General and conventional wisdom says that snow and ice can make tree branches brittle which is bad for the branches. Well for that reason – you don’t shake the branches. If they’re already compromised as-is, you’re not helping things by aggressively manipulating them and moving them around.
So while, on the whole – we recommend leaving them alone – there are a few things you can do to take the edge off your tree’s pain. For one – it’s okay to brush off the dry fluffy ‘top snow’ with a broom. That being said, be sure to do this immediately before or after a storm. You don’t want to let the moisture and ice kick in. And while you’re sweeping, be sure to sweep upward rather from the top down. Don’t do anything to push the branches down further.
If – at any point – the snow or moisture freezes – then DO NOT brush it off. That’s the best possible way to actually break the branches themselves and cause significant damage. Wait for the snow and the ice to melt completely before inspecting for any breaks or damage. You’ll likely end up doing this in the spring – when the weather has warmed up significantly. It’s at that time that you’ll want to inventory any and all damage, remove detritus and in the event that you do have a catastrophic injury pertaining to your tree – it’s time to simply call in a professional.
So once the cold stuff hits, be sure to leave your trees alone! Meddling more – while you’ll certainly be tempted to do so – isn’t good for your tree and could cause even more damage than you assumed would happen otherwise. When in doubt, contact a certified arborist. They have experience and a few techniques to help alleviate your trees’ stress.