Your Fall Garden Starts Now: What to Plant, Prune, and Prep in September

Depending on your location, September is pumpkin spice latte weather or still hot enough for shorts and a dip in the pool. More often, we get some of both in this transition month. And as summer’s slower pace of life starts to speed up again, it’s easy to miss important gardening tasks that help set you up for success next year. Keep your garden going strong through the rest of the season with these checklists of garden activities, depending on your region.

Northern Region

In the northern states, such as Minnesota, Maine, or Michigan. September means cool nights, pleasant days, and the beginning of the end for many of our favorite summer plants. Snapdragons are weary, the tomato plants look a bit messy, and the pumpkin vines have fully taken over instead of staying in their corner of the garden.

For many gardeners in the northern tier, this month brings the first frost scares, if not the first actual killing frosts. To be prepared, have your frost cloth ready, along with the twine and posts you’ll need to hold it up.

Vegetable and Herb Garden

Keep up with the harvest, and start watching the weather forecast. It does not take an actual frost to damage tender crops. For example, basil turns black when nighttime temperatures drop into the 40s. Any threat of frost means it’s time to salvage whatever harvest you can from tender crops like tomatoes, beans, summer squashes, eggplants, and peppers.

• Depending on your location, September may bring dry spells or excessive rain. Check the soil moisture and don’t forget to water if needed, so those crops can finish strong.
• Keep sowing succession crops of lettuce, kale, and other leafy greens, as well as radishes and beets. Seeds are often on sale in the fall, and you might have a longer growing window than you think. 
• Plant a cover crop in the empty beds. It will sprout quickly; let it grow until it dies back, and dig it under in the spring.

Flower Beds, Perennials, and Ornamentals

Now is the time to gather armfuls of the last flowers of the season for fresh bouquets, as well as for drying flowers. 

• Plant fall bulbs like daffodils, snowdrops, and tulips.
• Prepare a spot and plant peony roots, so they get a start before the ground freezes.
• Plant perennials, trees, and shrubs up until 6 weeks before the first expected hard frost date in your area.
• Keep windfall fruit cleaned up under trees. Fruit left on the ground creates a mess and harbors pests and pathogens over winter.

To-Do Checklist

• Prep your garlic bed, but don’t plant it just yet.
• Water and turn your compost pile one last time.
• Remove any diseased plant material and dispose of it in the trash; don’t let it sit on the soil, and don’t compost it.

Middle States

Gardeners in Kansas, Virginia, Missouri, and other states in the middle latitudes finally get a bit of a break from the heat. This makes your plants perk up. Evenings are pleasant and nights are cooler, but daytime temperatures remain hot. Despite the fall equinox and the first official day of fall approaching, your garden still needs water and care.

Vegetable and Herb Garden

Harvest time continues, and if your pumpkins are ready too early, store them off the ground and out of the sunlight. Remember to buy your mums at the garden center for fall displays, but don’t forget to water them daily if needed. 

• Plant cover crops in garden beds as they empty, like after you’ve dug any late-season potatoes, or ripped out the sweet corn stalks.
• Keep succession planting beets, lettuce, peas, radishes, and spinach. Shorter days and less powerful sun mean these can go right out in the open with no need for shade.
• Transplant broccoli, kale, and cauliflower into fall garden beds.
• Harvest summer herbs for drying, and take cuttings of others to keep them going indoors over the winter months.

Flower Beds, Perennials, and Ornamentals

As summer draws to a close, cut down on fertilizing your perennials, as they prepare for dormancy—that’s one thing less to remember. September is a good time to take inventory and lay the foundation for a beautiful yard next year.

• Save seeds from flowers you want to keep, and carefully label them before storing the seeds in a cool and dark place. Clear identification of seeds is important, as you won’t remember what they are next spring. 
• Plant peony roots and fall perennials, shrubs, and trees starting later this month.
• Keep up with weeding and mulching.

To-Do Checklist

• Begin quarantining plants that you’ll bring indoors for the winter to avoid introducing pests to your houseplants.
• If you have received soil test results, now is the time to add amendments to replenish nutrients or adjust the pH. 
• Fall conifer needlecast begins, and you don’t want to miss out on all that pine straw.
• Build a cold frame for extended fall gardening starting next month.

Southern Region

Heavy rains, or none at all, are normal in this month of change. Water deeply during dry periods, especially new perennials, shrubs, and trees you planted this year.

Vegetable and Herb Garden

In Southern gardens, September starts an entirely new gardening season. With frosts still two or more months away, it’s time to get outside and get those fall crops planted. 

• Continue succession planting fall crops of collards, kale, turnips, and cold-loving cabbages. 
• Pinch off the growing tips of vining crops, such as indeterminate tomatoes, squash, and melons, to force the plants to redirect their energy to fruit production. 
• Plant out transplants of broccoli, cabbage, Brussels sprouts, and cauliflower later in the month if the weather cools.
• Give tired herbs a good trim, forcing a flush of new growth for harvest next month.

Flower Beds, Perennials, and Ornamentals

Perennials and annual flowers tend to look a little bedraggled at the end of the summer. Thankfully, September brings some milder temperatures and more rainfall, which is a good time to refresh your beds and containers by planting mums, pentas, pansies, and other cool-season flowers.

• Don’t deadhead any flowers you plan to save seeds from so they can set seed heads. Keep deadheading all other flowers.
• Get new beds ready for next year using the lasagna gardening method.
• Cut down on fertilizer to allow new growth to harden off.

To-Do Checklist

• Order garlic for fall planting.
• Purchase or order perennials, shrubs, and fruit trees to plant later this month and into October.
• Mark out which perennials you’d like to divide next month and where you might put them. 
• Water and turn your compost pile.