Hollong (Dipterocarpus retusus)

Hollong (Dipterocarpus retusus)

Local Indian Name:

• Assamese: হলং (Hollong)

• Bengali: হলং (Hollong)

• Hindi: होलोंग (Hollong)

Scientific Name: Dipterocarpus retusus

Family: Dipterocarpaceae

Category and Subcategory:

• Category: Evergreen Tree

• Subcategory: Timber and Ecological Tree

Native Region:

• Indigenous to India, Myanmar, Thailand, Laos, and Southern China.

• Found mainly in Northeast India, particularly in Assam, Arunachal Pradesh, Nagaland, and Meghalaya.

Introduction

Hollong (Dipterocarpus retusus) is a state tree of Assam and a significant species in the dense rainforests of Northeast India. It is a tall, straight tree known for its high-quality timber and role in ecosystem balance. Due to its fast growth and economic importance, it is widely cultivated for afforestation and timber production.

Importance & Benefits

Environmental Importance:

• Soil Conservation: Prevents erosion with its deep root system.

• Carbon Sequestration: Absorbs significant amounts of CO₂, helping mitigate climate change.

• Habitat Provider: Serves as a shelter for various wildlife species.

Economic Importance:

• Timber Production: High-quality wood used in construction and furniture making.

• Resin Extraction: Resin is valuable for varnish, paints, and waterproofing.

Medicinal Uses:

• Resin extracts are used in Ayurveda for treating skin ailments and wounds.

Description and Cultivation

Botanical Description:

• Height: Grows up to 40-50 meters tall.

• Trunk: Straight with cylindrical shape, reddish-brown bark.

• Leaves: Large, elongated, and leathery with prominent veins.

• Flowers: Pink to purple bell-shaped flowers bloom in clusters.

• Fruits: Winged seeds (samara) that aid in wind dispersal.

Major Growing Regions in India:

• Found in Assam, Arunachal Pradesh, Meghalaya, and Tripura.

Varieties and Cultivars

There are no officially classified varieties, but regional variations exist due to environmental factors.

Location and Light

• Climate: Thrives in humid, tropical, and subtropical climates.

• Sunlight: Requires full sun exposure for optimal growth.

• Altitude: Found at elevations between 50–1000 meters.

Soil Preparation

• Type: Prefers deep, well-drained loamy or lateritic soils.

• pH Range: 5.5 to 7.0 (slightly acidic to neutral).

• Nutrient Enrichment: Organic matter like compost or manure improves soil fertility.

Planting

• Propagation: Grown from seeds or saplings.

• Planting Season: Best planted during the monsoon season (June-August).

• Spacing: Maintain a gap of 5-6 meters between trees to allow healthy growth.

Watering

• Young Plants: Require regular watering for the first 2-3 years.

• Mature Trees: Drought-resistant but benefit from occasional deep watering.

Pruning

• Purpose: Removes dead, weak, or pest-infected branches to enhance timber quality.

• Timing: Best done after the monsoon season.

Pest and Disease Management

Common Pests:

• Bark Borers: Insects that damage the tree trunk.

• Leaf Miners: Cause leaf discoloration and reduced growth.

Common Diseases:

• Fungal Rot: Affects roots and trunk in waterlogged areas.

• Leaf Spot Disease: Leads to premature leaf drop.

Management Practices:

• Organic: Use neem oil and biopesticides.

• Chemical: Apply eco-friendly fungicides when necessary.

• Preventive: Maintain proper spacing and remove infected parts.

Environmental Conditions

• Temperature Range: Thrives in 22°C to 35°C.

• Rainfall: Requires 2000-4000 mm of annual rainfall.

• Humidity: Prefers high humidity levels.

Propagation

• Seeds: Collected during the dry season and directly sown or grown in nurseries.

• Saplings: Transplanted after 1-2 years of nursery growth.

Uses

Timber Industry:

• Used for furniture, plywood, doors, and construction.

• High demand for boat building due to its water-resistant properties.

Resin and Oil Extraction:

• Resin is used in paints, varnishes, and waterproofing compounds.

Traditional and Cultural Uses:

• Considered sacred among indigenous communities in Assam and Arunachal Pradesh.

Monetary Benefits

• Timber Value: High market price due to its durability and strength.

• Resin Production: Generates additional income for farmers.

• Afforestation Projects: Government and private sectors invest in Hollong plantations for sustainable timber.

References:

1. Indian Council of Forestry Research and Education (ICFRE) Reports

2. Assam Forest Department Publications

3. Agricultural University Studies on Dipterocarpus retusus

4. Traditional Knowledge from Indigenous Communities of Northeast India