Why Plant Trees?
The world is getting hotter but especially our cities. Trees can reduce temperatures of a city by as much as 12degreesC, by providing cooling shade to people and buildings and through evapotranspiration. As trees release water in to the atmosphere, the surrounding air is cooled as the water transpires from liquid to vapour. Trees also capture carbon and reduces air pollution which are driving climate change. Carbon dioxide emitted from our factories, our vehicles, our houses is captured by trees which use the carbon to grow and releases the oxygen into the atmosphere. Trees also help to reduce flooding because their roots stabilize the soil making the soil more porous so that the water runoff is not as heavy and damaging. Finally, properties with trees could have a higher value as more people appreciate the benefits trees can bring.
Why Indigenous?
We agree then that we want to plant trees. But what should we plant?
Trees for Zambia specializes in indigenous trees because indigenous trees are home grown, they are local, native, occur naturally, and are suited to our climate altitude, soils. But most importantly, indigenous trees form an important part of the ecosystem. Our indigenous birds, insects, fungi and animals depend on them. Palm trees contribute little.
Indigenous trees are more adapted than their imported exotic cousins. They tend not to grow too big. (Have you tried removing a 50 year- old Indian Ash?) They do not invade as weeds, (Jacaranda). They are adapted to the climate and mostly can cope with periods of drought.
Indigenous trees are home grown; they are local and native; they occur naturally. Indigenous trees are suited to the local climate, altitude, soil and form an important part of their various ecosystems. We know that trees growing in the natural state have sophisticated communication and reproductive systems that links them with other trees of the same species, with other plants, soil flora and fauna in the same ecosystem.
The linkages extend to large animals, birds and insects that eat them, fertilize them, or distribute and help germinate their seeds. In addition, there are complex root-soil relationships (including fungal mycorrhyza and bacterial nodules) which are now better understood. These mutual associations assist to sustain the ecosystem because the plants and trees access and contribute nutrients, and maintain moisture conditions (and therefore life), in the soil profile. A plethora of insects (including butterflies, ants, beetles, spiders and mantids), feed on, reproduce in and often provide mutual benefits to the plants they associate with.
Many larger and small animals (kudu, duiker and bushbuck, bush babies, squirrels, bats, door mice), reptiles (chameleons, lizards and geckos, snakes), and birds of all varieties (insect, seed, fruit and nectar eaters, and birds of prey) use plant flowers and fruit for food and leaves and branches for nesting, refuge and shade. We know that maintaining diverse ecosystems and natural processes is fundamental to our survival as a species.
Indigenous trees give shape to the rural and urban landscapes, provide shade in the garden, on the streets, in car parks and on the farm. In some cases, indigenous trees increase fertility in the soil, provide lots of colour and interest – flowers, leaves, pods, seeds.
Exotic vs Indigenous Trees
Gardeners want an attractive garden with flowering trees and shrubs. Farmers want windbreaks, shade, or a nitrogen-fixing species. City planners want good street trees that do not destroy roads, give appropriate shade and are easy to maintain. Most people are more familiar with the common exotic tree species which have been introduced from tropical and temperate areas because they have attractive flowers, such as Jacaranda [tropical south America], Flamboyant [Madagascar], Spathodia/Tulip Tree [equatorial Africa]), or they have interesting leaves, [Japanese Maple], or they grow fast and give shade, Gmelina [Asia] or provide poles, Eucalytus, [Australia]. While the benefits of exotic trees cannot be denied, there are four main reasons why we should think twice before we plant them:
- It can be difficult to grow anything under exotic trees, because they often do not enjoy that well-established ecological relationship with their environment described above. Some exotic trees actively exclude other plants (Flamboyant).
- Invasive species – some have few natural controls and will spread rapidly and become pests (such as Lantana,Guava and Jacaranda).
- They can be thirsty (such as Eucalyptus) and greedy of nutrients.
- They grow fast and sometimes huge, but frequently don’t live long.
Some Choices
Returning to the discussion of indigenous trees, there are many hundreds of tree species to choose from, flowering at different times of the year, with distinct shapes and forms, attracting numerous and diverse insects and birds. Indigenous trees provide beauty and colour in the garden; shade to the market place, street, or car park; screen factories and warehouses; supply animal fodder on the farm; offer fruit and vitamins, as well as ingredients for medicinal purposes; supply building materials and fire wood; and can stabilise and give nutrition to soil.
Indigenous trees and shrubs come in a wide variety of habitat groupings, shapes, degrees of evergreen-ness, textures, forms, flower colours, seed shapes and insect, large and small animal and bird associations. Therefore, choosing what to plant depends largely on what you want from the tree and where the tree will be planted. Most indigenous trees suitable for gardens, streets and parks grow remarkably quickly with steady watering and a little tender loving care and they will last for generations.
We have selected a few trees as examples that would do well in the garden and in the city. But there are plenty more. Contact [email protected] for more information.
Acacia xanthophloea
Common Name: Fever Tree
Tall, graceful and fast growing with smooth yellow-green trunk and branches. Flowers are sweetly scented fluffy yellow balls. Used as a specimen tree and in landscaping, planted in groups for effect. Used extensively on streets of Lusaka.
Bauhinia petersiana
Common Name: Coffee or Kalahari Bauhinia
An evergreen small tree that produces a stunning display of large showy white flowers that look like paper hankies. Needs to be kept pruned or becomes untidy. Planted on several streets in Lusaka and is good as a screen plant or in a shrubbery. Fast growing.
Bridelia micrantha
Common Name: Mitzeeri
Medium to large fast growing deciduous tree, perfect shade tree. Cream coloured to light yellow flowers. Great for butterflies. Provides a splash of colour in the autumn and again in spring with its yellow, orange and purple leaves. Good in avenues. Wood is termite resistant, durable and used for furniture. Do not plant too near buildings.
Cordia africana
Common Name: Large-leaved Cordia
A large tree, fast growing, seen in State House gardens. Showy, white, sweetly scented flowers, makes a great shade tree in a large garden, flowering after profusely within a few years.
Croton gratissimus
Common Name: Lavender Croton
An attractive, ornamental and versatile deciduous small tree but is capable of becoming a large tree. Fast growing. The leaves have a beautiful and striking silvery under-surface and constantly change colour. Good in small gardens.
Dombeya rotundifolia
Common Name: Wild Pear
A small deciduous tree that produces a stunning mass of white flowers in early spring. It makes an ideal avenue tree. It also makes a very attractive specimen tree. A great tree for bees and butterflies.
Erythrina abyssinica
Common Name: Red-hot Poker Coral Tree
A medium sized deciduous tree, rounded spreading crown that produces spectacular scarlet to brick-red flowers before the new leaves appear in July and August. Great tree for the garden, is also used on banks to prevent soil erosion. Seeds used to decorate trinkets.
Khaya anthotheca
Common Name: East African Mahogany, Red Mahogany
Grows fast, especially if watered. Spectacular shape and majestic size of up to 60m. Shade tree. Long straight trunk opening up to a wide crown. New leaves are bright red, shiny and smooth. Decorative fruit. Good in large garden. Useful for urban landscaping and often used as a street tree.
Trema orientalis
Common Name: Pigeonwood
Medium sized tree with an umbrella shaped canopy that provides light, dappled shade. Grows fast.
Trichilia emetica
Common Name: Natal Mahogany, Musukili
Handsome evergreen tree with a round spreading crown. Leaves dark and glossy, flowers creamy green and fragrant. Good specimen and shade tree, ideal street, avenue and in car parks. Seen all over Lusaka. Non aggressive root system.
