September Gardening To-Do List

Monthly Chores for Each Region

Wheelbarrow and gardening supplies.

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September is unpredictable in the North. Some years, the weather approximates perfection. Other years, the heat of August drags on through September; then again, it can bring rain.

That unpredictability is even worse in the Southeast. If you are not plagued with heat, then you are plagued with hurricanes. Find out what you should be doing in the garden in September, wherever you live.

All Regions

  • Turn your compost pile over one last time.
  • After the long summer, your flower beds are in need of some tidying up. Cut back perennials that are done blooming. Trim off diseased vegetation and dispose of it properly (do not compost it).
  • Take cuttings from plants that you want more of.
  • Spray Japanese knotweed while it is blooming. The herbicide will have the most impact now.

Mid-Atlantic

Hot weather will likely continue in September in the Mid-Atlantic. But there will be good days, too, and you should take full advantage of them. Your garden will appreciate the attention.

  • Stop pruning and fertilizing, as you do not want to encourage tender growth at this time of year. But do continue watering annuals, perennials, and vegetables that are still growing.
  • Start bringing in houseplants that you have been keeping outdoors during the summer. Inspect them first for pests so you do not bring the pests inside.

Midwest

Although the Midwest still sees some hot weather in September, the trend is clearly to more moderate temperatures, which means good times in the garden.

  • Plant a cover crop: It will help you avert erosion during the winter.
  • In far northern regions such as northern Michigan and Minnesota, plant spring bulbs.
  • (Late September:) Buy or make a scarecrow and set it up on your lawn to decorate for the harvest season and to get the jump on Halloween decorating.
  • Plant those bargain-basement annuals that you nursed back to health in August as soon as temperatures cool off. They will only last until the first frost, but they provide great color for the fall garden.
  • Stop watering both evergreen and deciduous trees in late September. This will help them prepare for winter. Resume watering later in the fall, after the deciduous trees have dropped their leaves.
  • Divide perennials as needed.
  • Dig and store tender bulbs such as dahlias, cannas, and elephant ears.

Northeast

September in the Northeast can be the best of times, although the weather varies greatly from year to year. Regardless, you will want to spend as much time in the garden as possible, because wintry weather is not that far away.

  • Plant a cover crop: It will help you avert erosion during the winter.
  • In far northern regions such as northern Maine, plant spring bulbs.
  • Stop watering both evergreen and deciduous trees in late September. This will help them prepare for winter. Resume watering later in the fall, after the deciduous trees have dropped their leaves.
  • Divide perennials as needed.
  • Dig and store tender bulbs such as dahlias, cannas, and elephant ears.
  • (Late September:) Buy or make a scarecrow and set it up on your lawn to decorate for the harvest season and to get the jump on Halloween decorating.
  • Plant those bargain-basement annuals that you nursed back to health in August as soon as temperatures cool off. They will only last until the first frost, but they provide great color for the fall garden.
  • Harvest the tender components of your garden when the first frost is predicted (which can be either this month or next). This is obvious for a soft fruit, such as the tomato.
  • But it is a good idea to harvest even ornamental gourds and pumpkins before a frost because they can suffer some discoloration after a frost.
  • A light frost will not hurt winter squash fruits, but it will kill the leaves; once the leaves die, it is time to harvest anyways, because growth will stop.

Pacific Northwest

As usual, the Pacific Northwest offers moderate temperatures in September. In Seattle, for example, the average high is 71 degrees F and the average low 53 degrees F; expect 8 days of rain.

  • Plant shrubs and trees.
  • Order spring bulbs.
  • Weed your beds to prepare them for winter.

Pacific Coast

September weather in Northern California is moderate. The average high in San Francisco, for example, is 70 degrees F, the average low 55; you will get hardly any rain. Southern California is predictably warmer, with an average high of 83 degrees F and an average low of 63 degrees F in Los Angeles, for example, with virtually no rainfall.

In Northern California:

  • Stay ahead of harvesting your summer vegetables.
  • Start your fall/winter garden. Direct sow the seeds for beets, carrots, and radishes.
  • Water fruit trees deeply, and clean up any fallen fruit as part of your pest/disease control efforts.

In Southern California:

Southwest

In the high desert, temperatures start to moderate in September. In Santa Fe, New Mexico, for example, expect an average high of 78 degrees F and an average low of 47 degrees F; you will get about 6 days of rain. In Phoenix, Arizona, you will have an average high of 100 degrees F, an average low of 75 degrees F, and hardly any rain.

  • Keep fruits picked as they ripen.
  • Plant new cacti.
  • Practice whitefly control on plants such as lantana. If you spot any whitefly on the undersides of the leaves, immediately spray with Neem oil.

Southeast

The weather can start to become a bit more moderate in September in parts of the Southeast. Atlanta will see an average high of 82 degrees F and an average low of 65; this city will get 8 rainy days in September.

  • It is time for the fall vegetable garden. Start seeds of heat lovers such as tomatoes and peppers.
  • Direct sow the seeds for lettuce, greens, onions, peas, beans, and broccoli.
  • Sow the seeds for cool-season annuals.
  • Keep fruits picked as they ripen.