September Garden Tips
Welcome to Garden View’s monthly gardening tips. We hope you find this information useful and check back often as we will feature new tips each month as well as new articles to the right.
September can still feel like summer in Southern California, especially when Santa Ana winds arrive. This is a transition month: protect plants from heat and wind, keep watering deep, clean up summer growth, and begin preparing beds for fall planting.
As the season shifts, avoid pushing too much tender new growth on plants that need to harden off before winter. Focus on light pruning, selective cleanup, soil preparation, mulching, and planting cool-season flowers and vegetables.
Deep-water before hot, dry winds; prune selectively; prepare soil for fall planting; and start winter-spring flowers and vegetables.
Pruning, shaping, and plant care
Brazilian and California Pepper Trees
Remove suckers and thin upright growth for a graceful form.
Brazilian pepper (Schinus terebinthifolius) and California pepper (Schinus molle) both look better when suckers are removed regularly. If suckers are left alone, these trees can become wide, invasive-looking, and shrub-like.
Thin upright-growing branches to encourage the softer, weeping form that makes pepper trees attractive.
Evergreen Pears
Remove fire blight damage carefully and sterilize between cuts.
To slow fire blight, remove dead-looking branches and twigs. Cut about a foot below visible damage and sterilize clippers between cuts with a diluted chlorine solution or another sterilizer.
Outside of removing diseased wood, prune evergreen pears minimally if you want more blooms.
Ficus pumila / Ficus repens — Creeping Fig
A beautiful wall vine, but it must be controlled.
Creeping fig is common in Southern California and attaches itself to walls and buildings. It grows in sun or shade and is excellent for blank walls, but it can become invasive and damage wood, windowsills, or planters if left unchecked.
Prune often to keep the small, attractive leaves. If left unpruned, vines and leaves become larger and less refined. Creeping fig can handle severe pruning when needed, even down near the ground, which encourages fresh juvenile growth.
Roses
Clean up sprawling growth and remove suckers.
September is a good time to cut back tall, sprawling stems and reshape roses that have gotten leggy. You can safely reduce roughly one-third of the plant if needed.
Remove suckers regularly. Pulling them off with a firm downward and forward tug often prevents them from regrowing better than a clean cut.
Silk Floss Trees (Ceiba speciosa, formerly Chorisia speciosa)
September is bloom season; reduce watering to encourage flowers.
Silk floss trees are known for green trunks, trunk spikes, and showy fall bloom. Cut back on watering in August and September to encourage heavier flowering.
Once established, these trees can often do well with occasional deep watering and only light pruning.
Hibiscus
A light feeding can extend bloom, but don’t overdo it.
Hibiscus can use a light dose of fertilizer to help prolong bloom. Avoid overfeeding or overwatering; vigorous, soft growth is more prone to whitefly problems.
Tip pinching in spring and summer increases bloom, and removing about one-third of old wood in early spring keeps plants vigorous. In September, stop pruning soon so plants can harden off for winter. If necessary, give one last light trim now, then stop for the season.
Avocado and Citrus Trees
Mid-September is a good window for light pruning.
Light pruning a couple times a year is better than heavy pruning. Remove vigorous upright water sprouts now, then prune again in March if needed.
Bloody Cranesbill (Geranium sanguineum)
Cut back hard for a compact winter plant and improved bloom.
Cut back now to encourage new growth, increase bloom, and keep the plant compact heading into winter.
Crape Myrtle Trees (Lagerstroemia indica)
Remove suckers to reduce stress and mildew-prone growth.
Crape myrtles are low-water, long-flowering trees with minimal maintenance, but trunk suckers should be removed promptly. If suckers are allowed to grow, the tree can become more prone to powdery mildew, especially when growing in a regularly watered lawn.
Sycamores, Fruit Trees, and Summer Leaf Drop
Leaf drop during heat is often a natural stress response.
Sycamores, fruit trees, and many other trees may drop leaves during extreme heat when they cannot move enough water from the soil to the leaves or fruit. This is often natural. Fewer fruit can also mean larger fruit at harvest.
Adding more water may not always help immediately. Trees grown with frequent shallow watering may have smaller root systems and can be more likely to show heat stress. Most large trees benefit from occasional deep watering to encourage deeper roots and better water storage.
Agapanthus — Lily of the Nile
Heat fading is common and usually temporary.
Agapanthus is one of Southern California’s favorite plants: attractive most of the year, durable, water-wise, and beautiful in late spring and early summer bloom. In full sun and extreme heat, leaves may fade or scorch where they bend. This is usually temporary and may only last a month or two.
Flaxes (Phormium)
Leave scorched leaves until the heat has passed.
Many flaxes show heat scorch in September. Leave scorched leaves in place until temperatures ease because they help protect the leaves underneath. Remove dead lower leaves as usual.
What Is Rolling Up the Sod?
Raccoons, skunks, and other animals may roll new sod looking for grubs and earthworms.
This is common in mid- to late summer, especially with newly laid sod and excessive watering. Extra moisture brings grubs closer to the surface, making the sod more attractive to animals.
Turning down the water can make a big difference. If grubs are part of the problem, use a labeled lawn grub control according to directions.
Lavender (Lavandula)
Shear after bloom and avoid rich, wet soil.
Lavender prefers well-drained soil and very little fertilizer. To keep plants compact, shear back one-third to one-half immediately after bloom.
If plants become woody, remove a few of the oldest branches and watch for new growth. If they do not respond, replacement is usually best. Gravel is often better around lavender than compost.
New Zealand Tea Tree Shrubs (Leptospermum)
Do not prune in fall if you want spring bloom.
Leptospermum blooms beautifully in spring, and fall pruning can reduce flower abundance. This is a low-water, easy-care plant when grown in well-draining soil.
Avoid overwatering in clay soil; root rot can become a problem.
Honeysuckle (Lonicera sempervirens)
Prune heavily in early spring and again after flowering.
Honeysuckle blooms from late spring through much of summer. Prune heavily in early spring, then prune again at the end of flowering in September.
Potted Succulents
Feed lightly with diluted liquid fertilizer.
Use a well-diluted liquid fertilizer for potted succulents. Avoid overfeeding and make sure containers drain well.
September garden tasks
Amend Soil for Planting
Spade or rotary-till plenty of organic matter into beds before planting. Good soil preparation now helps fall plantings establish faster.
Feed Many Plants
After setting out fall flowers and vegetables, wait about two weeks before feeding with diluted or granular high-nitrogen food. Continue feeding fuchsias and begonias once or twice a month.
Fertilize new shrubs, trees, and groundcovers about a month after planting, then wait until spring to feed again.
Groom Flowering Plants
Pick faded flowers from begonias and dahlias. Cut back leggy geraniums and pelargoniums for better form next spring. Prune marguerites back by about one-third to force compact new growth.
Mulch
With summer-like temperatures still possible, thicken mulch layers to cool roots, conserve moisture, and suppress weeds. Use ground fir bark, peat moss, straw, hay, or compost.
Take special care to mulch newly planted items.
Water Before Santa Ana Winds
If hot, dry Santa Ana winds threaten, deep-water before the wind event. Water during cool morning or evening hours to reduce evaporation losses.
Planting in September
Plant Fall-Blooming Bulbs
For very quick color, plant autumn crocus (Colchicum autumnale) corms and spider lily (Lycoris) bulbs. They can bloom almost immediately. Fall-blooming true crocus species may also be available.
Plant Landscapes
Set out hardy evergreen and deciduous shrubs, trees, and groundcovers. Plant cool-season lawns from sod or seed. Water new plantings regularly until winter rain arrives.
Plant Spring-Blooming Bulbs
Many Dutch-grown bulbs arrive in nurseries this month. For best selection, buy crocus, daffodils, hyacinths, grape hyacinths, and tulips early.
Chill tulips and other bulbs that require chilling in a paper bag in a 45-degree refrigerator for about six weeks before planting. South African bulbs such as freesia, ixia, sparaxis, watsonia, and ranunculus also begin arriving.
Plant Winter-Spring Flowers
For garden color from Thanksgiving through spring, set out seedlings of calendula, candytuft, cineraria, delphinium, English daisy, foxglove, Iceland poppy, nemesia, pansy, penstemon, snapdragon, stock, sweet William, and violas.
You can still start seeds in flats for transplanting in 4–8 weeks. Keep young seedlings evenly watered during hot weather.
Plant Winter Vegetables
Sow seeds or set out seedlings of beets, broccoli, Brussels sprouts, cabbage, cauliflower, carrots, celery, chard, chives, collards, kale, kohlrabi, leaf lettuce, onions, parsley, parsnips, peas, radishes, spinach, and turnips. In very hot areas, shade young plants for a few days until established.
Welcome to Garden View’s monthly gardening tips. We hope you find this information useful and check back often as we will feature new tips each month as well as new articles below.