Learn to Prune
This course is self paced, with interactive tests, following reading, practical and research tasks in each lesson. It is a very hands on course, and if you approach it seriously, your knowledge and understanding of pruning plants will increase a lot over the duration of the course.
When you come to the end of the course, you have the opportunity to undertake a comprehensive, online exam. If you pass, you will be able to download a certificate of completion in pruning; to certify to everyone and anyone that you are able to prune plants.
- one of the most valuable skills for any gardener, amateur or professional.
- Know the tools and techniques for different types of plants
- Explore appropriate pruning of lots of different plant genera
There are 9 lessons in this course:
Introduction to Pruning Plants
Types of Pruning
Tools and Equipment for Pruning
Shaping Plants -topiary, bonsai, etc
How to Manage the Prunings
How to Prune What and When - a review of dozens of different common plant genera and how to prune them
WHEN and WHY DO PLANTS NEED PRUNING?
When you prune a plant, there should always be a reason.
When you study this course; you will stander that fact, and you will be able to make appropriate decisions about whether pruning is necessary, and if so, why it should be pruned. Knowing why will then help you decide how.
Here are Five Reasons Why You Might Need to Prune Citrus
Pruning to Provide Shape
Trees are usually grown in a bush shape to make harvesting easier. The central trunk needs to be at least 50cm above ground level so that fruits don't touch the ground. Crossing branches are removed and fast-growing branches are tip pruned to encourage an open, domed canopy. To achieve this shape in a young plant wait til it is has reached a height of about 1m. Then, in spring, prune the tip of the main stem just above a bud at about 60cm above the ground. As the tree continues to grow, choose three to four strong lateral branches and prune these back to about 30cm. These will form the basis of the bush framework. Remove any shoots which emerge lower down the stem but leave single leaves on the stem because these offer protection to the stem against sun scorch.
As the tree grows more, you need to continue to remove shoots from lower down the stem. You also need to prune back the leading stems by about one third and tip prune side shoots. Any side shoots which start crossing over branches or which begin to grow towards the centre of the bush need to be removed. This is typically done in spring. By following this pattern of pruning, trees will develop the desired bushy shape. Whilst they are becoming established it may be necessary to tidy up growth with a subsequent prune in the summer.
Pruning a Standard Shape
If grown in containers, a standard is often the preferred choice. This is an upright stem with a rounded shaped upper foliage part. To achieve this shape in a young tree you'll need to first stake the tree in a container. Tie the main stem to the stake ensuring that you keep it as straight and vertical as possible. Next, you'll need to reduce the length of lateral branches by about one third. Allow the tree to grow taller than the preferred height and then cut the leader back to a healthy bud at the height you want. At this stage remove the laterals which were pruned back during the first prune, but don't cut the new younger laterals at all. These new laterals will go on to form the canopy.
Allow the tree to continue to grow. During the final stage of shaping, usually the following spring, choose the best four or five laterals. These should be fairly evenly spaced out. Keep these laterals and remove any others. Tip prune your chosen laterals by three to four buds. These will now form the framework. Continue to monitor and prune to maintain shape as you would with a citrus bush.
Renovating an Old Tree
Trees which have lost their shape or which have overhanging and unwanted branches may be pruned to improve them. Sometimes branches lower down the trunk are removed.
Trees which have become unproductive can be cut back harshly in spring to rejuvenate them. This works particularly well with orange and lemon trees. The tree is cut back to what is referred to as a skeleton where only the main structure is left. All thin branches and foliage are removed and the narrowest limbs left are about 2cm in diameter. This stimulates the trees into producing new growth so that after a couple of seasons they will bear a good yield of fruit.
When undertaking this type of surgery, or any other significant pruning which involves significant defoliation, the trunk and limbs should be whitewashed to prevent them from becoming sun scorched. If it does get scorched, the bark will crack and split open rendering the tree weak and susceptible to diseases, and ultimately affected limbs may die. Extensive splitting could kill the tree. It is also advisable to seal any cuts which are wider than 2cm with a bituminous tree sealant. Citrus trees will produce new growth along the sealed limbs.
Pruning to Improve Fruit Quality
Fruit quality on some trees, such as those of early Imperial mandarins, may be improved by pruning, as the fruit in the heavy crop year may become uneven in size and have a dry pulp. The early Imperial trees may have over-dense bushy growth which limits light penetration. Pruning out several large sections of the tree (chunk pruning) improves light penetration and increases fruit size. The pruned areas may have vigorous regrowth with greater number of fruit produced so regular pruning will be required to maintain quality fruit production of the trees.
Pruning to Improve Tree Health
Tree health can be improved by pruning to remove diseased branches and fruit.
The presence of low branches close to the ground on some trees can encourage snail or insect damage. Fruit on these low branches can also spoil on coming into contact with soil and weeds. Pruning of lower branches (sometime called “skirting”) can help resolve this problem and gives clearance between the tree branches and the ground, thus improving aeration.
Correct timing of this type of pruning is however very important. Navel oranges such as Washington and Leng should be skirted before the trees flower as this will allow time for compensation of lost growth. If pruned during flowering or fruit set, yields can be greatly reduced. For other Navel varieties such as Valencia and Lanes Late, skirting can be spread over two or more years to minimise fruit loss, especially in the heavy crop year.
If trees are prone to Citrus Gall Wasp, then swellings appear as the wasp lays its eggs in the stems. There is no effective chemical control for these Wasps. The galls should therefore be pruned off as they appear and they should be destroyed. This should be done before the wasps hatch out and re-infest the tree and orchard. Yellow sticky traps hung in the tree can trap the adult wasps as they fly around the tree.