Garden Tips for September

By Peyton Ellas
UCCE Master Gardener

September is a busy month in the garden. The weather is cooling down and days are shorter. The September equinox, when the sun appears to cross the equator and head south, occurs between the 21st and the 24th of the month. It can still be hot, especially in our Central Valley, but during the cooler mornings and evenings, we can feel winter is once again approaching.

September is a good month to begin landscape projects and a great month to do annual or semi-annual cleanup of our climate-adapted gardens. We may even be able to begin planting, if the night time temperatures are reliably in the low sixties. But day temperatures are still warm enough for heat loving plants to bloom, and we can plant a quick crop of short-season summer vegetables. It’s also the month to finish warm-season lawn removal and solarization projects. Here are some of the things to pay attention to this month: 

Planting:  Trees, shrubs, perennials, and vines can be planted towards the middle or end of the month. Especially good to plant are California-native and Mediterranean-climate plants. If we get early rains, go ahead and start sowing wildflower seeds. Otherwise, wait until next month. Good seeds to try are California poppy, elegant Clarkia, desert blue bells, and gold fields. Herbs that can be planted are catnip, chamomile, chives, cilantro, dill, Echinacea, fennel, lavender, mint (in a container only, as it can be very invasive), parsley, rosemary, tarragon and thyme. Cool-season veggies that can be planted from seed are beets, carrots, lettuce, radishes, and sugar snap peas. Transplant seedlings of broccoli, Brussels sprouts, cabbage, cauliflower, Chinese cabbage, kale, lettuce and strawberries. It’s also time to plant garlic. Break garlic bulbs into individual cloves, leaving on the paper husks, and plant, making sure the pointed end is up. You can also plant potatoes and onions when starts are available in local feed stores and independent nurseries. 

September is also bulb-shopping time, but don’t plant yet. Store in a cool, dry, dark location until planting begins in November. When choosing bulbs, the rule is “generally the larger the bulb, the larger the flower.” Tulip and Hyacinth bulbs need to be cooled in the refrigerator for six to eight weeks before planting and must be kept away from apples to keep bulbs from sprouting prematurely.

Maintaining: Divide crowded perennials like Coreopsis, ornamental grasses, iris, and society garlic. Dig up clumps with a spading fork or shovel, discarding any old dead parts, then dividing into sections, and replanting in a bed. Harvest home-made or use purchased compost and dig lightly into the bed before replanting perennials. Water deeply, and don’t forget the two-to-four-inch layer of mulch. 

Prune and trim your climate-adapted plants like native sage, grasses, yarrow and other evergreen shrubs and perennials. Native plants that have gone mostly or fully summer dormant adapt well to a hard prune this time of year. This is the month to go through the California native garden thoroughly, removing plants that no longer work for you, adding or marking for later planting, weeding and dividing. When pruning woody shrubs and perennials like Cleveland sage, Texas ranger, germander sage, monkeyflower and lavender, cut back hard, but not completely to the ground. Remove all spent flowers and reduce the size up to fifty percent. Some plants may look like dry sticks for a month or until the fall rains come, but this will keep them long-lived and compact. You can also hard prune quail bush. Don’t prune spring-blooming shrubs like ceanothus or manzanita or you will cut off next year’s blooms. Summer and fall-bloomers like California fuchsia, California goldenrod, lantana and verbena should not be pruned yet. Wait until early spring, after frost. Wait until winter to prune deciduous trees and shrubs, when you can see and train branch structure. 

Continue to deep water trees and large shrubs until we get rain. Hose off dust and cobwebs from your plants once or twice, using a hose shut-off to avoid run off and waste. 

September is a good month to apply a preemergent herbicide to prevent annual blue grass and other winter weed seeds from germinating. Remember not to use a preemergent where you have spread seed for wildflowers or vegetables. 

Conserving: Add mulch to all garden beds, and you can also top dress with compost. Mulching can be done through the fall and winter months. Dry mulch will draw up some soil moisture, so if you can’t saturate the mulch after applying due to watering costs or restrictions, consider waiting until rainy weather. 

Pests may be a problem in the late-summer edible garden. Rather than use a pesticide, consider saying goodbye to the plants that are attracting large numbers of insect pests, composting anything that isn’t diseased and breaking the life cycle of insect pests in the garden and neighborhood. Broad-spectrum insecticides often do more long-term damage than good by killing beneficial insects. Instead use insecticidal soap, organic plant-based sprays, hand-picking, exclusion, trapping and encouraging predatory insects like spiders, praying mantis, lace wings, lady bugs and assassin bugs to help control aphid, earwigs, white fly, and other garden pests. 

If you don’t have abundant beneficial activity like butterflies, birds, moths, spiders and lizards in your ornamental garden, consider how you might change your maintenance practices and/or what plants you might add to the garden to create a haven of nature at your home. You can have a garden that is both a miniature nature preserve and is tidy, clean and organized. 

The UCCE Master Gardeners will be available to answer your gardening questions in Hanford at the KCAO Fruit and Veggie Fest on Sept. 28 and at the Greenfield Garden Workshops, 2 p.m., on Sept. 30. 

To contact the Tulare/Kings Master Gardeners, call 559-684-3325, e-mail [email protected] or write to 4437 S. Laspina St., Ste. B, Tulare, CA 93247.

– This column is not a news article but the opinion of the writer and does not reflect the views of The Foothills Sun-Gazette newspaper.

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