As we head towards spring we need to think about what needs to be done before the onset of the rainy season.

Most of our winter flowering shrubs would have finished flowering and we now need to work on a pruning schedule over the next few weeks. So why do we prune?

Reduce size of the plant: during the summer months shrubs put on lots of vegetative growth and then flower in winter. Once they have finished flowering, we reduce the size of the plant by at least two-thirds, removing any excess vegetation.

Quite often we live in small gardens and need to ensure that plants fit in the space allocated. Pruning also stimulates growth and allows the plant to produce healthy new growth.

It allows sufficient light into a plant and improves the ventilation through a plant. Overgrown vegetation cuts out light, causing poor leaf growth in the centre of the shrub. Air movement and ventilation prevents pests from breeding and fungus from damaging the plant.

Repair and correct damaged parts of the plant: branches break, either because of monkeys or high winds. If not pruned these parts of the plant can cause dieback which can lead to the death of the plant.

Jagged cuts have a greater surface area exposed to the elements that become infected, whereas clean cuts heal quickly due to the formation of callus at the cut.

Remove the damaged branch by cutting just above a bud or node. Diseased tissue can spread very quickly to healthy areas of the plant. Prune back infected shoots to healthy tissue to prevent the spread of the infection.

To direct and control growth: through pruning and pinching you can stop growth on one side of the plant and allow it to grow in a different direction. By pruning to outward facing buds you achieve a vase shape of branching which is important to roses and fruit production.

It is best to prune in the juvenile stage which allows the establishment of a healthy frame and a balanced appearance. This lets the foliage grow at the correct height and position. Remove all competing leader shoots and encourage the remaining shoot to develop into strong leader. Eventually you need to have at least 3-5 well-shaped frame branches which will allow the shrub to grow into a strong plant.

Special effects: through pruning you can create artificial forms such as topiaries, hedges, standards and reduce trees to shrubs and shrubs to ground covers.

Compensation to overcome an imbalance between roots and shoots: often when trees are transplanted the roots are damaged. To compensate for damaged roots, reduce the foliage through pruning. This protects the tree from wilting and allows the balance between the roots and shoots to be in harmony.

Improve the flower/fruiting/foliage quality: the more flowers, fruits, or foliage the poorer the quality of the plant. Pruning and reducing the percentage of foliage improves the quality of the foliage and thus the flowering and fruiting. Vineyards would be a prime example of a plant that needs to be pruned every year to ensure a good yield the next season.

Four factors influencing pruning

Position of cut: must be 1mm above the bud. Too close damages the bud, too far away from the bud leads to die back. Cut must be at an angle away from the bud, encouraging outward growth from the bud.

Sanitation: all pruning implements should be sterilised with Jik before use. All large cuts must be sealed with a bituminous seal which prevents the entry of moisture, pests, and disease. Implements must be sharp to ensure a clean cut.

Environmental factors: Lack of light reaching the foliage causes weak growth. Pruning to the vase shape allows more light into the middle of the plant.

Poor air movement encourages pests and diseases. Removal of excess foliage allows good air circulation.

Excess nitrogen results in shoots that are soft and green when pruned. Through pruning the remaining branches and foliage benefit from a better ratio of nutrients.

Pruning in summer results in the bark being damaged through excessive sunshine, causing sunburn. Pruning is better in winter because plants have acclimatised to lower light intensity.

Plants that need pruning after winter:

Leonotis leonorus (wild dagga). This shrub puts on lots of vegetative growth in summer and grows into plants about 1m high. They flower during the winter months with either orange or white compact clusters of flowers down the stem. Reduce the size of the plant by at least half. Remove small side shoots and keep only the large main stems.

Hypoestes aristata (ribbon bush). Shrub of about 1.5m that produces pink to magenta flowers from March to August. Once finished flowering, reduce the shrub by half, pruning to healthy nodes. Remove damaged and diseased stems. Compost after pruning and water.

Karomia speciosa (southern Chinese hats). Shrub to small tree that produces a combination of paper-like pink and purple flowers. Flowers in summer in profusion but must be pruned every few years to keep it in shape and to size. Reduce by half, pruning back to thick healthy stems. Pruned correctly, it will grow into a compact flowering shrub.

Plectranthus ecklonii (large spur flower). Erect shrub up to 2m which must be pruned after flowering in July before the new growth appears.

Reduce by half to healthy nodes and stems. Remove all thin and diseased branches. Try to keep this shrub at about 1m high so you can enjoy the pink, white and purple flowers from March-May. – Chris Dalzell Landscapes