I have a new lawn,trees,bushes and flowers when do i fertilize them?

Fall is the best time to fertilize, especially for new plantings.
You need to have your soil tested to be certain of the appropriate type of fertilizer need. Cool-growing grasses need less nitrogen (the 1st # in fertilizer, 5-10-10) Grasses that grow best in the warmth of summer need more Nitrogen.
Also, keep the soil aerated and well watered through the winter. Trees and shrubs may look dormant on the outside, but deep inside they are still preparing to be reborn! Don't forget that spring feeding though!