September

Stop trimming, dead-heading and fertilizing.  

Plants are beginning to slow down in advance of winter, and trimming, dead-heading and fertilizing encourage growth. New growth is most harmed by frost, which may cause the plant long-term damage. Let your plants begin to go to sleep. 

Divide and move perennials.  

Perennials can be divided at many points during the year, but fall is best. It allows perennials to build root systems over winter, then pop up in spring, raring to go.  

Pick herbs to dry or freeze. 

Some herbs may overwinter where you are (I can pick thyme, rosemary, and oregano any time of year), but tender herbs like basil, tulsi, chives, mint, calendula and dill need to be picked and saved now. Parsley and cilantro will keep growing in the cool weather, but will die back at your first freeze — though you may be able to grow them under protection all winter. Lavender may be sending out a last burst of blossoms, and those should be picked now, too. I dry bundles of lavender and sage.  

Plant trees and shrubs. 

This is the optimal time of year to plant bare-root trees and shrubs, which use the winter to send out roots and are ready to grow in spring. 

Plant early spring flower bulbs. 

Plant daffodils, hyacinth, crocus, and early irises in-ground or in pots. If you have indoor bulbs like amaryllis, plant the bulb now for a bloom time around Christmas. If you’re planting tulips, wait until the weather is colder: October at least, but November is better. This is to prevent the tulips being infected by a fungus that’s more prevalent in warm weather. 

Take photos of your garden. 

Take photos of the garden now, while almost everything is still green and growing, to help with winter planning. You think you’ll remember precise locations and sizes of your plants, but you won’t. Take photos. 

Plant winter flowers. 

Your local nursery probably has mums, pansies and other winter flowers for sale now. Plant them in the garden or in pots for a little autumn and winter cheer. 

Remove pumpkin & winter squash blossoms. 

At this point in the year, your pumpkin and winter squash is probably still blooming — but there’s no chance that those blooms can form edible squash before your first frost date. Pinch off winter squash blooms from the beginning of the month, to force the plant to put its energy into ripening the squash already on the vine. 

Plant any remaining fall crops & biennial or perennial flowers or herbs. 

Plant any fast-growing, cool weather crops that aren’t already in the garden or in a seed tray — like lettuce, mustard, chard, radish, and arugula. Plant any additional perennial or biennial herbs or flowers. They’ll be slow to grow over the cooler months, but be patient. 

Harvest and preserve. 

The final summer crops are coming in now, especially flint or dried corn, the last of the summer squash, eggplant, basil, and whatever hasn’t yet succumbed to pest or pestilence. Leave the corn stalks standing in the garden to dry in place, then cut and gather them around the end of the month for fall decorating. 

Cut back any dying pond plants. 

Aquatic and marginal plants may be dying back, dropping their dead and dying foliage into the water. Trim it off and pull it out of the water to prevent a release of nitrogen into the water, which encourages algae growth. Leave the plants by the water’s edge for a day or two, please, to allow small creatures time to crawl back into the water. 

Sow grass seed.  

The best times to sow grass seed are in early autumn and early spring.