Family – ROSACEAE

Botanical Name Prunis dulcis (formerly Prunus amygdalus var dulcis)

Introduction

The humble almond can be overlooked, but is a delicious treat, and compares well with all our other nuts.

The almond is only a peach in disguise. A dry fleshed close relative of the peach, the flesh being replaced with a thin dry leathery hull.

There are wild relatives of almonds growing over Central Asia, Asia Minor and Eastern Europe. But cultivate almonds are restricted to warm climates, and mild winters. What we term Mediterranean climates. Others possibly call them hot arid regions, California, South Africa, Australia and Chile. We are relatively marginal for almonds.

Commercial growing of almonds is limited to areas where no or little frost hazard because of their early blossoming but with the renewed interest in healthy foods and because of the quantities imported it is an undeveloped crop in New Zealand. Suitable areas would be parts of Hawkes’ Bay, Nelson, Canterbury and Otago where humidity is not a problem.

Most of the almonds we use are from California.

Bitter almonds (Prunus amara) which are used for flavouring are differentiated by their white flowers with a pink base. The striking bitter edge and aroma is due to the hydrogen cyanide (cyanogenic glycosides) in the kernels. Three of these raw kernels can cause severe poisoning in children and 50-70 can cause death in adults (heating deactivates the enzyme). Oil is made from the kernels and detoxified to use in Maraschino Cherries, extracts and Amaretto Liqueur.

The test to tell the difference between sweet and bitter almonds is to crush them with water and the milky-white emulsion will smell of hydrocyanic acid if it is bitter almond, whereas the sweet almond will be free of this odour. Sweet and bitter almonds are different products and are not interchangeable.

The tree description

A small to medium sized tree up to 10m high with very dark bark cracked into small scales. Lanceolate leaves up to 12cm long have rounded teeth at the margins and are on long stalks.

Trees can grow to 6-9m tall. They are one of earliest trees to flower. Flowering looks as good as for any ornamental tree.

They flower on spurs on 2-3 year old wood and one year old laterals. The outside shell develops early but they only start to fill the nut inside in the last 2 months of the season.

The cultivated almond is sweet, not bitter like most peach seeds.

There is graft and pollen compatibility with other stone fruit. Almond, plum and peaches are all used as rootstock for different soil conditions. Some of the more modern rootstock for plums and cherries would probably suit almonds.

Climatic and soil requirements

There are wild relatives of almonds growing over Central Asia, Asia Minor and Eastern Europe. Cultivation of almonds is restricted to warm climates and mild winters. What we term Mediterranean climates. Others possibly call them hot arid regions; California, South Africa, Australia and Chile. We are relatively marginal for almonds.

Almonds are hardy to –7°C, but actually seem hardier than this in New Zealand. They need winter chilling of 300-600hrs below 7°C (depending on cultivar) to break dormancy and mature the buds. The blossoms and young fruit can be killed by –1°C degree frost, but this is probably also not so in New Zealand as I am sure it is colder than this sometimes in Marlborough. A sloping ground can aid in frost protection. Buds can tolerate more frost than open flowers.

Trees need 180-240 growing days to mature the crop. There is the need for mild weather over flowering so the bees can work.

Rainfall of below 500mm per year is usually supplemented by irrigation needed in the ideal dry climates. Wet conditions may encourage fungus problems especially rainy weather in spring and summer. Shelter from high winds.

Almonds produce better on light types of soil, as their roots don’t tolerate wet soils. Well drained loamy soils are best with pH 6-7.

Flowering & Pollination

Bud burst ranges from late July to early September depending on season and cultivar. Laterally on shoots produced the previous season – perfect flowers? They flower before any current season’s growth is made. One or several flower buds can form on a single spur.

Flowers appear a long time before the leaves in young specimens and slightly before them on mature trees. They are white tinged with pink and can be 5 cm across with a reddish calyx and borne singly or in pairs on short stalks.

There are usually far more flowers than is needed for a good crop. But a heavy crop does not cause biennial bearing as with many other crops.

The almond flower has a single pistil with two ovules. One or both of which may develop into fruit but a single nut is desired commercially. The ovary is in the green bracts with 5 petals and 10-30 stamens. Honey bees collect both pollen and nectar but the quality of honey is not very good. The flower is most receptive to cross pollination the day after opening and decreases receptivity the next 4-5 days. Flowers not pollinated fall off in about a month.

Almonds can be self-sterile and some are cross-incompatible as well so it is important to select the right varieties in the right proportion.

They are generally self-sterile, so need a pollinator. These have to be specific, as there is incompatibility between varieties. There is a character called Xenia in almonds that means a sweet almond crossed with a bitter one. This means you will have bitter almonds. You must have sweet by sweet.

The climate needs to be suitable for the bees at flowering time. Pollinators need to be planted close enough to enable the insects to work the trees taking into account the differences in times of blooming. You will need at least two varieties, preferably three or four with overlapping flowering times. This allows for vagaries in the season and allows for pollination even if some are early or late.

Not all flowers set fruit and bees must visit some several times on the one tree as well as other cultivars. Most pollination is done around midday as the weather is more settles then and low temperatures are also restricting to bee activity. Theoretically though only one grain of pollen is necessary it must be compatible and at the right time. Adjoining sources of nectar and pollen can affect forager effectiveness so don’t have another crop nearby which bees could use as a food source.

A profitable crop depends on cross pollination of most flowers as fruit is not thinned.

Propagation

Rootstocks are peach which is used for precocity or plum for wet feet conditions. Suitable cultivars are propagated by budding.

Planting & Training

For good results plant singles rows of cultivar with pollinators either side for easier harvest as they mature in sequence and better use can be made of machinery and facilities.

Plant trees in late winter to early spring depending on soil conditions. Usually spacings of 6 x 6 m between and within rows are used though some closer hedgerow plantings have been tried.

They can be finicky trees. Sometimes they stay dormant for a season before growing. Select four main branches 10-15cm apart to train to an open vase shape. These main branches are further allowed to have three extra sub-branches. Pruning can be every 2-3 years.

In general almonds are pruned lighter than peach trees as more fruiting wood is necessary for a crop. Because of this lighter pruning almond trees tend to become large with long branches. Larger and few cuts are made on almonds compared to peaches. Long laterals and water shoots are a sign of over pruning.

Trees can be top-grafted to other cultivars if the ones you have are not satisfactory.

Irrigation

Although they are drought resistant, the nuts will be small if subject to severe conditions early in the season. You will get large empty nuts if very dry at the end of the season.

Fertiliser

1-2kg of NPK 9:4:5 per tree is usually sufficient, but apply extra Nitrogen if growth is poor.

Nuts

The yellowish-green fruits are downy oval drupes, slightly furrowed along one side. The shell contains one or two edible seeds surrounded by a thin cinnamon coloured skin containing prussic acid which gives them their characteristic flavour.

They are used for Marzipan.

Harvesting

Nuts mature in early autumn (March/April) when the hull begins to dry and shrivel, then splits to reveal the shell. They are then either hand picked or mechanical shakers can be used to remove the nuts from the tree. They are then run through a hulling machine.

Nuts can be air dried over a relatively long time as they don’t seem to deteriorate. Mechanical dryers would be used for commercial growers. Delaying harvest is not too detrimental to quality.

Yield

It is possible to get 4.5 tonnes/ha, but this is not usual. Inshell 1700kg. Trees start bearing in year 3 or 4, and reach full production in year eight. Production can go on for 50 years.

Types

There are three categories: hard shell, soft shell and paper shell

‘Paper shell’ almonds have a nut that is so soft it can be rubbed off by hand.

These are desirable from the user friendliness point of view, but are more likely to be damaged by insects, or even birds.

‘Soft shell’ are easily opened with a kitchen nut cracker

‘Hard shell’ have a shell as hard as a peach stone, or harder.

Cultivars

402 (NZ ex Blenheim – similar Chellaston, South Australia)

Soft-shell locally selected variety. The nut is ready about mid autumn. In humid climates, the fleshy fruit tends to become diseased, and shrink onto the nut shell making it a bit difficult to remove. The kernel is large, acutely pointed, somewhat flat. Neither bitter nor sweet, its flavor is unremarkable. Not a particularly productive tree.

403 (NZ ex Blenheim- similar Jordan Rock, Spain)

Large, soft shelled, early and prolific bearer with sweet, mild flavoured nuts. Keel not prominent. Suitable dry climates only. Long flowering period (4 weeks) makes it a good pollinator especially for Fabrin. Nuts fall April

All-in-one (US, NZ)

Soft-shell, fat, large kernels, sweet and flavorful. Showy white flowers bloom late. Production is very low in humid areas due to a disease shriveling the kernel. Semi-dwarf tree. Self-fertile

Burbank

Soft shell, sweet mild flavour. Heavy cropper. Not suitable humid areas. Self-sterile

CY750

Paper shell. Large nut with good flavour

Fabrin (NZ ex Manawatu – probably seedling IXL)

Medium to soft shell, mild flavour, prolific. Suitable dry climates only. Flowers early September (white petals, red calyx) and nuts fall April. Possum resistant. Pollinator is 403

Garden Prince

Soft shell, well sealed, medium sized, sweet and tasty, dwarf type. Good for containers. Blooms early. Self-fertile

IXL (NZ, US)

Soft shell with large nuts usually with single kernel. Consistent cropper. Not always well-sealed and so not suitable humid areas. Hulls easily so no machine needed. Ripens mid autumn. Tree sturdy rather upright grower with large leaves. Pollinates with Ne Plus Ultra. Shy bearing but desirable in some areas. Susceptible to “blast” in some areas. Self-sterile.

Monavale (NZ)

Hard shell, strong flavoured kernel, heavy cropper, good pollinator. Will flower and crop regularly in most places in NZ. Best in hot dry areas. Nuts ready March/April. Self-fertile

Nonpareil

Paper shell, smooth medium-large size, sweet flavour, flat attractive nut. Main variety California. Large trees which harvest easily but must be harvested quickly once mature as often poorly sealed. Shelling percentage 60-70

Ne Plus Ultra

Soft-shell, large flat nut, poor quality with numbers of doubles, early blooming – about a week ahead of Nonpareil so subject frost damage. Low chill. Nuts drop.

‘Nonpareil’ is planted more than any other cultivar and accounts for more than half of the almond production in the USA. The ‘Kapareil’, developed and deriving its name from the ‘Eureka’ and the ‘Nonpareil’, is a good pollinator for the ‘Nonpareil’ (Kester et al. 1963).

The ‘Texas’ or ‘Texas Prolific’ is the second most important cultivar. It shells only 40 to 45 percent meat, blooms several days to 1 week after ‘Nonpareil,’.

Other varieties that I am not sure of are: Texas (Mission), Drake and new varieties: Kapareil and Davey.

Note: Nonpareil and IXL are not compatible.

Nutrition

50% fat, 67% oleic and 24% linoleic unsaturated fat. Also carbohydrate, protein and a range of minerals.

Diseases

Are as for other stonefruit. Bordeaux is a good all round chemical still for stonefruit.

Compiled by Roy Hart, 2001

Additional information Gail Newcomb, October, 2002
Privacy removals and proprietory format conversion – December 2007

This fact sheet has been produced with the latest information available at the time of publication. In no way, however, can this sheet be considered the ultimate in information for New Zealand growing conditions: it is just a basic guide on the subject. If any member has information to add, or feels that any of the information is misleading, then we ask you to comment as appropriate.