Hi, We have a tree lilac about 4 inches in diameter that was girdled by rodents last winter about 60% of the way around near ground level. We added a plastic protector this winter and the tree is doing amazingly well. The tree seems healthy but the damaged area has exposed dead wood in the interior of the trunk. There does not seem to be any rotting bark around the wound. Is there anything we should do to help the tree continue to survive and recover?
It’s good news that the trunk was only partially girdled – if the bark had been girdled all the way around the trunk, your lilac may not have survived.
For the degree of damage you describe, it is recommended to allow the damaged area to dry in the air. Once the lilac blooms, assess the damage – if there are dead branches, remove these. The bark will likely heal over the next several seasons. As for the dead wood in the trunk’s interior – if you’re concerned, I’d suggest contacting an arborist. You can find an arborist by searching on Landscape Ontario .
This spring and summer, make sure that you provide a healthy environment for your lilac. The tree should be getting full sun and not be crowded among other shrubs/plants – you want air to encourage good air circulation. The lilac should be watered often, and the soil should drain well — adding compost or well-aged manure on the surface of the soil can help improve soil drainage. Cut back weeds and other vegetation around the base of the lilac – to a diameter of around 1.2 metres (4 feet). Critters don’t like to be exposed and easily visible, so this might help keep them away from the tree. Keep plant debris near the lilac to a minimum, to prevent rodents from nesting. Mulch around the base of the tree, keeping the mulch back from the trunk. Finally, make sure that no uncovered garbage bags or food for pets is left outdoors – rodents attracted to these might notice the lilac!
Preventing further damage to the trunk is important. You did the right thing by protecting the damaged area over the winter. My only concern is that using plastic could prevent air exchange between the wrapped area of the trunk and the outside – this could trap moisture and create an enticing environment for bacteria or fungi to grow. This coming fall, towards the end of November, I’d suggest wrapping the trunk with tree hardware cloth, or surround it with wire mesh or a plastic tree guard (the guard should not fit tightly against the trunk – give the trunk room to breather). If using hardware cloth, it should cover the area from the base of the trunk up to at least 60 cm (2 feet) – it’s best to cover as much of the trunk as possible, as the rodents might perch on branches or other nearby structures to munch. Remove the wrap, mesh or guard around early April.
Lilacs are tough and chances are that yours will do just fine
For further reading:
Knowledgebase. It looks like my lilac… https://ask2.extension.org/kb/faq.php?id=170386
SF Gate. How to Stop Rodents From Chewing Trees https://homeguides.sfgate.com/stop-rodents-chewing-trees-66272.html
April 25, 2021