September Garden Checklist for the Northeast

September is my favorite month—gardens have matured into lush abundance, spilling onto sidewalks and over fences with eye-popping annuals, textural grasses, and herbs. Weekly farmers' market visits are a delight with so much to see and buy. But there's plenty to do to keep things looking their best. My garden carts become indispensable as I cut back perennials, add to the compost pile, and haul loads to the back corner.

Welcome Wildlife with Flowers

Many annuals peak now, like multi-bloomed sunflowers on strong stems. Beyond being great cut flowers, sunflowers feed pollinators; leave seed heads standing to attract finches and other birds.

Late-blooming perennials like aster and obedient plant (Physostegia spp.) take center stage, luring migrating monarchs headed to Mexico. New England aster 'Alma Poetschke' (Symphyotrichum novae-angliae 'Alma Poetschke', zones 4–8) is a standout.

Another extended bloomer is mountain fleece flower (Persicaria amplexicaulis 'Firetail', zones 4–7), a native perennial with terminal spikes in pink and raspberry. Excellent for wet soils, woodland edges, or naturalistic borders with colorful zinnias.

Summer isn't summer without zinnias. Started in the greenhouse in April, by mid-September they're huge and need support from canes or twine along the vegetable garden border. Today a tiger swallowtail hovered on a large white zinnia.

Add Late-Season Texture

Grasses are in full glory at garden centers this month—perfect for adding to your garden. Massed, they become living sculpture. Tall varieties shine against hedges, walls, or fences.

Grass colors shift daily—seed heads brown, foliage yellows into caramel and rust. Here fountain grass pairs beautifully with willow blue star (Amsonia hubrichtii, zones 4–9) in my Vermont garden.

Other fall texture favorites: switch grass (Panicum virgatum 'Heavy Metal', zones 5–9), little bluestem (Schizachyrium scoparium 'Blaze', zones 3–9), and feather reed grass (Calamagrostis acutiflora 'Karl Foerster', zones 5–9).

Reap the Harvest

The green smoothie craze is big here. With a high-powered blender and homegrown kale, parsley, celery, lettuce, arugula, and beets, you can make power meals. Even without a blender, all are nutritious—get busy in the kitchen. Sow cool-season crop seeds now for a late harvest.

Tomatoes are plentiful and hard to resist. I savor fruits ripening on the vine. Here in the Northeast with our short season, indeterminate tomatoes produce for an extended period—the highlight of summer for many.

Feed the Birds with Fruiting Shrubs

Bird activity increases in my mixed border where viburnum and redtwig dogwood provide street-side privacy. Viburnum 'Mohican' is especially showy, with fruits shifting from red to black and leaves turning red as days shorten.

Another great wildlife shrub is aronia (Aronia arbutifolia 'Brilliantissima', zones 4–9), commonly called chokeberry. Unbeatable fall color, fruits persist well into autumn.

Other September Chores

• Cut back perennials
• Trim hostas and daylily scapes
• Plant mesclun, lettuce, arugula, kale, and other cool-season crops

More U.S. garden guides