September is for planting! The soil is still warm but the air is cooler and moisture is (usually) more abundant. These conditions are great for establishing most herbaceous perennials, trees and shrubs. Planting them now will give you a head start on spring. The exception to this is broad-leaf evergreens like rhododendrons, boxwood and hollies as well as plants that are borderline cold hardy (for us, zone 7 or higher). These are better planted in spring.
Give your ornamental planters a boost. Remove or trim back any ragged annuals. You can replace them with hardier fall plants.
Now is a good time to save some seeds for planting next year. Seeds from many annuals like Zinnia, Marigold, Cosmos, and Celosia are easy to save in a cool dry place. Just be aware that some hybrid varieties will not be identical when grown from seed.
Speaking of seeds – get after those weeds! Many weeds like Japanese stilt grass, yellow oxalis, pokeweed and various grasses are setting seeds. Getting rid of them now will help reduce populations next year. Also remove the flower heads of self-seeding annuals and perennials if you don’t want the seedlings.
There is still time to add cold hardy vegetable starts (lettuce, kale, broccoli, etc.) to the vegetable garden. If you are quick you can still seed in lettuce, radishes, kale and spinach.
While Peonies can live a very long time without dividing, now is the best time to divide them if you want to increase your plants.
Now is a good time to do soil tests. If pH needs to be adjusted, this is best done in fall to prepare for spring planting.
It’s also a good time to start a new planting bed by laying down cardboard and then layering woodchips, twigs, stems and fall leaves when they fall. By spring, the area should be ready for planting.
Think about bringing in any houseplants vacationing outside. They should come in before nights hit 50F. Inspect for pests (especially mice living in large pots – ask me how I know…).
You can also bring in some herbs and place them in a cool, sunny spot in pots with good drainage.
Make a list of potential new plants to add to your landscape and have the list handy when fall plant shopping. If you don’t have a specific plant in mind, make a list of the spaces you want to fill – including the amount of space, the light and moisture conditions and any height constraints. You can use this to help choose plants when shopping.
Keep swatting those lanternflies…