Seasonal Care of the Garden
Shrubs
Prune hedges in late September or early October, so they will look neat & tidy through winter.
Plant evergreen shrubs & trees once night temperatures turn consistently cool.
Prune any dead branches on trees & shrubs before leaf drop.
Stop fertilizing roses approximately 45 days before anticipated first frost.
Perennials
Prepare flower beds for fall planting, improving soil with compost or leaf mold.
Transplant seedling perennials from seed flat to nursery bed.
Plant new spring-blooming perennials such as Siberian bugloss, Brunnera macrophylla, and dwarf bleeding heart, Dicentra eximia.
Perennials such as daylilies, phlox, Siberian iris, & hosta can be divided now.
Thoroughly water newly planted perennials, and continue to do so if rainfall is sparse.
Peonies can be planted from late September into October. Exceptionally long lived, peonies need thorough site preparation.
Bulbs
Hardy bulbs for spring bloom should have been ordered earlier, in summer.
If purchasing locally, choose plump, solid, heavy bulbs, avoiding any moldy or shriveled ones.
Begin planting when the soil cools off later in the month. Note - fall-flowering bulbs such as Colchicum are planted as soon as available.
Begin by planting smaller bulbs such as crocus & snowdrops, & any bulbs that don't have a papery covering (tunic).
Next plant daffodils & hyacinths. Tulips can wait, and may be planted from late October into November.
Annuals
Take cuttings of tender perennials such as coleus, impatiens, & pelargoniums to winter over on window sill.
Plant ornamental cabbage & ornamental kale as cool season annuals.
Keep an old sheet handy to cover your most tender flowers such as dahlias.
If protected from the first frost they'll often bloom for a couple of weeks longer.
Vegetables
Plant cool season crops such as lettuce, spinach, other greens transplants.
Radishes may still be seeded early in Septemberfor a late crop.
Pinch tops of Brussels sprouts to fatten developing sprouts.
Keep picking broccoli to encourage production of side shoots.
Pick any little tomatoes unlikely to ripen. Consider pickling green tomatoes.
Sow winter rye as crops are harvested.
Pot up tender rosemary (hardy only to about 28° Fahrenheit) to bring in for winter.
Lawn
Begin fall seeding or sodding.
Core aerating may be done at this time.
Fertilize but do not use weed & feed formulation if re-seeding.
Apply broad-leaved weed control.
Miscellaneous Tasks
Add organic matter such as aged manure or compost to garden, increasing humus level in soil.
September is a good time to have your garden's soil tested for nutrient levels & pH.
Remember to bring tender houseplants indoors in early to mid-September.
Christmas cactus & tender azaleas can remain outdoors until night temperatures fall below 40° Fahrenheit.
Begin gathering pods & grasses for dried arrangements.