Leylandii conifers, or Leyland Cypress (x Cuprocyparis leylandii), is a conifer that has become a cornerstone in British gardening, particularly for those seeking a fast-growing hedge. Known for its rapid growth rate and dense foliage, Leylandii can provide towering privacy, wind protection, and an attractive green barrier when properly maintained. This article aims to provide detailed information on planting, maintaining, and troubleshooting Leylandii hedges, ensuring they remain a valuable asset to any garden.

Types of of Leylandii conifers

Golden Leylandii

Golden Leylandii, specifically the Castlewellan Gold (x Cuprocyparis leylandii ‘Castlewellan Gold’), is the most popular variant of Leylandii with golden foliage. The vibrant golden hue adds a striking contrast to the typical green landscapes, making it a popular choice for ornamental purposes. Other varieties, like ‘Gold Rider’, are commercially available, while ‘Robinson’s Gold’ and ‘Excalibur’ are rarer but sometimes found in specialized nurseries. These golden variants grow more slowly than the standard green Leylandii but offer the same dense foliage and columnar growth habit.

Green Leylandii

Green Leylandii (x Cuprocyparis leylandii) is the fastest-growing conifer in the UK, capable of growing up to 90cm (3 feet) per year under ideal conditions. This rapid growth rate makes it the preferred choice for those looking to establish a hedge quickly. The Green Leylandii is a hybrid of the Nootka Cypress (Chamaecyparis nootkatensis) and the Monterey Cypress (Cupressus macrocarpa). This hybridization occurred when the two species were planted near each other in the UK and Ireland, resulting in a tree that combines the hardiness of both parent species.

 

Planting and Watering Leylandii conifers

Choosing the Right Time to Plant

When planting Leylandii, timing is crucial for ensuring the trees establish well. If planted between November and February, the cooler, wetter weather typically reduces the need for frequent watering. However, for container-grown Leylandii planted from March to October, consistent watering throughout the warmer months is essential to prevent the roots from drying out.

Watering Newly Planted Leylandii conifers

For the first year after planting, newly planted Leylandii need regular watering to ensure their roots establish deeply and robustly. This involves checking the moisture level of the soil around the root ball every 2-3 days during the growing season (February to October). The soil should be kept moist but not waterlogged. A good soaking once or twice a week is usually sufficient, but in hot and dry weather, more frequent watering may be required.

Using Irrigation Systems

An irrigation system like a Porous Pipe (leaky hose) is an efficient way to water Leylandii. It allows water to seep gradually into the soil, ensuring consistent moisture without the risk of waterlogging. Typically, watering with a Porous Pipe for 2-3 hours once a week should be enough, though this may need to be increased during periods of extreme heat.

Avoiding Over and Underwatering

Leylandii conifers are susceptible to both drought and waterlogging. Signs of stress due to improper watering include yellowing and browning needles, usually starting at the base of the tree. In the case of overwatering, particularly in heavy clay soils, waterlogging can cause root rot, which mimics drought symptoms. To avoid these issues, ensure the soil drains well and adjust watering according to the weather and soil conditions.

 

Establishing a Leylandii conifer Hedge

Initial Trimming and Shaping

Once Leylandii trees are planted, it is important to start trimming them to shape early. This means cutting back any branches that extend beyond the desired shape of the hedge. By trimming regularly from the outset, you encourage dense growth from within, which helps the hedge thicken and establish a robust form. When the trees approach the desired height, typically within 6 inches (15cm), trimming the tops will further promote lateral growth and density.

Ongoing Maintenance

After the initial shaping, Leylandii hedges should be trimmed at least once a year to maintain their shape and prevent them from becoming overgrown. For optimal results, trim the hedge in the spring or early summer, allowing it to recover and regrow before winter. Avoid trimming during hot, dry weather or in late autumn, as this can stress the plants and make them more susceptible to diseases and pests. Always leave at least 4 inches (10cm) of green foliage on the hedge to ensure healthy regrowth.

Dealing with Neighbours and Legal Considerations

When planting a Leylandii hedge on a boundary, it is important to consider your neighbours. Leylandii hedges can grow very tall and dense, potentially blocking light or views, which can lead to disputes. Under the Anti-social Behaviour Act (2003), UK councils can intervene if a hedge adversely affects a neighbours' enjoyment of their property. Therefore, it is wise to consult with neighbours' before planting and agree on a height that will be maintained.

 

Trimming and Maintenance

Annual Trimming Leylandii conifers

All hedges, including Leylandii conifers, require annual trimming to keep them healthy and manageable. Although some recommend trimming Leylandii up to three times a year, once or twice is generally sufficient and avoids weakening the hedge. Over-trimming, especially during times of stress like drought or extreme heat, can prevent the hedge from recovering properly and lead to increased vulnerability to pests and diseases.

Tools and Techniques

Use a sharp pair of shears or a hedge trimmer to cut back the foliage, making sure the blades are sharp to avoid tearing the branches. After trimming, clear any trimmings from the top of the hedge, as these can rot and encourage disease. Trimming is best done in a tapering shape, where the base of the hedge is slightly wider than the top, allowing light to reach all parts of the hedge and promoting even growth.

Addressing Tall Hedges

If you allow a Leylandii hedge to grow too tall, it can become difficult to manage without professional help. Hedges that reach 10-15ft (4-5m) may require specialist equipment like hedge-cutting platforms. To avoid this, maintain the hedge at a manageable height, typically around 6-8ft (2-3m), which can be trimmed easily with standard garden tools.

 

Disease and Pest Management

Common Leylandii Conifer Diseases

• Pestalotiopsis and Botrytis (Grey Mould): These fungal diseases are more likely to occur in wet conditions and can infect plants weakened by over-trimming or poor care. Symptoms include brown patches and dieback of shoot tips. To prevent these diseases, avoid over-trimming and remove dead material from within the hedge to improve airflow.

• Honey Fungus: This soil-borne fungus attacks the roots of Leylandii, leading to the death of entire plants. Symptoms include clusters of honey-colored toadstools and a strong mushroom smell from infected roots. There is no chemical treatment, so infected plants must be removed to prevent the spread of the fungus.

• Phytophthora: Another soil-borne disease, Phytophthora, causes entire plants to turn grey or brown and die. It is often found in poorly drained soils and is difficult to control once it has taken hold. Removing infected plants and improving soil drainage are essential for managing this disease.

 

Pest Control

• Cypress Aphid: Cypress aphid is a common pest that attacks Leylandii in late winter or early spring. It causes brown patches to appear in the hedge, usually in late spring. These aphids are well camouflaged and align themselves on the bark, making them difficult to spot. Early detection is key; spraying with systemic insecticides can effectively control them.

Best Practices for Leylandii Confier Care

• Trim once a year: Over-trimming weakens the hedge and increases the risk of disease and pest attacks. Trimming once a year is sufficient to maintain shape and health.
• Avoid cutting back too hard: Always leave at least 4 inches (10cm) of green growth on the hedge. Cutting back to the brown wood can prevent regrowth and lead to a sparse appearance.
• Timing is key: Trim your Leylandii hedge in the spring or early summer to allow for recovery and regrowth before winter. Avoid trimming in late autumn to reduce the risk of pest infestations.
• Monitor for pests: Regularly check your hedge for signs of Cypress aphid and other pests, particularly in the early months of the year. Prompt treatment can prevent extensive damage.
• Keep it legal: If your hedge is near a boundary, communicate with your neighbours and adhere to local regulations to avoid legal disputes.

Conclusion

Leylandii is a versatile and powerful conifer that, when properly maintained, can provide years of service as a hedge or specimen tree. Its rapid growth and dense foliage make it ideal for creating privacy and windbreaks. However, its potential for rapid growth and susceptibility to certain diseases and pests mean that proper care and regular maintenance are essential. By following best practices for planting, watering, trimming, and monitoring, you can ensure that your Leylandii hedge remains healthy, attractive, and an asset to your property for many years.