Home => Fruit
by Laurie Meadows
Summary: If you want to grow
a small avocado tree, Pinkerton avocado is a good choice for the
backyard. Provided you have a pollinating variety. The Pinkerton
avocado variety is, in warmer climates, a winter to early spring
maturing fruit. In New Zealand's colder winter conditions, the bulk of
the crop is more likely to be mature in spring. Largest
size, but still slightly immature 'early-set' fruit can also be picked
from mid july and will have far better eating quality than any july
The Pinkerton fruit is a green skin type. The skin is thin, pliable,
and easy to peel. The flesh is smooth, oily, and is excellent eating
The Pinkerton tree is small, almost dwarf, and easily trained to a
Pinkerton has a very long flowering and fruit set period, but in New
Zealand I suspect the winter flowers will set few, if any, fruit. The
best set is likely from flowers in september and october. Pinkerton
has A type flowers, and a B type variety appears to be needed for fruit
set. Overall, this is the ideal size avocado for small garden - if the
pollenization issue can be sorted out.
Pinkerton avocado variety was originally a chance seedling selected in
Saticoy, Ventura County, California, USA by J. Pinkerton in the 1960's.
It was patented in USA in 1975. Pinkerton has been shown to be a cross
between the very compact and low winter-spring fruiting 'Rincon'
cultivar, and 'Hass'. Oxford University genetics studies in 2009 showed
Pinkerton appears to be 98% Guatemalan,
not 'part Mexican' as
previously thought. Hass is the pollen parent.
Rincon, the maternal parent, is most likely to be largely Guatemalan
with a small contribution from the Mexican avocado group. Rincon is a
small tree, only 4 meters high and wide after 10 years, and while the
fruit quality is good, the seed is large and the flesh around the seed
rather thin and subject to pressure bruises when packed for market.
Rincon's s maturity overlaps Fuerte, but Fuerte ships much better than
Rincon, so the maternal tree never found favor with growers.
Pinkerton, Rincon's offspring, has the desirable small tree size and
easy peeling of its maternal parent, and has the small seed size and
superior flavor of its paternal parent. Pinkerton looked to be the
perfect high quality early-season fruit in California. Ventura County
can be quite cold at times in winter - too cold for the 'winter
fruiting' Fuerte, the main winter variety, to reliably set fruit.
Pinkerton was seen as a variety that might fruit more reliably, as
Pinkerton is relatively cold tolerant (for an avocado). It seems that
it crops heavily in areas of California where climatic conditions suit
it, but Pinkerton needs a cross pollinizer variety to fruit well, and
it has had quite a number of problems with flesh discoloration while in
coolstore. It is also a 'greenskin' avocado variety, which attribute is
said to 'confuse consumers'. As a result its early promise has not been
realised, and Pinkerton has not gained much traction commercially - in
spite of its superb eating quality.
Winter fruiting avocados
We have two late winter fruiting avocado varieties here, Fuerte and
Pinkerton. The large Fuerte tree here is in a shaded position, and
rarely sets more than six or so fruit. Until 2014, our few Pinkerton
trees have proved equally as unproductive, even in a sunny
position. The missing factor has probably been lack of cross
pollination with a 'B' flower type avocado. No 'B' pollenizer, no fruit.
It would be gratifying if Pinkerton could be persuaded to fruit
reliably, even if only in spring. The fruit has a lot going for it. The
long-necked, pear-shaped fruit are quite large, with an very easily
peeled leathery skin, the flesh is fibre-free, smooth and buttery, it
has a very good oil content, and the seed is usually small and
separates easily from the flesh. Quite a fruit. Additionally, it seems
resistant to both the splitting and the the black rot (Anthracnose)
that can develop at the basal end of Fuerte.
The tree is low and spreading if left to grow naturally, but it is
easily trained to a single leader, and topped at 2 metres or less. In
fact, it is particularly easy to manage as a small tree - a lot easier
to manage as a very compact tree than Hass and Reed, for example.
The foliage is somewhat 'weeping' and the side branches relatively
short and lax - somewhat similar to Reed. Pinkerton has relatively
short internodes, and crowded branches need to be thinned to allow
Flowering and fruit set
Pinkerton is precocious, that is, it starts flowering and cropping very
soon after planting out. Pinkerton is an A type flowering tree. USA
experience is that it is capable of setting very big crops if B flower
type avocados are planted close by. Sharwill might be the best
pollenizer, as it sheds pollen virtually
throughout Pinkerton's lengthy flowering period. Bacon might also be
suitable, and even Fuerte (actually nominally an A type). Ettinger is
likely to be an exceptionally good pollenizer.
I have grafted Sharwill into one of the trees, and the grafted branch
started flowering in 2014 - as did a tiny Ettinger tree growing very
close by. The result appears to be a good fruit set, but a delay in the
date of the first flowers. The normal winter bloom seems to be absent,
presumably due to the crop load hogging all the resources.
Pinkerton's flowering period is very long -
right through the whole of winter and into late spring. Trees that
aren't carrying a crop have their first flowers appear in late may, but
this first 'tranche' of flowering is very slow and sporadic, with very
few flowers open on any given day, and nothing usually sets. In the
warmer parts of South Africa, where winter temperatures don't drop
below 9oC, and average winter highs are 24oC, fruit set about mid
august. New Zealand is nowhere as warm as that (average winter maximums
are around 18oC in Auckland), explaining the lack of a winter-mature
crop. If a crop does set from the winter flowering, the fruit are
'Early main flowering' starts in early spring, about early September.
Fruit that set either in very late winter or spring are pear-shaped.
Main flowering, the period of the most prolific and synchronized
flowering, is from about late september onward into october, when the
weather is warmer. This is the period, I suspect, when fruit might set.
Once again, South African experience is that in climates similar to
ours (average low 4.4oC, average high 18oC), fruit only started setting
in early october.
Pinkerton finishes flowering about the end of october. On
sunny days in october Pinkerton is likely to be in female phase at, and
soon after, midday (daylight savings time). In october males tend to be
later in the afternoon, and can remain open all night and into the next
morning (Hass sometimes does this too). While Hass does
overlap the tail end of Pinkerton's flowering period, it has 'A' type
flowers, the same as Pinkerton, and not many male stage Hass flowers
are likely to overlap the female phase in Pinkerton.
Pinkerton flowering 18 months after
Pinkerton fruit are generally
Above, wind-fall Hass, below Pinkerton early july
The pear-shaped spring set fruit have a particularly long, but
relatively broad, neck. The fruit size ranges from medium to large,
with average weights ranging from about 220 to 400 grams (some large
fruit can reach around 500 grams). The skin is slightly pebbled,
leathery, fairly thin, and easy to peel. The skin of mature fruit is
dull green, and remains green even when ripe. When Pinkerton is ripe
and ready to eat it feels firmer to gentle hand pressure than a ripe
Very-early-set fruit can be very good picked in winter (from late
june) and ripened in a bag with an apple (or other ethylene producing
fruit). If they are picked too soon, the body will ripen and be OK, if
a bit sweetish, but the neck will remain hard. It is essential to
use ethylene to ripen these barely mature fruit.
Fruit set in early spring ripen the following early spring - but can be
very good indeed as early as late august, even although they are not
fully mature. These fruit have good oil content, little or no fibre in
the flesh, and smooth creamy flesh. They do not have a pronounced
richness of flavor, however.
The main set is late october and early november (and mainly november in
slightly cooler parts of New Zealands avocado 'growable' area). These
fruit are fully ripe in september-october (and november). At this point
they have very good flavor, as well as the characteristic oiliness. (In
USA, main season fruit have from 19% to 25% oil content.) By early
november, the fruit start falling from the tree naturally. Overripe
fruit are also prone to rots, although not as bad as Hass. Some
areas may have a few late-set Pinkerton fruit ripening as late as
fruit are excellent eating, high in oil, but don't have the depth of
flavor of a well grown, fully mature, Hass fruit.
In 2003 HortResearch Ltd made a study of the
dry matter and oil content of various avocado varieties from the Bay of
Plenty. Fruit of both Pinkerton and Hass harvested between the end of
october and mid november both had similar high dry matter values of
about 29%. Hass needs to be at a minimum
of 24% dry matter before it will be able to ripen once picked. Both
fruit had an oil content of nearly 19%. In USA, 8% oil content is the
minimum legal standard for fruit for sale, and at 8% oil Pinkerton has
18.9% dry matter. USA consumer tests place 'acceptable taste' for
Pinkerton at 20% dry matter. The Pinkerton fruit with these low oil and
dry matter levels were likely to have been picked in winter. So
the natural season of maturity for the mid-late flowers (the ones most
likely to set and hold on the tree) seems to be confirmed as mid-late
Pinkerton doesn't 'store on the tree' as well as
Hass (fully mature Hass will hang on the tree for several months),
making Pinkerton a rather short season fruit once fully mature.
Firm, mature, fruit store
quite well off the tree. But fruit picked and stored on the same day
may have uneven ripening - in the sense that the odd fruit in the batch
will ripen up while the rest remain hard. These quick ripening
individuals may become overmature and have patches of a kind of
'glassy' flesh breakdown just under the skin and along the path the
(normally non-obvious) fibres take. The only visual clue a fruit in the
batch is overripe is the presence of a subtle grey-black diffuse spots
on some areas of the skin. There is some suggestive evidence that flesh
breakdown of this sort is more common in trees that have ample amounts
of nitrogen but relatively low calcium in their tissues.
Pinkerton as a winter fruit
In the photo above, the Hass fruit is a full sized but immature that
was blown off the tree on july 9th 2014. The Pinkerton fruit in the
photo was picked on size (that is, one of the largest fruit on the tree
was selected for harvest) on the 28th of june 2014, and put into a bag
with a banana to ethylene ripen. It was fully ripe and ready to eat at
the time of the photo on the 13th of july 2014. It was very, very, good.
Hass fruits in july can be good if they are a very
early set fruit, and the season has been warm. Full sized
immature Hass picked and ethylene ripened at this time are usually not
much more than 'acceptable' - a slightly grassy flavor, a bit watery,
not much oil. In contrast, this early-set Pinkerton fruit was very,
very good - oily, no wateriness at all, almost no fiber, fine, smooth
soft, almost creamy textured flesh, moderate sized seed good and even
flesh color, peeled like a dream - a first rate fruit for the time of