The simple answer is a little bit of all of the above.
First, the good news. Extreme cold weather can kill off larvae and fungi. Remember our post last year about the Emerald Ash Borer? Those little guys might not be as much of a problem this summer, thanks to the polar vortex. Cold weather can lead to a better tomato growing season as well, keeping the ph in the soil low, eliminating Black Spot, and killing off aphids. Another neat trick winter can perform on your veggies? A process called cold-sweetening, where plants break down their energy resources as free sugars in order to stay warm and guard against frost damage. Just like salt spread on roads and sidewalks, these sugars protect the plant before it can freeze, with the added benefit of giving you a sweeter harvest.
The bad news? Ornamental trees are sensitive, they can get easily damaged by a harsh winter. Now is the time to prune, your Japanese Maples especially, to prevent further damage. Planting zones can be thrown out of whack be extreme weather, a zone 6 could potentially go down as low as a zone 4. You might need to replace perennials sensitive to cold like Hosta and Japanese Anemone.
No one can predict what the weather will do. Educate yourself on the best plants for your temperate zone, keep sensitive plants covered, and stay alert to falling temperatures. Your landscaper can recommend the best plants for where you live, so call a professional when in doubt. Of course, the best way to protect your landscape is early prevention in the autumn, before temperatures drop. Last year we were forced to cancel five fall clean ups because of the early snow, book early!