This vocationally-oriented course comprises core studies in general
horticulture plus specialised elective studies. The course is designed
to lay a foundation for a long-term career in horticulture by developing
the ability to identify a large range of plants, knowledge of essential
horticultural principles and practices and practical skills in plant
propagation, growth and care.
The average person can complete this to a minimum required level in around 150 hours. Some students may spend longer in preparation for the exams.
Pruning is something that we need to do for a variety of reasons, and the best way to prune plants varies from place to place. Some plants need to be pruned to keep them healthy and vigorous; others need pruning to improve flowering and fruiting.
Many plants can grow quite happily without needing to be pruned unless they get out of hand or develop disease. If a plant is too big for the position it is grown in, it may make more sense to replace it with a smaller-growing plant, rather than constantly cutting it back.
- Use sharp tools ….don’t bruise or tear plant tissues with rusty, blunt secateurs or loppers.
- Bypass secateurs are better than anvil type ones that tend to bruise the plant.
- Whenever you remove a part of a plant, make the cut just above or as near as possible to a bud.
- First remove weak, dead or diseased tissues.
- Next remove anything growing in the wrong place (eg. making the plant look an awkward shape, or perhaps growing over a path or another plant).
- Finally, prune to encourage or preserve the type of growth that is desired for that plant (eg. if the plant produces flowers or fruit on young wood, cut it hard to stimulate new growth. If it produces on old wood, be sure you retain sufficient older wood).
- After pruning, feed the plant with a slow release fertiliser (fast acting fertilisers do not achieve much if applied in winter when the plant is dormant).
- Dip secateurs in methylated spirits and wipe clean after each plant to reduce the spread of disease.
WHAT’S GOOD ABOUT PRUNING?
- Pruning can help to reduce disease outbreaks by removing diseased tissues and by thinning growth to allow air to circulate through the plant.
- Pruning encourages the plant to “bush up”. Frequent light clipping encourages many new shoots to form, so that the plant has a compact, bushy apperance.
- Pruning can rejuvenate old, unproductive plants. By cutting back hard into old wood, dormant buds can be forced into growth (but beware that not all plants can tolerate cutting into old wood).
- Pruning enables you to create a strong tree structure that can better hold large amounts of fruit.
- Pruning will help to improve fruiting and flowering, eg. pinching off the lead buds on tomatoes and passionfruit will cause the plants to send out bushy side shoots that bear more fruit.
- Pruning is an enjoyable exercise with immediate results that improve with time. Clippings can be recycled as mulch or ingredients for compost.
- Don’t prune plants that are cold sensitive during cold weather. Plants like Fuschias will send out tender new foliage that is susceptible to wind and frost damage if you prune them now.
Sometimes roots need pruning as well. This may be because they are growing into places where they are unwanted; or perhaps some other reason
You may want to promote a more compact root system in preparation for transplanting; or you may want to dampen the vigor of the top growth. When root systems are made smaller (eg. with bonsai), this can help keep the foliage above from getting bigger.
How to root prune:
- You may root prune when potting up a container plant; or you may dig a trench around an in ground plant to root prune it.
- First remove outer soil and untangle as much of the root mass as possible. Tease long roots out of the ball and cut them off with pruning shears. You can cut off between one-half to one-third of the roots.
- For root-bound plants, slice pieces of soil and roots off the edges of the root ball with a sharp knife--about 3cm all around--and make vertical cuts from top to bottom in several places. Then, tease out the remaining roots on the outside of the root ball.
- Root pruning will shock the plant a bit, so keep it in a low light area for several weeks and water frequently.
PRUNING DIFFERENT TYPES OF PLANTS
Every plant is different; and in different situations it needs to be pruned in different ways. By studying the fundamentals of horticulture; and plant identification, as you do in this course; you will develop a basis for making properly considered decisions about how to prune what plant, wherever you encounter it.
If you want good flowering, roses must be pruned. This is regardless of where you are, but the way you prune them varies from place to place, and depending on the type of rose. Here are some general guidelines for pruning roses:
- Most people don’t prune roses hard enough. It is difficult to kill them by pruning, but do not cut a grafted rose below the graft.
- Be careful not to damage the roots. This can cause suckers to shoot.
- Cut off suckers (shoots emerging from the roots or soil line) cleanly, any time of year.
- In warmer climates prune less, but more often. You can still cut at least 30% of the foliage off when you prune a rose, virtually wherever you are.
In cold climates (eg. Tasmania, Northern England) prune once a year in late winter.
In milder, temperate climates, a heavy winter prune and light summer prune may be appropriate.
In sub tropical places (eg. South-east Queensland) prune hard, any time of year, removing 50-70% of foliage; and you’ll get a great display of flowers around two months later.
Pruning different types of Roses:
- Standard Roses: Standards should be pruned hard early on. Thin out weak and diseased wood. Standards need to have suckers removed and the stem must be kept clean. After establishment, prune to within 1-3 buds of the last season’s growth. In later years, you can then remove about half of the previous season’s growth.
- Bush Roses: First, remove dead/diseased wood. Then shorten the shoots and branches. Strong shoots can be taken back to a length of 4-6 buds above the last season’s growth. Cut weak shoots back even further. Keep the middle of the bush clear of shoots.
- Climbing Roses: Climbing roses should only be pruned gently after planting. The branches that you want to climb should be left, unless they are very thin or shrivelled. If there are multiple stems, then cut back until you have 3 or 4 left. In later years, you can cut back old stems to allow new, healthy ones to replace them.
- Carpet (Groundcover) Roses: Thin foliage but don’t reduce the overall spread (unless the plants are encroaching on paths or other plants). The aim is to increase ventilation and encourage new shoots
Wisteria should be pruned immediately after flowering in spring. Cut back the current year’s side growth to about 15 cm. Also cut back over vigorous tendrils in summer.
How to Prune Lavender
Lavender will become spindly and bare if it’s not pruned enough. The trick with lavender is to prune often, starting when the plants are small. Tip prune small plants with secateurs to encourage a dense, compact shape. When the plants are established, cut them back with hedge shears after flowering to around 1/3 of their size.
In cold areas, wait until the new growth starts in late winter or early spring to shear the plants (autumn pruning may stimulate new shoots that are susceptible to cold damage).
Don’t cut back into old, leafless wood – the shoots won’t regrow; and don’t prune when the flowers are forming.
Bamboo hardly needs any pruning. Removing dead wood can actually remove the plant’s natural support, which is important during extreme wind, rain, snow etc. If you want to limit the growth of a bamboo, simply stamp firmly on new shoots coming up through the ground. This will prevent them from growing and keep your bamboo a bit smaller.
Prune Summer-Flowering Shrubs and Trees in Winter
Summer-flowering plants such as hydrangeas, crepe myrtles, tibouchina and hibiscus, produce their flowers on the current season’s wood (ie. stems produced after winter). Pruning these plants in winter encourages new buds and growth. In cold areas, wait until the frosts have finished before pruning.