Sunday, August 16, 2009

Celtis africana - African species for bonsai. (All pictures will be updated by better ones as they become available.)

Celtis africana

Celtis africana
September 2009- September 2011
Height: 12cm
Pot: Alberto

This is the first species I'm going to discuss as part of my effort to promote African species as bonsai.
This is one of the best African trees to use as bonsai. This deciduous tree is fast and easy to grow under a wide range of conditions. The trunk of Celtis africana is easy to distinguish by its smooth, pale grey to white bark. It may be loosely peeling in old trees and with horizontal ridges.
In spring Celtis africana is very lovely, with its light green, tender, new leaves that contrast beautifully with the pale bark. The leaves are simple, alternate, triangular in shape with three distinct veins from the base, and the margin is toothed for the upper two-thirds. The new leaves are bright, fresh green and hairy, and they turn darker green and become smoother as they mature.
The true size of the leave and the reduction possibilities:

Celtis africana is common and widespread in South Africa. It occurs in a wide range of habitats from the coast up to 2 100 m, from the Cape Peninsula northwards through South Africa to Ethiopia, where it grows in dense forest, on rocky outcrops, in bushveld, in open grassland, on mountain slopes, on coastal dunes, and along river banks and in kloofs.
The typical form of an old celtis in the Bushveld:
The branch/canopy structure of the tree in forests:

Derivation of the genus name Celtis is the Latin name used by Pliny, and is also the ancient Greek name for one of the plants reputed to be the lotus of the ancients. The specific epithet africana means African. Celtis africana thus means, the African celtis. C. africana is commonly known as white stinkwood.
Growing Celtis africana
Celtis africana is fast and easy to grow. It is fairly drought resistant and can withstand frost. It does best in good, rich, deep soil with plenty of water in summer. Freshly collected seed germinates easily. Seeds collected from the ground are usually infested by insects, so it is best to harvest from the tree. The flesh from the berry is best cleaned off and the seeds should be sown in a flat seedling tray filled with river sand and well decomposed compost (5 parts river sand to 1 part compost). The seeds should be covered with a thin layer of river sand and kept moist. The trays should be placed in a warm but shaded area. Germination will take 15 to 30 days.

The seeds:

Transplant the seedlings into good, rich soil and give them plenty of water and they will grow fairly fast, more than one meter per year. The tree can also be propagated by air layering in early summer when the tree is actively growing as well as root cuttings taken in spring.
Here is a thick growing root cutting:

GROWING AS BONSAI (Also for Celtis sinensis, australiensis and hybrids with africana)

Repotting is done in early spring just as the buds begins to swell. Heavy root pruning may be done as long as the top is reduced too. Big yamadori, even big trees take also well. Keep the transplanted trees in shade until the tree starts to grow. Collected material can be left in light shade for a full growing season.
It can grow in a variety of mixtures as long as it is free draining.
As the leaves reduce very well, the tree can be grown in any style. The tree can even be grown in a cascade as long as the higher growth is pinched regularly.
An example of a double trunkline literati in the making:

As the tree lose all its leaves in winter its winter form is as much appreciated as when the tree is in full foliage.
The tree back bud easily especially after heavy pruning. Styling is mainly done by wiring but bending thick branches can be done by splitting, hollowing, notching and drilling. The tree grows very fast so wires much be checked regularly.As this tree has mostly a smooth bark wire marks stay for very long. For small wounds I only use flowers of sulphur but big wounds must be sealed to prevent the tree from drying out. Big wounds take quite a long time to heal over. When doing chop and grow let the wound grow over before doing the next chop. Taper can be achieved by chop and grow, sacrifice branches and by trunk splitting and the nebari can be build by using the tourniquet method.
A splitted trunk:
 The same split trunk three years later:
The tree July 2014:

 The first buds on a healthy tree can be pinched after every leave to reduce the size of the leaves. Defoliating is not necessary to reduce the leaves, but can be done to help with the ramification of the branches.
When actively growing the tree is quite thirsty. In spring, summer and autumn keep the tree uniformly moist. In winter the tree still needs water but just enough not to dry out. The tree responds well to organic or inorganic fertilizers.
Another one I am working on bu mostly using clip and grow:

 I am seriously thinking of letting lower shoots on the nebari grow out to emphasize the "old" looking current nebari. This, also with fattening up the lower branches, will also add to the taper a bit. There are some "horse eyes" on the trunk - they do fit the nebari but not the rest of the smooth trunk. Should I find a way to let the rest of the trunk look older? Maybe patience is the answer here?

With the current nebari some very characterful surface roots will add to the picture.