Tamarillos are small, shrubby trees that fruit on current season’s growth. The yield, fruit size and season of maturity can all be readily manipulated by the time and severity of pruning.
The results outlined in this article come from an unpublished pruning trial conducted by Drs Greg Pringle, Kevin Patterson and Grant Thorp (now of HortResearch) in Kerikeri during the early 1980s, and are used with their permission.


Plate 1: Moderately pruned tamarillo in a Katikati orchard

The basic pruning strategy for tamarillos is to maintain a sturdy framework with new growth originating from the previous season’s wood.
This sturdy framework is important due to the brittle nature of tamarillo wood. Compact, sturdy trees are less prone to breakage than leggy trees, and they can also be picked satisfactorily from the ground.
It is also important to cut back into the previous season’s wood when pruning, as cutting into older wood gives a much more variable response, usually being comparatively unfruitful. It is normal practice to remove dead or broken branches at the annual spring pruning.
The time of pruning influences the time at which the following season’s crop will mature. After pruning, there is a period when it appears as if nothing is happening before the new growth starts. This period is a little longer under the lower temperatures that generally prevail in early spring as compared to those likely to be experienced some weeks later in mid to late spring. However, as new season’s flowers are produced on new season’s growth, the new growth must occur before flowers are produced, and this is influenced by the time of pruning.
It takes approximately 20-26 weeks from fruit set to maturity, so the earlier the fruit is set, the earlier the harvesting season is likely to be. So early season pruning leads to an early harvesting season and late pruning leads to a late harvesting season (Figure 4). The severity of pruning influences the potential yield, fruit size and season of maturity. A general principle of pruning is that the harder the cut, the more vigorous the vegetative response is likely to be.
The heaviest and earliest crops will be produced by unpruned trees (see Figure 1). Light pruning gives rise to weak regrowth that branches and sets flowers quickly and in turn leads to reasonably heavy and early maturing crops.
Hard pruning, on the other hand, gives rise to more vigorous regrowth, provided the tree is not cut back to old wood. Some of these regrowths may be so vigorous they need to be pinched out at the appropriate height to cause branching and flower production in a tree manageable from the ground. Such vigorous regrowth takes longer to reach the stage where flowers are produced and so has the tendency to delay the harvest season, as compared to more moderate pruning.


1.  Total yield from mature tamarillo trees with pruning to different degrees and at
different times (August 1, September 8 and October 15).


2. Fruit numbers from mature tamarillo trees under the same set of pruning regimes.

Fruit size is also affected by the severity of pruning (Figure 3). Unpruned trees produce many fruit on weak multi-branches shoots and this gives the potential for high fruit numbers at the expense of fruit size.
At the other end of the scale, hard pruning leads to a small number of more vigorous and substantial shoots which tend to produce lower numbers of large fruit. Moderate pruning comes somewhere in between. The response to pruning in fruit size is, of course, limited by the genetics of the tree. It is not possible to get very large fruit from a small fruited variety simply by hard pruning. They can only be as big as their genetics dictate.
Water shoots have thick green stems with long internodes. They tend to originate either from the main trunk of from deep within the canopy. They bear few fruit and only serve to direct the plant’s resources away from the remaining crop. As such, they should be pruned out completely as they arise during the growing season.
Time and severity of pruning can then be used as a means of manipulating the yield and season of the crop as well as fruit size.
There may be many reasons for a grower larger fruit size. Each individual case must be judged on its own merits and treated accordingly.
These variations in pruning can be used to get a comparatively steady, but very long harvesting season from April to November by pruning different blocks over an extended period of time from early spring to early summer. They could also be used to get either an early or late crop for economic, management or other reasons.


Plate 2. Moderately pruned tamarillo in a Tauranga orchard
showing the quantity of growth removed.

Returns for tamarillos, like other seasonal crops, tend to be highest when supplies are short at the beginning or end of the season. So an early harvest, where a significant percentage of the crop is harvested by the end of May , can be worthwhile.
However, to get the most out of a very early season crop requires a lot of time in select picking the earliest fruit to get them onto the market as early as possible.
Over the years, it has been noted that returns from the New Zealand market tend to be at their lowest in June through to August, when supplies are normally heaviest. From September onwards, prices can be expected to rise as supplies dwindle.
On the New Zealand market, large fruit will normally get a better return than medium or small fruit. However, with the high returns early in the season, earliness could be expected to be more important than fruit size at the very start of the season.
Export requirements seem to be for a reasonable, medium-sized fruit, rather than the very largest. This must be taken into the equation by growers producing for export.


Plate 3. The response to hard pruning is vigorous growth
with a moderate number of large-sized fruit.

It is always a good policy to keep in touch with the chosen exporter over the specifications required, including fruit size, and if necessary adjust the orchard management to meet them.
On sites with a greater risk of getting a winter frost, it would be desirable to have most of the fruit off early, before the high risk period in June and July.
It may also be that tamarillos have to be worked into a mixed orchard calendar and manipulating the harvest time to suit is a worthwhile practice.
Where a grower deals with a lot of kiwifruit harvesting from sometime in April to early June, an early tamarillo crop would be a complication, as it could also be for growers producing a feijoas or passionfruit. Conversely, with satsuma and Clementine mandarins that can run on through into August, it would be more convenient to get the tamarillos in early and be well through their season before the mandarins get into full swing.


Fig. 3. Mean fruit size from mature tamarillo trees under various
pruning regimes. Note that higher graes equate to smaller fruit;
the very heavy pruning treatment had the largest fruit.

Yield, fruit number, fruit size and season of maturity of tamarillos are all affected by the timing and severity of pruning. The earliest and heaviest yields of the smallest fruit are produced on unpruned trees. The largest and latest maturing fruit are produced by pruning hard and late. There are no overall recommendations, but each grower can take this basic information and use it how it best fits into the overall management of the orchard.


Fig. 4. Cumulative progression of harvest season from
September pruned trees with different degrees of pruning.
The last harvest (day 122) corresponds to August 13.

Based on an article in the August 1996 issue of ‘The Orchardist’, magazine of the New Zealand Fruitgrowers Federation (PO Box 2175, Wellington, New Zealand).