Early spring: prune, hand clear debris, add compost, begin planting, seeding.
Late spring: shear, plant, transplant, remove dead flower heads from bulbs.
Early summer: remove weeds, shear and deadhead to promote flowering.
Late summer: remove weeds, harvest, water where necessary.
Early fall: remove weeds, collect seeds, harvest, plant shrubs and trees
Late fall: plant bulbs, add compost and mulch and aerate where needed,
Early Winter: build and repair hardware, cover compost pile
Winter: stratify seeds, repair and sharpen equipment, take a break!