Almond

About

An almond will grow perfectly well in a cool maritime climate and will hardly ever give you almonds. The tree is hardy enough, but it flowers in February, which is a month with frost in it and almost no flying insects, and a crop needs both to be absent and present respectively.

That leaves most almond trees in cool climates as ornamentals, and they are lovely ones. Pink-white blossom on bare black wood in late winter is worth the space on its own, and it comes weeks before anything else in the garden.

If you want nuts, the answer is a fan against a warm south wall, a variety chosen for self-fertility, a paintbrush for hand pollination, and fleece over the blossom on frosty nights. That combination works at the mild end of a maritime climate and is optimistic beyond it.

The other thing to know is peach leaf curl. Almond is in the same group as peach and gets it just as badly.

Appearance and character

A small deciduous tree, 4 to 8 m free-standing, with an open habit and ascending branches. Fan-trained against a wall it holds at about 2 m.

Bark is dark grey and smooth on young wood, cracking into small plates with age.

Leaves are long, narrow and finely toothed, 6 to 12 cm, glossy mid-green, appearing after the flowers.

Flowers open on bare wood in February and early March, 3 to 5 cm across, white to pale pink with darker pink at the base, five petals, borne singly or in pairs.

Fruit is a drupe, and the part everyone calls the nut is the seed inside the stone. The outer flesh is a thin grey-green leathery hull that splits along one side as it dries.

‘Robijn’ and ‘Ingrid’ are partially self-fertile and the sensible choices where the season is short. ‘Mandaline’ is another. Ornamental almonds are grown for blossom and crop poorly.

Where it is from

The almond is native to western and central Asia, and the wild ancestor is a bitter-kernelled tree of dry stony hillsides.

Domestication turned on a single mutation that switched off amygdalin production in the kernel, and every sweet almond descends from that change. It is one of the oldest deliberate selections in agriculture, dating back at least five thousand years.

It spread through the Mediterranean early and is mentioned throughout the Bible and in Greek and Roman writing.

The Romans brought it to Britain, where it has been grown for blossom rather than crop ever since, because the climate has never suited the fruit.

California now grows most of the world’s almonds, and the crop there depends on the largest managed pollination event on earth, with hives trucked in from across the continent each February.

How it grows

Buy a grafted tree on St Julien A rootstock for a fan, or Krymsk for a smaller tree. Seedling almonds may carry bitter kernels and should not be grown for eating.

Plant between November and March against a south or south-west facing wall in the warmest, most sheltered spot you have.

Free-draining soil is not negotiable. Almond dies on wet ground faster than almost any other fruit tree.

Space a fan at 4 m of wall and a free-standing tree at 6 m.

Train as a fan. Wall protection buys warmth for the blossom, shelter from rain that spreads leaf curl, and the option of covering the tree.

Cover from January to May with a polythene or clear plastic shelter open at the sides. This keeps rain off the buds and is the single most effective measure against peach leaf curl.

Hand pollinate. Move pollen between flowers with a soft brush in the middle of a mild day, and repeat every day or two while the blossom lasts. In February there are almost no bees.

Fleece the blossom whenever frost is forecast.

Harvest in September and October when the hulls split and start to dry. Remove the hull, dry the stones in an airy place for a week or two, then crack.

Through the seasons

Midwinter is for planting, for winter pruning if it must happen, and for getting the rain shelter up before the buds move. Aim for the end of January.

February and March are blossom, hand pollination and frost watch. Fleece on cold nights and pollinate on mild days.

Spring brings the leaves, and with them any leaf curl that got through. Pick off blistered leaves as they appear.

Summer swells the nuts. Water weekly and prune in dry summer weather rather than winter, which is the rule for all stone fruit.

Autumn is the harvest, from September, when the hulls split. Dry the stones thoroughly before storing.

Care difficulty

Difficult, and the difficulty is the calendar rather than the culture.

February blossom is the root of it. Frost kills the flowers outright, and even in a mild spell there are few pollinating insects about, so a full crop needs both luck and a paintbrush.

Peach leaf curl is the second problem and it is entirely predictable. Spores land in rain on swelling buds in late winter, and leaves emerge thickened, blistered and red before dropping. Keeping rain off the tree from January to May prevents it.

Drainage is the third. Almond will not tolerate winter wet and dies of root problems on heavy ground.

Bacterial canker and brown rot follow on stressed trees, particularly those pruned in winter.

None of this applies if you are growing the tree for blossom, in which case it is an easy and reliable small tree.

Watering

Water weekly through summer while nuts are swelling, around 20 litres for an established fan.

Water at the base and never over the foliage. Wet leaves spread leaf curl and brown rot.

A wall-trained tree needs more water than a free-standing one, because the wall keeps rain off the root run all year, not just in the months you want it to.

Mulch in late winter with compost over the root spread, kept off the trunk.

Reduce watering from September once the hulls begin to split, since wet at harvest spoils the kernels.

Never let the tree stand in wet soil over winter.

Warning signs, diseases and pests

Peach leaf curl produces thickened, puckered, red and white blistered leaves in spring, which then drop. It rarely kills a tree and it costs a year’s growth and crop. Shelter the tree from rain between January and May, remove affected leaves, and rake up fallen ones.

Frost-blackened blossom in February is the commonest cause of no crop. Fleece whenever a frost is forecast.

Blossom wilt browns the flowers and the spur behind them, and brown rot follows on the fruit with buff rings of pustules. Remove mummified fruit and affected spurs.

Bacterial canker sinks patches of bark with amber gum oozing from the edge, and kills branches. Prune only in dry summer weather, and cut well into clean wood.

Aphids curl the young shoot tips in spring and are usually controlled by predators.

No nuts despite good blossom usually means no pollination rather than any disease.

Empty or shrivelled kernels at harvest mean drought during the summer.

Growing environment

Full sun, and in a cool climate that means a south or south-west wall for a crop.

Deep, light, free-draining soil. Sandy loam is ideal and heavy clay is fatal.

Around pH 6.5 to 7.5, and it tolerates chalk better than most stone fruit.

Shelter from cold wind, which matters at flowering more than at any other time.

Avoid frost pockets absolutely. A tree that flowers in February cannot afford cold air pooling around it.

The warmer and drier the position, the better. Almond originates on dry stony hillsides and a hot dry summer is what ripens the crop.

Feeding

Almond needs modest feeding and suffers from too much nitrogen.

Mulch in late winter with well-rotted compost over the root spread, clear of the trunk.

Apply sulphate of potash at 20 g per square metre in February. Potash firms the wood, improves flowering and helps resist canker.

Avoid high-nitrogen feeds, which produce soft growth that canker and aphids exploit and delay ripening.

A wall-trained tree in a border benefits from a balanced spring feed, since the wall keeps rain and therefore nutrients off the root run.

Nothing further is needed on reasonable ground.

Troubleshooting

Masses of blossom and no nuts. Almost always pollination. Almond flowers in February when nothing is flying. Hand pollinate with a soft brush on mild days, and choose a partially self-fertile variety.

The blossom went brown overnight. Frost. Fleece the tree whenever a frost is forecast during flowering.

The leaves are thick, puckered and red. Peach leaf curl. Keep rain off the tree from January to May with an open-sided shelter, and remove affected leaves.

Gum is oozing from the trunk. Bacterial canker, or gummosis from stress. Prune only in dry summer weather, cut into clean wood, and check drainage.

The tree died over its first winter. Almost certainly wet roots. Almond needs sharp drainage and will not survive standing water.

The kernels taste intensely bitter. That is a bitter-kernelled tree, most likely a seedling. Do not eat them. Bitter almonds contain amygdalin at levels that cause cyanide poisoning.

Can I grow one from a supermarket almond? No. Those are usually pasteurised and will not germinate, and a seedling may carry bitter kernels in any case.

Do I need two trees? Most almonds need a pollination partner. Choose ‘Robijn’ or ‘Ingrid’ if you have room for only one, and hand pollinate regardless.