Commercial Production of Ambrosia™ Apples in Ontario
Table of Contents
Introduction And OriginAmbrosia™ is a naturally occurring chance seedling found in 1990
in a cultivated plum orchard previously planted to Golden Delicious and
Starking Delicious in British Columbia. Its parentage is unknown but possibly
is a seedling of a cross from Starking Delicious and Golden Delicious.
After discovery, the cultivar was propagated by budding and further testing
showed the cultivar to be stable without significant reversions (Figure
1). Figure 1. Ambrosia™ is a medium to large-fruited
bi-colour apple cultivar with a unique sweet flavour. Tree CharacteristicsAmbrosia™ has an upright, growth habit, with moderate vigour, spur
fruit development and relatively low precocity (Figure 2). Its vigour
depends on soil type and rootstock and varies based on environment and
cultural management. The tree has a tendency for strong lateral branch
development and upright growth. As the tree matures, more spur pruning
may be required to maintain vigour and fruit size. In their formative
years, Ambrosia™ trees require judicial branch selection and tying
down of branches to establish productive trees that are easier to manage.
Significant tree training in the first two years after planting is very important for the overall development of well-angled fruiting branches and overall orchard management and productivity.
Figure 2. Ambrosia™ trees have an upright and
somewhat spurry growth habit similar to Red Delicious. Unlike other cultivars,
leaves remain on the trees late in the autumn. Early training and branch
tying is necessary for Vertical Axis and Slender Spindle training systems. Ambrosia™ blooms mid to late in the blossom period and produces medium pink and white flowers with broad elliptic petals. Not unlike Gala, weaker flowers on one-year-old wood open later, which have a tendency to form smaller fruit and pre-dispose the tree to fireblight because of the protracted bloom period (Figure 3). Application of a second chemical thinning spray to abscise fruitlets set from these flowers may be necessary. Ambrosia™ appears to be pollinated by any diploid cultivar flowering in the same season. Information on cold hardiness is unknown at this time, however Ambrosia™ is reported to be very sensitive to frost and cool spring temperatures. Also, similar to Red Delicious, Ambrosia™ is susceptible to dormant oil spray damage.
Figure 3. "Rat-tail" bloom of Ambrosia™
trees at flowering can lead to smaller fruit size if these fruits are
not later thinned. Fruit CharacteristicsAmbrosia™ fruit are medium in size ranging from 6.8-7.5 cm diameter
and averages 210-220 grams when adequately thinned. Fruit are globose
conical and angular in shape with slight calyx lobing and a wide eye basin.
The skin is thin and not prone to russet, with slight prominence of lenticels.
Ambrosia™ is a bi-colour apple with creamy yellow background colour
and pink/red blush that develops more red in cooler regions (ranging from
50 per cent to 90 per cent) (Figure 4). The flesh is fine-grained, cream
coloured and has a unique sweet sub-acid flavour. It has a juicy crisp
texture which, combined with its thin, glossy skin, adds to its high palatability.
Similar to Cortland and Honeycrisp, the flesh is also slow to oxidize,
and is therefore suitable for salads, fruit trays, and fresh displays. Ambrosia™ typically matures in late September to early October in Simcoe, and requires one to two picks. In cooler regions of Ontario (e.g. Durham Region), most fruit can be harvested in one pick. Fruit qualities including firmness, taste, and storage potential can be compromised by late harvest. To achieve the best red colour, do not delay harvest.
Figure 4. Ambrosia™ is a bi-coloured apple with a
pinkish red blush on creamy yellow background. Colour may be enhanced
in cooler regions, however adequate growing degree-days are required for
full fruit maturity. Considering its likely genetic parentage (Red Delicious),
it is anticipated to be better adapted to the warmer growing regions of
Ontario. Harvest TimingAmbrosia™ is a low producer of ethylene and does not display the
classic climacteric rise at harvest of many cultivars. Baseline levels
of less that 1 ppm ethylene during periods of ripening have been characterized.
Therefore internal ethylene concentrations are not a good indicator of
fruit maturity and when to start harvesting. Growers in British Columbia
use skin colour and starch staining charts for optimal harvest (Figure
5). This has helped to standardize fruit quality among growers. Therefore, the current recommendation in Ontario is to harvest Ambrosia™
based on starch index. The amount and intensity of red blush colour development
is not a good indicator of maturity as it is affected by tree nutritional
status and light and temperatures close to harvest.
Ontario research indicates that:
are all good indicators of when to begin harvest. In B.C., the average starch movement is 1.5 points per week (on a 9 point
scale), and in warm harvest periods starch movement can be more rapid
, making the harvest window of 7-10 days shorter in comparison to many
other cultivars. Colour RequirementsCurrent colour requirements for Ambrosia™ packing is 30 per cent
#4 red colour for Extra Fancy and 25 per cent #2 red colour for Fancy.
Often nearly 80 per cent of fruit can be harvested in the first pick.
Most growers fail to pick deep enough on the first harvest.
Figure 5. Use of a blush/ground colour and starch-staining
chart is recommended for determining optimal harvest. Ambrosia™ colour
charts are available to growers through the New Variety Development Council
(BC). ThinningAmbrosia™ blooms heavily and is sensitive to chemical thinning,
particularly when trees are young.
Figure 6. Ambrosia™ trees on M.9 rootstock in
their 5th leaf. Fruit size and quality have been excellent at harvest.
Judicial crop load management, tree training, and irrigation have all
helped in achieving this success. RootstocksAmbrosia™ is a low-medium vigour cultivar and therefore use a dwarf
or semi-dwarfing rootstock of M.9 EMLA or greater vigour. Trees on Malling
9 (M.9 E) have performed well for supported plantings at tight in-row
spacing. This rootstock encourages earlier fruiting of the relatively
low precocious cultivar. Disease And Insect SusceptibilitySince Ambrosia™ is a relatively new cultivar, information on its
disease and insect susceptibility profile are not well known. The information
available at this time indicates that Ambrosia™ is susceptible to
Campylomma (Mullein Bug) damage, and like Red Delicious can be prone to
mite damage. Ambrosia™ is very susceptible (perhaps equal to McIntosh)
to Venturia inaequalis (apple scab) and has a medium to high susceptibility
to Erwinia amylovora (Fire blight). StorageAmbrosia™ fruit can exhibit calyx bowl splitting, pre-mature breakdown
and soft scald if harvested over mature. CA storage reduces, but will
not adequately control flesh breakdown in late-picked fruit. Fruit tend to soften very quickly in extended regular 'air' storage;
use controlled atmosphere storage for storage beyond 60-90 days, particularly
for optimal firmness and flavour retention. Ambrosia™ should respond
well to SmartFresh (1-MCP), because of the inherently low levels of ethylene
when apples are pre-climacteric. In B.C. pre-harvest foliar calcium sprays have improved post-harvest
storage of Ambrosia™. In addition, high fruit nitrogen and low phosphorus levels have resulted
in poorly coloured fruit and lower fruit flesh firmness, suggesting that
proper care of the nutritional status of the orchard is important for
optimum fruit quality and storage potential. For current recommendations
for storing Ambrosia™ in CA, see the OMAFRA website at www.ontario.ca/crops.
AvailabilityAmbrosia™ is protected under the U.S. Plant Patent Act (Plant Patent
No. 10789). It may be propagated only by licensed parties. To prevent
oversupply, Ambrosia™ is being grown on limited acreage in Canada
and the U.S. At the time of print, all trees delivered after July 1, 2005
were subject to a royalty fee of $3.75/tree; however these fees could
be adjusted as marketing strategies are developed. Firms or individuals desiring to propagate and sell trees of Ambrosia™
must apply for a license from the Okanagan Plant Improvement Company,
4200 Hwy 97, P.O. Box 6000, Summerland, British Columbia, Canada VOH 1ZO.
Table 1. Relationship between planting density, potential
yield, and number of fruit required per tree1
1Assuming 88 count size fruit (216 gram average) at harvest
and tree are mature bearing.
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