theory) 2 weeks. In hot weather the water in the water tube expands, forcing the drip rate to increase, while in cooler weather and at night when the plant requires less water the drip rate decreases.

So far, we have four fig trees (Ficus carica), all different varieties, two pomegranates (Punica granatum), a natal plum (Carissa macrocarpa), an acerola cherry (Malpighia glabra), two honey locusts (Gleditsia triacanthos), a baby boab (Adansonia gregorii), three kei apples (Dovyalis caffra), and four moringas (Moringa oleifera) planted. Those are the food trees. Yes, boabs count as food trees. There are also two oak trees (Quercus spp., acorns collected from Stirling Gardens in Perth), a dieback resistant jarrah seedling (Eucalyptus marginata) that a friend gave us, a few dozen wattles, mainly Acacia victoria, but also some Acacia acuminata and Acacia pycnantha, a few pink siris (Albizia julibrissin), and one or two black locust trees (Robinia pseudoacacia).

The plan is to plant a shelter belt around the entire perimeter, inside the mandatory firebreak, consisting of thorny natal plum, kei apple, boysenberry (Rubus x boysenberry) and sea buckthorn (Hippophae rhamnoides), as well as fire retardant trees like oaks, maples, sweetgum, hazel and prickly pear. Eventually, it will be a noise buffering fire barrier in the form of a hedgerow. Inside that will be a secondary firebreak, planted with grain and meadow plants in winter, and space loving succulents and vegetables like squash in the summer. Inside that will be the forest, and the house.

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