September

September Gardening Tips for Los Angeles County Residents
by Yvonne Savio

-- This month's discussion of garden tasks is based on my 60 years of gardening at my home in Pasadena.
-- For my comments on current weather conditions and activities, see my blog page which includes archived blogs since 2015.
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September's mildness makes just about any gardening tasks pleasant. The soil and air are warm but not overly hot. Fresh summer produce is still delicious, but production is slowing down. Garden tasks center around cleaning up the old garden and getting the new one started. Seeds and transplants of cool-weather-hardy crops can be planted now for harvests from fall through early spring. Seeds sown now for spring blooms and crops--especially edible peas and flowering sweet peas--will encourage strong root and foliar development that will survive most frosts, thrive, and bear sooner in the spring. Soil amendments can be collected and dug in now to break down over the winter, enriching the soil for next year's gardens.

Vegetables and Fruits

Sow beets, bok choy, broccoli, Brussels sprouts, cabbage, carrots, cauliflower, celery, chard, chervil, chives, collards, endive, garlic, kale, kohlrabi, leeks, lettuce (in our hot climate, this is the best time for sowing and transplanting heading types), green onions, short-day bulb onions (like Grano, Granex, and Walla Walla), parsley (the flat-leaf type is more winter-hardy than the curly one), parsnips, peas, white potatoes, radishes, spinach, and turnips.

Sow or transplant two or three times the amount you would for spring harvest, as these overwintering crops will grow very slowly, and you'll harvest only a couple of leaves a week from each lettuce plant.

As some herbs reseed themselves, transplant them for overwintering either into the garden or indoors. Dill, especially, seems to germinate better when you sow it at the same time that its self-sown seeds germinates in the garden, so take advantage of it.

Consider sowing some frost-tender herbs for fresh use indoors all winter long. Seeds can be started either indoors or outdoors now, but they must be moved indoors by next month. This will allow them to acclimate to the warmer and drier indoor conditions before it's too cold outdoors.

Quite a few herbs make attractive edible houseplants, including both dark green and dark opal basil, chervil, chives, dill, mint, oregano, parsley (the flat-leaf type is hardier and more flavorful than the curly kind), rosemary, summer savory, sweet marjoram, and thyme. Sow the seeds thickly to guarantee good germination, as plants will grow slowly over the winter, and consequently less foliage will be available each time you'll harvest.

Problems with seed germination may be due to old seed, soil that is too warm or has been allowed to dry out, or seeds that were sown either too deeply or not deeply enough.

Keep seedbeds moist and shaded from hot afternoon sun until the seedlings develop two to four true leaves. After transplanting them, mulch the soil lightly to hold moisture for better germination, and add more in October and November for additional frost protection. Keep the mulch an inch away from the plant stems, however, for good air circulation and less potential for disease problems.

Vegetables that tolerate light frosts and temperatures in the upper twenties will extend the growing season and provide fresh produce all winter long. These include beets, Chinese and savoy-leafed cabbages, collards, kale, butterhead and heading and romaine lettuces, flat-leaf parsley, radishes, turnips, savoy-leafed spinaches, and Swiss chard. Plants that have developed deep root systems and mature leaves are more tolerant to the cold. When these plants are three or four inches in size before the first hard frost, they're mature enough to be harvested throughout the fall, winter, and early spring. However, these will bolt at the first real warmth of early spring so they can't be counted on to provide a crop after that. But, by then, you'll have made the first spring plantings, so the gap between harvests won't be too long.

When sowing cover crops for the fall and winter, consider edible ones. Kale and rocket (roquette, arugula) are full-flavored leafy vegetables that withstand freezing. Both germinate in cool weather and are welcome fresh greens for stir-fry and soups all winter long. In the spring, they can be easily turned under as "green manure" when preparing the soil for the main spring and summer crops.

Pinch out new blossoms and growing tips of melons, winter squashes, and determinate tomatoes to force growth into the fruits that have already set. Any that set from now on won't ripen sufficiently before cool weather comes--unless you want lots of immature green tomatoes around Thanksgiving. Indeterminate cherry tomatoes, on the other hand, can be allowed to continue setting, as the little fruits ripen more quickly.

Plant new trees while the soil is still warm to encourage the roots to get established before going dormant for the winter. Trim off dead wood and suckers and watersprouts (quickly-growing upright shoots), but leave major pruning for January, when the trees are dormant.

Feed citrus for the last time this year, and water trees less as the weather cools and the rains (hopefully) take over. Cupped, wilted, or falling leaves signal moisture stress from hot winds, which can occur even when the soil is damp. Provide lath, shade cloth, or other semi-open material for protection. Pale green new citrus leaves may need a dose of liquid chelated iron or a solution of fish emulsion and kelp.

Remove and destroy fruit mummies on the ground or still on the tree to reduce the chance of brown rot next year.

Strawberries with whitish or yellowish leaves need to be fertilized one last time with a high-nitrogen food. After that, fertilizer them with a low-nitrogen, high-phosphorus, and high-potassium fertilizer to help them harden off for the winter.

Sun-dry the last prune plums, grapes, figs, apples, and pears. Be sure to keep the moist pieces separate so the surfaces can form a seal against spoilage.

General

Continue replenishing your compost pile. Spent annuals and vegetables add a lot of bulk now, along with grass and other garden clippings, and non-greasy trimmings from the kitchen. But, leave out plants that are obviously infected with diseases--destroy or dispose of these, instead. Chop up bulky items to help them decompose faster. Layer greenery with a bit of soil and dry matter. Keep the pile moist but not waterlogged, and turn it or loosen it up every other week or so to let in air.

Dig in organic soil amendments to break down over the winter, enriching the soil for next year’s garden.

As you clean up dried foliage from bulbs, mark their locations, so you don't damage them when digging later in the season.

Hose off plant foliage--both top and underneath leaf surfaces--to lessen insect populations. This is especially helpful to get rid of aphids, caterpillars, mealybugs, spider mites, and whiteflies on beans, collards, kale, tomatoes, and roses. Be sure to do this early enough in the day (preferably early morning) so that the foliage can dry completely by sunset.

An old paring or putty knife can be used to cut transplants out of a flat or to aid harvesting.

Old tires can serve a variety of uses besides as tree swings. Single ones filled with soil form small-scale raised beds. Use a porous mixture of potting mix for extra good drainage. Several tires stacked on top of one another form deep barrels for potatoes and tomatoes. Overlap tires up a slope, filling each with soil and planting ground cover for excellent reinforcement of unstable embankments or where there's little soil. The tires retain heat, resulting in extra late-fall and early-spring growth.

Use a garden hose to help plan a curved landscape area. Its position can be changed easily until the desired shape is determined.

Cut off the bottoms of plastic gallon jugs, use the tops as mini-greenhouses, and use the bottoms as saucers for pots or shallow starting trays. Cut a slit from one side to the center, and cut an inch-wide hole at the center for a perfect cutworm guard for tomato plants next spring.

Tops of garbage cans, especially plastic ones with no handles, make easy-to-scoot-around receptacles for weeds or harvested fruits and vegetables. Unlike larger and heavier bucket-shaped containers, these won’t mar delicate plants as you work along ground covers. Their broad, shallow surface makes them perfect for harvesting delicate vegetables and fruits that are best kept in a single layer.

Ornamentals

Sow or transplant ageratums, alyssums, asters, astilbes, baby blue eyes, baby's breath (gypsophila), bachelor's buttons (cornflower), begonias, calendulas (winter or pot marigold), campanulas (bellflower, canterbury bells), candytufts (iberis), carnations (dianthus, pinks, sweet Williams), chrysanthemums, clarkias (godetia), columbines (aquilegia), coralbells (heuchera), coreopsis (pot of gold, calliopsis), gloriosa daisy (rudbeckia, black-eyed-Susan, coneflower), Shasta daisy, English daisy (bellis), delphiniums, forget-me-nots (myosotis), foxgloves, gaillardias (blanket flower), gerberas (Transvaal daisy), geums, hollyhocks, impatiens, larkspur, linarias, lobelias, lunarias (honesty, silver dollar plant, money plant), nemesias, nigellas (love-in-a-mist, Persian jewel), pansies, penstemons (bearded tongue), phloxes, Iceland and Oriental and California poppies, primroses (primula), salvias, snapdragons, statice (limonium, sea lavender), stocks, sweet peas, verbena, and violas.

Several companies offer individual varieties and collections of California wildflowers that are grouped by color or geographic area or other characteristics such as drought resistance.

For very fragrant sweet peas, rely on some old-fashioned varieties such as Antique Fantasy and Painted Lady, or new cultivars that have the distinctive fragrance bred back in, like Leamington, Rosy Frills, Royal Wedding, and Snoopea.

Plant cyclamen and primroses where they're shaded from the still-intense afternoon sun for color through next spring.

Other fall-color perennials include fortnight lily and Kaffir lily.

Bring in houseplants from their summer breather outdoors after grooming them and thoroughly checking them for pests. This is a good time to repot them in fresh potting mix. Toss the "old" mix out into the garden or onto the compost pile. Keep newly repotted plants in a bright area indoors for three weeks to let them gradually get used to the darker, warmer, and drier indoor conditions. Then move them to their winter homes indoors--but away from drafts and heaters.

Transplant perennials, ground covers, shrubs, and vines while the soil and air temperatures are still warm to give them a full season's root development over those planted in the spring. Set them out in the cooler late afternoons or evenings, and water them in with a mild solution of a balanced fertilizer to promote new root growth and reduce transplant shock. Mulch and shade them lightly for the first week. Add more mulch in October and November for additional frost protection.

Transplant shrubs and trees no later than six weeks before the soil temperature drops to 40 degrees or lower to give them enough time to settle in. This is especially helpful for flowering crabapples, forsythias, English ivies, junipers, honey locusts, maples, pines, rhododendrons, spruces, and yews.

Switch to a 0-10-10 fertilizer for azaleas, camellias, gardenias, and rhododendrons to encourage formation of next spring's blossom buds. Increase the spring bloom size of azaleas, camellias, dahlias, and rhododendrons by removing half of the new flower buds. For extra-large camellia blooms, remove all but one bud per branch; leave some further down on the bush for later bloom.

Prolong blooming on tuberous begonias, dahlias, and fuchsias by pinching off faded flowers. Water them frequently while the weather is still hot, and then feed them with a low-nitrogen, high-phosphorus fertilizer before they begin to go dormant.

Divide and replant crowded perennials such as agapanthus, coralbells, Shasta daisies, daylilies, phloxes, and yarrow. Stake tall-growing mums before they get too top-heavy and fall over, unless you prefer a cascading or curly-stemmed display. Feed mums until the buds show color and begin to open.

Cut back alyssum, coreopsis, marguerite and Shasta daisies, delphiniums, dianthus, felicias, gaillardias, geraniums, ivies, lantanas, lobelias, petunias, and santolinas to one-third or one-half of their present size. However, don't cut them back beyond the green foliage to the older woody growth, as this may kill the plant.

Root the cuttings of semi-woody plants, including fuchsias, geraniums, hydrangeas, ivies, and marguerite daisies. Remove all but the top four leaves, and bury at least two nodes (but preferably four or five) on the stem in damp potting mix. They should be ready to transplant in two months.

Plant iris rhizomes, daylily crowns, and lily bulbs in well-drained soil amended with organic matter. Irises prefer to sit on top of the soil, with only their roots buried. Daylilies like to be one inch below the soil surface. Lilies need a three-inch layer of humus on top of their roots. Irises can take all the sun they can get, daylilies will bloom nicely in full sun or partial shade, and lilies need their bases shaded but foliage in the sun. Plant lily bulbs as soon as you get them, and keep soil or potting mix always slightly moist as the bulbs don't ever go fully dormant even after losing all their top foliage.

Trim bearded iris foliage fans to about eight inches from the rhizome. Plant new irises and divide others if they have less than an inch of soil space between them or if they didn't bloom well last spring. Discard the old, leafless center sections, trim the roots of the newer ones to two inches in length, and plant them just below the soil surface. Don't fertilize them, but water them in well after planting and every other week until the rains take over.

This is the last month to prune roses and feed them for their last bloom cycle before going dormant. Hold off on severe pruning until plants are fully dormant in January. Feed plants lightly, and water. Continue to water them only in the mornings to lessen mildew and other wet-foliage-at-sunset-with-warm-evenings disease problems.

Bulbs to plant for spring bloom can be purchased now for first-choice quality. These include alliums, amaryllis, anemones, brodiaeas, crocuses, daffodils, freesias (so fragrant!), fritillarias, galanthus, baby glads, glory-of-the-snows, grape and Dutch and wood hyacinths, Dutch irises, ixias, leucojums, lycoris, montbretias, narcissus, paperwhites, peonies, ranunculus, scilla, snowdrops, sparaxis, tigridia, tritonia, triteleia, tulips, dog-tooth violets, watsonias, and winter aconites. Choose big, plump bulbs, as these have the most stored food and will produce the largest and most numerous blooms over the longest period of time. They cost a bit more, but they'll provide a great deal more pleasure when they bloom. Refrigerate hyacinths and tulips for six to eight weeks before planting them in November.

Especially fragrant freesia cultivars include Athene, Allure, Demeter, Excelsior, Golden Wave, Mirabel, Pink Westlind, Snowdon, and Welkin.

If you like having blooms in the lawn, choose bulbs that are good for naturalizing, since the ripening foliage following bloom won't interfere with mowing the lawn, including Chionodoxa, eranthis, muscari, ornithogalum, and puschkinia.

Don't forget to buy some bulbs just for indoor forcing color from Thanksgiving through January. Good choices include amaryllis, crocus, freesias, lily-of-the-valley, paperwhites, and tulips.

Store the bulbs in a cool, well-ventilated area until you're ready to plant them. Chill crocus, daffodil, hyacinth, narcissus, and tulip bulbs in a paper bag on the lowest shelf in the refrigerator--at about 40 degrees--for at least six weeks. Wrap them in paper--not plastic--bag, since the bulbs are alive and must breathe.

Enrich the soil where the bulbs are to be planted with compost, bone meal, and granite dust or wood ashes (but not from charcoal briquets used in the barbecue, which contain harmful chemicals). Also, add some nitrogen, as it is easily washed from the soil by irrigation and winter rains, and bulbs need a small but continuous supply all winter long for strong growth of the foliage and the flowering bloomstalk.

For a long-lasting spring display, plant some early, mid-season, and late-blooming bulbs every other week from October through mid-December, and again beginning in late January.

Depth of planting also affects when the bulbs will bloom--shallower plantings will bloom sooner, and deeper plantings will bloom later. If you want everything to bloom for one spectacular display, plant the bulbs at the same time and at the same depth. If you prefer color over several months' time, plant bulbs every several weeks, and vary the planting depths each time you plant.

Plant autumn-blooming saffron crocus now for a November harvest. Each corm produces from one to three flowers, and about six corms should provide sufficient saffron--just the three tiny red stamens in each bloom--for each cooking or baking recipe.

Dry flowers for arrangements that you've grown yourself. The easiest to dry are baby's breath, bachelor's button, bells of Ireland, lavender, scabiosa, statice, strawflower, and yarrow. All but the bells of Ireland are best air-dried. Tie a few stems into a loose bunch, and hang it up, flower heads down, in a cool, dark, dry place for several weeks. The exception is bells of Ireland--stand these upright in a container with a half-inch of water; flowers will dry as the water evaporates.

Save the stalks of tall sunflowers, stripped of their branches and leaves, to use next year as trellises for peas and beans.

Start or reseed lawns. Keep the soil surface moist so seeds germinate and seedling roots get a good start. Feed and water established lawns; continue mowing at two inches in height.

Shrubs with colorful berries to plant now for fall and winter accents include abelia, barberry, bottlebrush, forsythia, holly, hydrangea, oleander, pyracantha, quince, and toyon.

This is the perfect time of year to plant a tree to beautify your yard--the roots will get well established before they go dormant, ready for the spring surge of both foliage and root growth.

Decide what you want from a tree--where it will be planted and for what purpose. If you want summer shade for the house, a deciduous tree planted on the south side would be appropriate. If you prefer a pleasant window view, a grouping of silver birches might be nice.

Fall colors come alive with many trees, including beech, birch, coral tree, gingko, liquidambar, magnolia, maidenhair, Japanese and other maples, crape myrtles, persimmon, Chinese pistache, sour gum, Chinese tallow, tulip tree (named for its tulip-shaped leaves), and zelkova.

Once you've made a preliminary choice, consider the mature size of the tree--does the area allow the tree sufficient space when it's mature? Have you planned for the different needs of the shaded and moist soil underneath its widespread limbs? When all these considerations seem to fit, purchase it and plant it.

Avoid choosing trees that are prone to wind damage. These include acacia, ash, cypress, elm, eucalyptus, liquidamber, California pepper, and pine.

Shape evergreen hedges for the last time this year.