Palmer is a semi-dwarf, monoembryonic* variety with elongated purple-red coloured fruit. The variety originated from unknown parentage in Florida, USA, in 1945.
Palmer was first introduced to Australia from Puerto Rico in 1979 as part of the Queensland Department's mango introduction and evaluation program. It is grown commercially in Queensland but is only a minor variety..
* Refer to Glossary
- ground colour - green-yellow
- blush colour - dark red all over
- shape - ovate elongate*
- stem end shape - level
- beak - insignificant
- weight - 300-800 g
- average length - 125 mm
- average width - 75 mm
- average depth - 82 mm
- lenticels* - small, yellow
- internal colour - yellow
- firmness - medium-firm
- pulp fibre - medium
- skin thickness - medium-thin
- pulp recovery - 73 per cent
- flavour - mild, aromatic.
* Refer to Glossary
Palmer trees are of medium-to-low vigour with an open, upright canopy. Branches have a natural tendency to grow long and thin, arching to the ground with heavy crop loads when left unpruned. Six-year-old trees are commonly 2-5 m high and 2-4 m in canopy diameter.
- panicle* length - 30+ cm
- panicle width - 15-20 cm
- panicle colour - dull red
- panicle hairs - many, pink
- colour of wilted petals - light pink
- fragrance - strong
Palmer is a monoembryonic* variety, so the seed, if planted, will not produce seedlings that produce fruit true to type and will need to be grafted onto a uniform polyembryonic* rootstock. Kensington Pride has been the most widely used rootstock in the past.
Planting densities for Palmer are generally higher than for Kensington Pride and R2E2. This variety is best planted at spacings of 4-6 m within the row and 7-9 m between rows (357-185 trees/ha). Higher densities can be used, though you will need to control tree size.
Pruning and shaping
Palmer is an open and spreading tree. When unpruned, it develops a few long arching branches that do not produce good fruit quality or high yields. You can improve tree shape by pruning and shaping in the first few years after planting. The first branching of the trunk should be high (1.2-1.5 m) to prevent fruit hanging on the ground. To force them to branch often, cut the limbs of Palmer every second growth flush. This will maximise the number of terminals and the fruit-bearing surface. Keep the lower branches short to prevent fruit hanging on the ground and reduce the need for propping. Palmer takes 4-6 years to produce an adequate bearing frame.
Flowering and fruit set
Palmer is generally a strong consistent flowerer that sets a lot of fruit. However, when temperatures are low, much of the fruit set is nubbins (fruit without a seed). These are either shed late during fruit development or held full term but only reach three-quarters the size of seeded fruit. In the Northern Territory, the flowering of Palmer is erratic, which often causes low yields.
Crop yields will vary considerably between seasons and trees. Trees of 6-8 years can produce 12-30 kg per year.
Pest and disease status
Palmer is susceptible to bacterial black spot. This disease can cause severe fruit loss if allowed to build up in trees before flowering. Other post-harvest diseases that can affect Palmer are anthracnose (Collectotrichum gloesporioides), a major cause of fruit blackening and stem end rot (Botryosphaeriaspp. and Lasiodiplodia theobromae).
Palmer is affected by major insect pests such as mango scale (Aulacaspis tubercularis), tipborer (Penicillaria jocosatrixm and Chlumetia euthysticha), fruit flies (Bactrocerasp.) and planthopper (Colgaroides acuminata).
Palmer is prone to internal disorders when grown on sandy soils. Internal breakdown appears as a small dark spot in the fruit pulp that develops a water-soaked region around it. In severe cases, the fruit pulp breaks down, leaving a blackened cavity several centimetres in diameter. Sapburn is not a significant problem in this variety.
Harvesting and handling
Palmer is a late-maturing variety with fruit ripening 4-6 weeks after Kensington Pride. In the Dry Tropics of Queensland, harvesting usually starts in early January and, in the Mareeba district, in mid-to-late January. Fruit are harvested over a 4-6 week period and three to five picks may be required to harvest the crop. The fruit turns dark purple well before it matures, so judging maturity on fruit colour alone can be deceiving.
Fruit is ready to harvest when the internal colour has changed from white to yellow, the shoulder and beak have fully filled out, and the nose of the fruit changes from a dark to lighter colour.
Palmer has export clearance for Japan after treatment with approved vapour heat treatment for fruit fly disinfestation.
Pores in the skin of the fruit
Single embryo in seed, producing a seedling that is a genetic cross between the mother tree and pollen donor
Branched flower spike with many flowers
Seed with multiple embryos, producing seedlings that are genetically identical to parent tree