Leyland cypresses (Cupressocyparis x leylandii) are hugely popular evergreen landscape trees, well known for their lightning-fast growth, low maintenance requirements, and their adaptability to a really wide range of climates and soil types. With growth rates of 3-4 feet per year and a dense and narrow growth habit, Leylands are a first pick for quickly establishing privacy screens and windbreaks. Plus, their soft, feathery foliage, year-round deep green color, and classic Christmas tree form also make Leylands an attractive focal point or landscape backdrop that can instantly transform an empty backyard space into an outdoor oasis.
When their basic requirements are met, these fast-growing evergreen beauties are relatively easy to grow and keep healthy – but in some situations, Leylands can be prone to a number of problems that can mangle their appearance and even threaten their survivability. Learn more in this article about things you can do to
- Keep your Leylands healthy, green and beautiful
- Ward off potential health issues before they become big problems later
- Recognize and treat conditions that you may be finding in your trees.
Before we dive in, let’s start with a little back story about Leylands and how they came to be one of America’s most popular landscape trees.
Often knowing where a tree comes from can help you understand some specific things that it might need to grow in its present location. This is especially true with Leyland cypress trees - which are a hybrid cross between two North American Pacific Region conifers, the Monterey cypress (Hesperocyparis macrocarpa) and the Alaska cedar (Callitropsis nootkatensis).
Though closely related, these two species originated in two separate and distinct areas of the Pacific Coastal Region with different climates. The Monterey cypress is home to the windswept rocky outcrops on the coast of central California, whereas the Alaska cedar naturally grows high in the coastal mountain forests further north in the Pacific Northwest. Specimens of these two trees were planted close together on the grounds of Leighton Hall, an English estate owned by Christopher Leyland – and in 1888 these trees crossbred accidentally. Their offspring became the Leyland cypress trees that we know today.
The combined traits of both parents make Leylands an attractive fast growing evergreen capable of growing in a wide range of climate zones and regional conditions. These trees are especially notable for winter hardiness, salt tolerance, and a capability to thrive in a diversity of soil types and climates, which in general make them fantastic low maintenance trees for the average suburban yard. However, their lineage and origin also present a few drawbacks, and Leylands are often noted for a few health issues frequently encountered in the hot and humid summer conditions of a typical residential landscape. They also have shallow root systems that make them intolerant of flooding and compacted soil. Thankfully, many of these problems can be avoided – or remedied - if attention is given to providing these trees with a little TLC to meet their needs.
With that in mind, here are some tips to keep your Leylands happy, healthy, and staying green and gorgeous.
Soil Care is really important.
Leylands are well known and appreciated for their wide tolerance to heat and cold, but true to their Pacific Northwest origins, they do best when their roots are kept moist and cool. This is becoming an increasing challenge as our summer climates are becoming hotter and drier. And as noted above, the root systems of Leylands also tend to be very shallow which makes it difficult for them to handle soil compaction, a problem that is very common in backyards that see a lot of turf mowing. They are also very intolerant to flooding in areas that tend to drain poorly. While these may seem like daunting challenges to fix, there are a few things you can do that will make a big difference:
1. Rebuild your soil’s structure with Monster’s Soil Health Program. Regardless of soil type - whether a soil is a sandy loam or a heavy clay – healthy soil is built with sufficient pore spaces that make it able to infiltrate and retain water, as well as allow some room for oxygen and gas exchange. Mimicking the cycles of nature, the Soil Health Program applies nature-based materials that incorporate organic matter deep into soil. These materials also stimulate biological activity that creates soil aggregates and pore spaces in soils, restoring an optimal balance of water and air needed to keep tree roots healthy.
2. A Soil Health Program also keeps your soil biologically active. Maintaining biological activity continually promotes a soil’s ability to retain moisture for the long term. On an ongoing basis, soil biology also cycles organic and mineral materials into just the right amounts of soil nutrients needed to optimize the health and proper growth of Leylands.
3. Avoid fertilizers, especially synthetic formulations. Leyland cypress trees prefer leaner soils and often experience health and disease issues as a result of overfertilization. Synthetic fertilizers may also deter biological activity, adversely affecting soil structure and its ability to retain moisture.
Hygroscopic humectants are a game changer in soil moisture management - which can be a huge asset for your Leyland cypress trees.
Monster Tree’s Soil Health Program also includes a bio-based soil additive – a product known as a hygroscopic humectant - that gives your Leylands a game changing advantage in searing summer heat and humidity. These amazing additives draw humidity out of the air and into your trees' soil, converting it into soil available water, helping your Leyland trees access the hydration they need on an ongoing basis.
Proper mulching can make a big difference.
A 2-3-inch-thick layer of organic mulch can offer a huge health boost to your trees and help keep them moist and cool during the summer heat. In addition to adding health benefits, mulches also add aesthetic appeal to your landscape. Organic mulches made of natural materials – especially wood chips – have several valuable benefits for your trees:
1. They help keep roots cool and prevent soil from drying out.
2. They break down over time and contribute valuable organic matter to the tree’s soil.
3. They naturally block out weeds.
4. They protect tree trunks from weed trimmer damage and shield soil from compaction caused by heavy lawn equipment.
Avoid putting down landscape fabric around the root zones of your trees.
The fabric may actually clog and become a barrier preventing water from reaching the tree’s roots. Fabric and plastic weed barriers wrapped around tree trunks can also cause problems, constricting the trunk and harboring diseases that could infect the tree.
Be careful with tree irrigations systems.
Supplemental irrigation systems can help Leylands get through long summer drought periods, but care should be taken in how these are installed around your trees and how water is being distributed. Remember that while Leyland trees like moist soil, they are intolerant of waterlogging. When implementing a watering system, make sure that your soil is adequately draining and that too much water is not flooding the roots of your trees. There are also a number of other things to look out for when installing a watering system:
1. Drip irrigation is best as long as lines are kept away from the bases of your trees. Watering lines and hoses should not be wrapped around tree trunks.
2. Avoid above ground sprinklers that spray onto the foliage or bark of your trees. Water sprayed and dripping off of foliage and tree bark can spread fungal pathogens causing diseases, and the water likely won’t reach the roots where it is needed.
3. Deep infrequent watering a few times a week is preferable to shallow watering every day, provided that there is adequate soil drainage and waterlogging does not occur.
4. Check for soil compaction around your trees to make sure that your irrigation systems are getting enough water to your tree roots – and that water is not ponding on the soil surface.
Leyland diseases to look out for
Leyland cypress trees are susceptible to a few diseases, which can affect their appearance as well as spread and threaten other Leyland trees. When caught early, Leyland diseases often can be treated or reversed. Here are some signs and symptoms to look out for.
- Seiridium (Cypress) Canker
This is a fungal disease usually identified by reddish brown drooping or flagging branches that appear in the middle of normal green branches. The fungus produces cankers that spread and girdle other branches, causing dieback that can eventually kill the entire tree. This disease is common in hot and humid conditions when there is very little soil moisture.
- Passalora Needle Blight
This is a fungal disease that affects older needles on cypress trees, causing browning in the bottom of the tree and working its way upward. Passalora commonly occurs on trees where above ground foliage has been watered, and it is often worsened in drought conditions.
- Phomopsis Twig Blight
This is another fungal disease that attacks new growth on branches, usually causing browning and dieback of new shoot tips. Progressive dieback follows, which may eventually kill an entire branch. This disease especially threatens young trees.
- Phytophthora Root Rot:
This is a root rotting disease that primarily affects trees planted in water-logged soils with poor drainage. This is a serious disease that causes trees to become stunted, with sparse growth that changes color to yellow, purple, and tan. Trees with Phytopthora usually die very quickly.
While there are treatment options for many Leyland cypress diseases, prevention is usually the best way to keep your Leyland trees healthy.
Talk to your Monster arborist about Plant Health Care options that are best suited for your Leyland cypress trees and your property. With some TLC – Tree Loving Care – your Leylands will be tall, green, and gorgeous, making your yard the outdoor retreat you have always dreamed of.