For the past few years, Long Island has had relatively mild winter weather. While some people enjoy warmer weather in the middle of winter, for plants the fickleness of mother nature can be extremely confusing.
During the cool season of fall, plants begin to enter dormancy. They are, for all intents and purposes, asleep. They do not put out new growth or take in many nutrients. However, when winter temperatures warm up for a long period of time (weeks instead of days) plants may break dormancy.
When trees and shrubs break dormancy they may push out flower buds or new shoots for branches. This can be a problem when a cold snap comes and cold weather returns as those buds and branches will likely die off in the cold weather. Fruit trees in particular may have their spring fruiting ability affected by extremely cold weather after warm temperatures.
Spring flowering plants may begin to push out of the ground early, breaking ground in early winter instead of spring with similar results as with trees and shrubs.
Another issue that comes from a warmer winter is that harmful insects will not be killed off. Normally, during cold winters harmful insects and their eggs are killed off in great numbers with just a few surviving through until spring. These insects hide in tree bark, the grass of your lawn, leaf piles, the shingles on your house, and more. With a mild winter, there are more resources available for pests to consume, which means that there will be a lot more pests around. Bugs like cockroaches, mosquitoes, spiders, ticks, mites, moths, bees, and wasps can all benefit from a warmer winter. Bugs that burrow into trees may also be more active in a mild winter giving them more opportunity to cause damage.
There is no good way to protect your plants from a fickle winter, but there is no need to worry as most of them will do just fine once spring comes around and the weather warms up normally. The best thing you can do is avoid heavy pruning in late summer and during the fall, as this triggers new growth that will likely be killed in the cold weather. Generally speaking, even if the cold kills off new growth and flowers the issue is only cosmetic and will resolve itself over the next growing season.