Germination temperature
Cool Himalayan monsoon conditions: acorns germinate as soon as they fall in summer, and seedlings emerge in July-August.
Tree growing guide
Kharsu oak is the high-altitude Himalayan oak of the timberline, and its acorns must be sown fresh because they die if they dry out. This guide covers handling the acorns, nursery sowing in the monsoon and planting out at altitude.
Cool Himalayan monsoon conditions: acorns germinate as soon as they fall in summer, and seedlings emerge in July-August.
About 2 cm (0.8 in), in nursery lines 20 cm (8 in) apart.
Immediate: the root (radicle) emerges soon after the acorn is shed.
Seedlings need abundant overhead light; they do not establish in shade.
None. Acorns are recalcitrant: sow fresh and never let them dry.
Both: direct sowing gives the best trees; nursery stock is planted out at two years with a ball of earth.
Acorns take about 15 months from flowering to ripen and mature in June-August; ripe acorns turn black. Pick them from the tree, because acorns from the forest floor are often insect-damaged. Fresh acorns are 95-100% viable, and about 140 weigh 1 kg. Choose the biggest: in a Central Himalayan study large acorns germinated best and gave seedlings with about 31% more dry mass than medium ones.
Not needed. The acorn shell does not block germination.
Not needed. Kharsu acorns have no dormancy and start to root almost as soon as they fall.
Not needed if acorns are fresh. The real rule is never to let them dry: World Agroforestry warns that the species quickly loses viability if allowed to dry out. Acorns can be held moist and cool for a short time, but sowing immediately is best.
Sow during the monsoon in the cool climate of the oak's own zone, 2,100-3,800 m in the Himalaya. It is a timberline tree and is not suited to the hot Indian plains.
About 2 cm (0.8 in) deep in lines 20 cm (8 in) apart, as practised in Indian forest nurseries. Lay acorns on their side if a root has already appeared, and cover gently.
Deep, rich, moist loam. World Agroforestry notes the best growth on deep clayey loam; the tree survives on rocky ridges but stays stunted there. Deep bags also work for nursery plants.
Keep beds moist and weeded. Protect them from mice and squirrels, which dig out and eat acorns.
Give open, sunny beds. Natural regeneration needs abundant overhead light, and canopy gaps with exposed soil favour seedlings.
The radicle appears within days of the acorn falling; the shoot follows later, with seedlings emerging in July-August. In a Himalayan field study acorns left to sprout on the ground produced only about 20% seedlings, while acorns sown once the swollen radicle was 10-15 cm (4-6 in) long and 2-3 cm thick gave about 80%. Handle sprouted acorns carefully and never snap off the thick root.
In the summer after sowing, thin nursery seedlings to about 10 cm (4 in) apart. Plant out two-year-old seedlings with a ball of earth in July-August, at about 2.5 x 2.5 m (8 x 8 ft). World Agroforestry reports that winter planting fails and that seedlings should not stay in nursery beds longer than two growing seasons.
Keep young plants free of weeds, thick grass and heavy leaf litter, all of which hold back regeneration. Fence out grazing animals: browsing and trampling are a major reason kharsu fails to regenerate.
Cause: they dried out in storage or transit; recalcitrant seed dies when dry. Fix: sow on arrival and keep any waiting acorns cool and moist.
Cause: insect damage, common in acorns picked up from the ground. Fix: collect ripe acorns from the tree and discard damaged ones.
Cause: mice, squirrels, birds and monkeys eat the acorns. Fix: cover beds with mesh until seedlings are established.
Cause: planting in the dormant season, which fails for this species. Fix: plant out in July-August with an intact root ball.
Cause: too much shade, thick litter or grass. Fix: plant in canopy gaps or open ground with abundant overhead light.
Its main belt is about 2,400-3,800 m, occasionally down to about 2,000 m on cool northern slopes. Lower and warmer gardens are unlikely to suit it.
Heavy seeding comes every second or third year; one 12-year record had four abundant years and eight poor to moderate ones.
Direct sowing in weeded lines has worked in India and tends to give the best trees.
Kharsu coppices and pollards fairly well and is lopped for fodder on a 3-4 year cycle in parts of the western Himalaya.
Sow kharsu oak acorns as soon as they arrive to raise the hardy timberline oak of the Himalaya.
Only briefly and only moist and cool. The acorns are recalcitrant and lose viability quickly once they dry, so sowing straight away is best.
No. Kharsu acorns root almost as soon as they ripen. Sow them carefully without breaking the thick root; in one study such sprouted acorns gave about 80% seedlings.
It is not suited to them. It is a high-altitude Himalayan oak growing mostly between about 2,100 and 3,800 m.
In the monsoon, July-August, as two-year-old plants with a ball of earth. Winter planting fails.