What Time of Year is Best to Prune a Conifer Tree?

Once in summer and autumn

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Expert insight into the best time for conifer tree pruning; why you should prune a conifer tree, and how to identify common conifer tree diseases.

Conifer trees are mostly evergreen and are well known for growing rapidly to soaring heights, sometimes up to 100 metres, although there are a number of dwarf, or rather, slow-growing varieties.

Of the Latin Pinophyta, there are many different types of conifer including yew, pine, Leyland cypress and Douglas fir. If you have any type of conifer on your land, either as a hedge or just a single tree, you will need to engage in regular pruning if you wish to prevent your tree or trees from growing too large for their site. The question is, when is the best time to do it, and what should you be looking out for?

Why prune a conifer tree?

Contrary to popular belief, the conifer tree requires very little pruning as it tends to maintain its shape very well. However, many people do like to undertake regular pruning of their conifer trees in order to prevent them outgrowing their sites. Even dwarf conifers will in time become large; their name is deceptive and does not mean that they will only grow to a limited height.

In actual fact the dwarf conifer is simply a slow growing variety, so whilst it will take longer than a regular conifer, it still has the potential to reach soaring heights. This is precisely why regular trimming and pruning of all types of conifer trees is important.

If you are seeking to maintain your conifers at a certain height for aesthetic purposes and have planted a dwarf variety, for this reason, you may in time wish to replace them when they start to grow above your desired height.

Another reason for regularly pruning a conifer tree is to promote good light and air flow which will ensure the base of the tree does not turn brown or become bare.

When is the best time for conifer tree pruning?

If you have a yew tree then pruning should take place twice per year, once in summer and once in autumn.

The Lawson Cypress should again be pruned twice per year, once in spring and once in summer. Thuja plicata conifers (western red cedar) should be pruned in spring and early autumn.

Never trim any type of conifer hedge after August though, as this can lead to the development of bare patches. Also be sure to avoid trimming during spells of hot and dry weather, as this could lead to browning of the leaves.

The Leyland cypress, the subject of much bad press due to the soaring heights it can reach, should be pruned between April and the end of August and it will withstand up to three cuts during the growing season once it is established.

If you have a Leyland cypress on your land, you should be aware of the Anti-Social Behaviour Act 2003: Part 8. If a hedge (defined as a line of 2 or more predominantly evergreen trees) grows to more than 2 metres tall, then it will be classed as a ‘high hedge’ which will be governed by legislation designed to protect people from nuisance. There is more information about nuisance and overgrown hedges here.

Care to take when pruning a conifer tree

Whilst some conifers, such as yew, can withstand hard pruning, you must take care not to prune into old wood for most varieties as the tree will not regrow. Instead, you should be looking only to trim the green foliage to a mossy finish, taking care not to prune into the brown wood.

Always check for birds’ nests before undertaking pruning. Under the Wildlife & Countryside Act 1981, it is an offence to damage or destroy the nest of any wild bird whilst it is being built or is in use. The bird nesting season tends to run from 1 March through to 31 July although this can vary.

What to look for when pruning a conifer tree

If you spot brown leaves on your conifer tree, this could be down to pests or diseases, although it could be incorrect or poorly timed trimming, or even because of certain growing conditions. Brown patches are a particular problem for the Leyland cypress, the Lawson cypress and Thuja plicata.

Pests that can cause brown patches include the cypress aphid and scale insects such as the juniper scale.

You should also look out for Pestalotiopsis, a fungus that causes dieback and brown patches, mostly during wet summers. If this is a problem then you will see black fruiting bodies on the leaves. Coryneum canker will also cause branch dieback in larger sized Leyland cypress and Thuja trees. Honey fungus and Phytophthora root rot will show themselves as browning pretty much throughout the tree and may result in the death of the tree.

Tree Preservation Orders

Never proceed with any tree work such as conifer tree pruning without first finding out whether there is a Tree Preservation Order (TPO) in place. If there is then permission must be gained for the works which can take up to eight weeks to materialise. Also, if the tree is located in a conservation area, permission must be obtained before commencing works of any nature.

The importance of Conifer tree pruning expertise

Due to the expansive height of the conifer tree, you are best advised to call in professional assistance when pruning any type of conifer tree. Working at height will be something they are trained and qualified in, and they will also have the knowledge to ensure the pruning is carried out correctly and at the right time of year, which is vital. Remember, overdoing the pruning of a conifer tree will lead to bear patches and incorrect timing could lead to browning of the leaves and sometimes the death of the tree.

A qualified arborist will also be able to spot signs of pest infestations or disease so that early action can be taken to preserve the health of the tree.

If you have a conifer tree or hedge on your land that needs pruning, why not contact T.H. Tree Services? As fully qualified and comprehensively experienced tree surgeons, we are able to offer specialist knowledge and skill in all aspects of conifer tree pruning. For a free, no-obligation quotation, give us a call on 01268 642814 or get in touch here.