Late winter
Repair winter damage to limbs of small trees and shrubs
Prune evergreens and summer flowering trees and shrubs for shape
Apply dormant oil
Cut down ornamental grasses

Early spring
Cut back and feed perennial flowers
Fertilize trees and shrubs
Top dress garden with new layer of compost
Plant cool season annuals in pots/window boxes

Spring
Refresh window boxes with spring/summer flowers
Bed clean up
Divide perennials
Transplant
Mulch
Insect control

Early summer
Transplant/divide
Prune spring-flowering trees and shrubs
Insect control

Summer
Deadhead flowers
Fertilize flowers in beds and planters
Weed
Water
Insect control

Autumn
Refresh window boxes with autumn flowers
Plant new trees, shrubs, or perennials
Transplant/divide
Deadhead flowers
Plant spring-flowering bulbs

Late Autumn/Early winter
Prepare beds for winter
Protect shrubs/young trees from weather (wrap or spray anti-transpirant)
Install deer fencing and apply deer repellant
Refresh window boxes with holiday greens
Hang garlands, wreaths, lights