Your lawn should be dethatched and aerated every 2 years.
The first cut of the season should be mowed at 2/3 of its height. The grass actually develops thatch, which is a layer of brown leaves that grows to protect the inner leaves during the winter.
Most perennials can be divided in the spring. On a cool and cloudy day dig up your plants, cut them in half and replant them right away. I would recommend that you add some water and mycorhyze for optimal transplantation.
Your annuals should be planted later in the month, after the 20th. The temperature should be above 15 degrees on a daily basis, This will insure the survival of your annuals.
Apply mulch to keep the humidity in your flower beds and cut down on the weeding.
Plant your shrubs and trees early in the month. This will minimize the transplanting stress, use a fertilizer with a high phospherous content or mycorhize for optimal transplanting result.
Prepare your vegetable garden by adding compost and removing all the weeds. Start by planting vegetables that like a cool temperature such as lettuce and cabbage