The distinction between tip and spur pruning is relevant to mature producing trees and not juveniles. The separate goals for very young trees are to optimise root/shoot balance at planting, minimize leaf transpiration demand and establish the desired structural form, so are not considered further here. The following comments are directed towards perennial dicotyledenous fruit trees, although brief mention is made of grape vines. The topic of tip vs spur pruning is relevant to many fruit trees but by no means all, so some of the others are mentioned to provide context.
An overview sentiment is to realize that intensive management practices such as hand pruning have been used and refined over centuries and will almost always result in better fruit productivity than doing nothing or use of comparatively crude machine pruning. The latter approaches have inevitably been forced on commercial operations for economic reasons, but they can still produce good yields that are profitable. Home growers don't have to cost their labour, so they can produce even better outcomes in yield, fruit quality and bearing regularity. The proviso to achieve these better outcomes is that they be familiar with current best practice.
To define the terms, pruning involves removal of parts of a tree and tip pruning is removal of the tips or apical regions of branches (also called pinching and heading cuts). Thinning cuts are removal of whole branches back to the supporting limb or trunk. Spurs are short compact branches, usually lateral to the main axis, with very short internodes; so spur pruning is management of these to optimise quality fruit production.
Most research on the effects of pruning on fruit trees has been done on temperate zone deciduous plants with less on sub-tropical and tropical evergreens, but some general principles have emerged.
For example: vertically directed shoots are seldom as fruitful as those that are oblique or near horizontal; winter pruning results in stronger recovery shoot growth than that in summer; numerous small cuts (tip pruning) stimulate growth more than a few large cuts (thinning); summer pruning has dwarfing effects when done over several seasons; pruning removes apical dominance and releases more proximal buds from inhibition, which then changes branching pattern and tree structure; winter pruning increases leaf and fruit N, P and K but decreases Ca and Mg, whereas summer pruning increases leaf and fruit Ca and Mg; summer pruning can decrease fruit carbohydrate content when leaves adjacent to fruit are pruned; fruit bud formation is more influenced by pruning in young trees than in older trees; and both winter and summer pruning increase fruit set.
The key to proceed on this topic is to appreciate that time of pruning can be significant, and trees almost have to be considered on an individual basis or at least in several classes because of their different flowering and fruiting behaviour – this flows through to the type of pruning appropriate for the different classes. It should be realised that pruning affects almost all physiological processes in a plant.
The main aims of pruning fruit trees are: 1. for free-standing forms, to maintain a strong framework able to withstand wind and fruit loads 2. maintain plants in specialised forms such as trellis, cordon, espalier, palmette etc 3. control size for harvesting and spraying 4. enhance yield, fruit quality (often involving fruit thinning) and regular bearing 5. minimize pest and disease load 6. Remove dead, damaged or crossing branches, water sprouts and suckers, and 7. Improve light penetration. Tip and spur pruning obviously relates to point 4, but as pruning has such widespread affects, work done addressing any of the other tree management issues may impact and interact with these.
Flowering and fruiting behaviour drives whether tip or spur pruning should be conducted. The following categories can be broadly defined: flowers and fruit form
There can sometimes be overlap between these distinctions, and others don't fit into such neat categories. For example, jujubes have deciduous fruiting laterals, and when new ones are formed each year, it is these that bear that year's crop. Others such as pawpaw are not pruned unless they've been damaged by wind or disease, or have become too tall. Blueberries are usually thinned fairly heavily each year to encourage new, vigorous fruiting wood. Regarding tip or spur pruning, fruiting wood generally has to be renewed at least every few years, no matter which approach is used each season. Pruning after harvest is a very common practice, and it should be realised that some flowering buds will inevitably be removed in accordance with the severity of the pruning operation. If flowers are borne on wood formed in the current or previous year, then tip pruning will not unduly compromise the next crop. But if fruiting occurs on older wood (ie 2-3 yr), then over-pruning of these will compromise cropping for a few years.
The following points can be made regarding the four different categories identified above:
This is by far the most common category. Flowers are typically borne on current or one-year-old wood. Usually the strategy is to prune back fruiting branches after harvest so that an increased number of new fruiting branches are formed, with subsequent enhanced opportunity for flower buds to form. To switch buds from vegetative to flowering, plants usually have to be put under mild stress conditions such as withholding watering or fertilizer and/or low temperatures. Otherwise, the intrinsic behaviour of plants after pruning is to attempt to restore the root/above-ground balance by producing numerous vegetative shoots; this has to be controlled or checked and redirected. Additional summer tip pruning or pinching is sometimes done to further increase possible fruiting laterals. Examples of trees in this category in no particular order include: annonas, mango, carissa, persimmon, kei apple, pecan, avocado, acerola, carambola, fig, moringa, the guavas, olives, macadamia, pomegranate, quince, loquat, peach, white sapote, citrus, longan, litchi and sapodilla.
Not many species bear flowers and fruit on spurs, but important examples are: apple, with some varieties terminal, cherries, some plums, pears have both spur and terminal, and almond is predominantly spur. With spurs, productivity continues for some years and thereafter decreases, so these should then be pruned back to encourage an increased number of younger spurs to develop elsewhere. Given such older wood has to be maintained on the tree, there is less need for annual pruning.
These are not relevant to the topic, but for the former include fruits in the Sapotaceae family - mamey sapote, canistel and abiu, and the latter - jackfruit, jaboticaba and cacao.
The most common and traditional method of hand pruning grapes is called spur pruning, although spurs as in apple trees don't form on the vines. Instead with this technique, canes are pruned back to short two bud laterals, and no doubt the origin of the descriptor comes from the similar appearance to real spurs. Pruning for grapes consequently follows a different theme.