What to Do in the Garden in September

During the heat waves that often occur in September, my gardening advice is to do as little as possible. Keep the garden as well-watered as you can given our current water restrictions, but other than that, don't risk heat stroke by taking on strenuous gardening tasks while the temperatures remain high. Once the heat wave passes, here's where you can focus your energy this month:

Plan

• As days get shorter, it's a good time to re-evaluate your outdoor lighting, both for safety and for ambiance. You may need to adjust timers or want to install newer, more efficient LED ligthts.
• It's time to shop for spring-blooming bulbs! Make a plan for how many you're going to add and what types, then shop the fall catalogs or local garden centers for the best price.
• Map out a system for rotating your fall crops by plant family. For example, plan on planting something from the Brassicaceae family, such as broccoli or kale, where you grew your tomatoes (Solanaceae family), or beets (Amaranthaceae) in the spot where you grew beans (Leguminosae). By rotating plant families, you can break cycles of certain pests that may overwinter or diseases that settle into the soil.
• There's still time to check with your water utility to see if you qualify for rebates for reducing your lawn.
• Make a list of the plants you want to transplant from one spot in your garden to another. Once you identify the plants to be moved you can watch for the optimal time to transplant.

Plant

• Cool-season annuals like calendula, Iceland poppies, and pansies can be seeded now. In mild winter areas, sow sweet peas.
• You can start planting spring-blooming bulbs now but focus on getting the earliest flowering ones in the ground first.
• Transition to cool-season crops, including arugula, beets, broccoli, broccoli rabe, cabbage, carrots, cauliflower, kale, leeks, lettuce, onions, radishes, spinach, Swiss chard, and turnips.
• This is a good time to plant perennials, ornamental grasses, and shrubs.

Care

• Begin fall clean-up to clear away debris but avoid heavy pruning that will stimulate new growth.
• Move potted amaryllis that you want to rebloom where they won't get any rain and withhold supplemental water as well. They will go into dormancy and foliage will die back.
• If you didn't dethatch your lawn in the spring, you can do so now.
• Cut back, divide and clean up perennials.

Water

• September is often the hottest month in California so water as much as your water district will allow, preferably in the early morning. Warm-season crops that are coming to the end can do with less water now.

Fertilize

• Feed newly planted annuals and perennials but only after they've been in the ground for at least two weeks, and only if they are well-watered and not showing signs of transplant shock.
• Fertilize your lawn only if it is green and not drought-stressed. If your lawn is brown (and it most likely is), wait until the rains come (I'm being optimistic that they will come!) and see if it greens up at all. If it does, wait until spring to fertilize. If it doesn't, wait until spring to re-seed.
• Give tropical plants, citrus trees, and roses the last feeding of the year--again, feed only if they are well-watered and not drought-stressed.

Problem-Solve

• If you see sticky webs on your plants, you may be having a spider mite infestation. If it's only on one or two plants, try blasting with the hose or wash carefully on both sides of the leaves. For a really serious infestation, you can spray with Neem oil or release natural predators like lacewings, lady beetles, or minute pirate bugs.
• Fruit drop or leaf drop on your citrus trees may be due to drought stress. Watering a drought-stressed tree too heavily all at once may cause leaves to turn yellow and fall within a few days. As much as possible given our water restrictions, water trees in the ground deeply once a week and outdoor container trees once or twice a week. Indoor container-grown citrus should get 1/4 to 1/2 gallon of water once or twice a week.

For more details on caring for your garden each month, check out my book, California Month-by-Month Gardening.

If you enjoyed this post, subscribe to my newsletter: