When Should I Prune a Holm Oak Tree?

Late winter to early spring.

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The holm oak is an evergreen tree which in some ways resembles holly, hence its alternative name, ‘holly oak’. With its dense canopy, it is beneficial for the holm oak to be regularly thinned. But when is the best time to prune a holm oak tree, and what should you look out for when doing so?

The holm oak, Quercus ilex, is an evergreen broadleaf tree of Mediterranean origin first introduced in the UK in the 16^th century. Resembling holly due to its glossy leaves that are toothed when young, it is also known as the holly oak. Holm oak is a hardy tree with a distinctive expansive rounded crown and low hanging branches. It tolerates shade well and isn’t bothered by air pollution making it a popular choice for parks, gardens and avenues.

Although it grows fairly slowly, the holm oak can reach heights of up to 20 metres and will live a good 400 years. Notable for its finely cracked, black bark and yellow spring catkins, the holm oak produces acorns that are smaller in size and more pointed than those you would find growing on an English or sessile oak tree. In Spain, the acorns of the holm oak are used as food for the pigs reared for Iberico ham.

Why prune a holm oak tree?

With its fast growing, dense canopy, the holm oak responds well to regular shaping and crown thinning. This is vital to boost air circulation and light penetration to keep the tree healthy.

It is also important to regularly prune a holm oak tree to maintain it within manageable dimensions. Whilst the stems grow very slowly, this is certainly not the case for the canopy which grows much more rapidly. Without regular pruning therefore, the holm oak will quickly start to look unbalanced. So it’s also good to prune a holm oak for aesthetic reasons.

When is the best time to prune a holm oak?

The best time to prune a holm oak is in late winter or early spring.

Diseased, decaying or damaged branches should be removed as soon as they are detected. This can be done at any time of year although care should be taken to ensure the correct safety steps are taken, and that the rest of the tree is inspected to make sure any disease has not spread.

What to look for when you prune a holm oak

The holm oak can be prone to aphids. Aphids can be greenfly, blackfly or plant lice, all of them small insects that suck sap leaving a tree listless and sometimes distorted. Some aphids will pass on plant viruses. These can lead to various issues, so if an infestation is spotted it is wise to take professional advice on chemical and non-chemical control options.

The holm oak leaf mining moth can also be a problem for the holm oak. The tree is mostly affected by the holm oak blotch leaf-miner and the holm oak linear leaf-miner. If you see brownish white blotches or uneven linear mines within the leaves then it is likely your holm oak tree is affected by one of these pests. Unfortunately there is no control for holm oak leaf-miners, however these trees do tolerate any damage caused quite well and will continue to grow even under heavy infestation. Once the new foliage starts to replace the old affected leaves, the overall appearance of the tree will start to improve.

The holm oak may also be susceptible to oak decline including acute oak decline and chronic oak dieback. Whilst these diseases are mostly connected with the English and sessile oak, there are sometimes instances of the holm oak having been affected.

Chronic oak decline – look out for:

• Deterioration of the crown over several years
• Paler and smaller leaves over time
• Dieback of twigs then smaller branches
• Dieback of larger branches

Sometimes the tree will die. But in many cases the tree will partially recover or stabilise. Recovering trees will present a healthy appearance in the lower crown but will show large dead branches in the upper crown that will project above the lower, green-coloured canopy. These take on the appearance of antlers known as the ‘staghead’ effect.

Acute oak decline – look out for:

• A dark fluid weeping from cracks in the trunk
• Multiple bleeding patches right up the height of the tree

The tree may die within four to five years but deterioration of the crown may not become apparent until just before the death of the tree.

Tree Preservation Orders

In some circumstances, trees of notable interest will be protected by a Tree Preservation Order (TPO). In such cases you should be aware that the level of pruning permissible for the protected tree will be subject to restrictions. It will be necessary to obtain permission to carry out works of any kind, so you’ll need to get in touch with the arboriculture department of your local council to check the TPO register before commencing any work. If permission is required then bear in mind that this may take up to eight weeks to be granted. What’s more, where a tree is located in a conservation area, you will need permission before going ahead with works of any kind.

The importance of expertise in holm oak pruning

The holm oak is a popular sight across our parks and gardens. It’s an attractive tree, but it does need regular attention and it is very important to know what you are looking for in terms of disease and infestation.

The best thing you can do to protect the health and beauty of your holm oak tree is call in the professionals. A qualified tree surgeon – one with the right certifications and level of knowledge – will be able to maintain your holm oak in just the right way.

When selecting a tree surgeon, never forget due diligence. Be sure to carefully check their references and certificates. Also, if you can, choose a tree surgeon with Trading Standards and local authority approval. This is a good way to guarantee yourself value and peace of mind.

If you have a holm oak tree that could do with pruning, crown thinning or professional attention, why not get in touch with the specialists at T.H. Tree Services? As fully qualified, locally respected and extensively experienced Trading Standards and local authority approved tree surgeons, we are in the best position possible to provide expert knowledge in all aspects of holm oak pruning. For a free, no-obligation quotation, call 01268 642814 or get in touch here.