By Season: Autumn in Your Garden
What to Do in September / October / November
- Plant bulbs for spring
- colorful fall flowers: pansies, violas, mums, stock, snapdragons, cyclamen.
- cool season vegetables: garlic cloves (2 inches deep and 3 to 6 inches apart)
- Fertilize azaleas, camellias and rhododendrons with fertilizer for acid-loving plants.
- Pull up veggie plants that are no longer producing; compost only those that show no sign of disease. Add disease free garden waste, grass clippings, pruning material and leaves to compost.
- Turn compost to keep it moist. Cover before rains start to retain moisture; cover during rainy weather to avoid the pile becoming waterlogged.
- Check drainage systems.Install downspout diverters to direct runoff to landscape trees and plants. Watch for standing water near tree trunks and the root zone of trees; divert all standing water.Refresh the spring application of mulch to bring it to a depth of 2-3 inches.
- Clean and disinfect pruning shears that contact infected plants. Air dry and oil shears immediately after use to avoid corrosion.
- Organize tool shed and inventory supplies for the upcoming season.
- Manage weeds in the rainy season before they flower, using non-chemical methods such as cultivation, hand weeding, or mowing. Use toxic chemicals only as a last resort.
- Take all recommended steps to maintain fire safety. Fire danger remains high during dry, hot months.
- Plant California natives so they can get established through the winter months. Check the UC Davis Arboretum All Star plant database for ideas. The California Native Plant Society (CNPS) website is another great resource.
- Reduce the watering time on irrigation controllers monthly by 25%. Consider turning off irrigation controllers if rain is adequate. New plantings should be irrigated on a regular basis until they have become established. Comprehensive information about water conservation in irrigation is available through the University of California’s Water Use Classification of Landscape Species (WUCOLS).
- Avoid working wet soil or using heavy equipment on wet soil, which can cause poor aeration and compaction.
- Add fallen leaves and plant debris to your compost pile, or leave them on the ground to serve as natural mulch.
- shrubs, trees, and perennials before arrival of winter rains, which help new plantings to establish strong root systems.
- cool-season vegetable seedlings including cabbage, kale, chard, and spinach. Carrots may be seeded now.
- Remove dead or diseased limbs from trees and shrubs.
- Clean thoroughly garden tools for the winter, before you put away. Rub with alcohol or disinfectant spray after each use to prevent the spread of disease. Prevent rust with a light coating of lubricant such as lithium grease.
- Control slugs and snails with organic slug bait that is safe for use around animals and food. Always read product labels carefully.
- Protect sensitive plants from cold injury when frost is predicted. Average first frost dates in San Mateo and San Francisco Counties may occur around November 30; average last seasonal frost usually occurs between late January and late February.
Dig Deeper for Autumn Edibles
Plan: Record information for next season, including where warm season vegetables were planted and how they fared. Begin to plan your cool season spring garden, and order seeds early. And this is a good time of year to order a soil analysis. Contact the Master Gardeners for a list of references.
Soil: Develop a plan to care for your soil after harvest by planting one or more cover crops to improve soil microbes, fertility and tilth. Find out more here.
Plant: Check the vegetable planting guide for our region. Consider the full range of edible planting options through this month-by-month guide, from fall through next summer. (link takes us to the sunny guide only - need others?)
Feed Plants: Stop feeding as weather cools, because plants are slowing their growth or going dormant. Feed fruit trees after harvest with an appropriate fertilizer, following application rate for your product.
Protect: Watching for frost warnings (mid Nov). If a frost is predicted, protect citrus, sub-tropical and tender plants; keep the root zone moist but not soggy. After mid- November, some trees may need to be covered. If temperatures fall below 50°, cover outdoor seedlings.
Prune: Remove dead, diseased, broken branches. Improve tree structure by opening the canopy to bring sun and air circulation to the tree’s interior.
Note: Apricot and cherry trees are the exception; prune these in July/August only. Just follow these steps.
Harvest: Harvest mature cool season vegetables started in summer. Not sure if something is ready? Wondering about proper storage of freshly harvested fruits and vegetables? This link will help.
Clean-up: Control overwintering pests by removing fruit mummies and fallen leaves on the ground under fruit and nut trees, especially if codling moth is a problem. Dispose in green yard waste bin; composting this material could reintroduce pests/pathogens.
What to Do for Autumn Landscape
Plant: California natives, bare root deciduous trees, shrubs and vines (e.g. cane berries), fruit and nuts, grapes, and roses. Select species and cultivars well-adapted to the local site. Sow native meadow flowers, spring blooming flowers and grasses. Plant spring blooming bulbs. Plant cool season annuals for color (Iceland poppy, viola, pansy, ornamental kale, etc.). Water regularly to keep each root zone moist, but not soggy. Check out Katherine Jones article on selecting fruit, nut and berry crops. If you’re planting California native plants, consider using this interactive garden planning guide from the California Native Plant Society.
Propagate: Direct sow summer and fall annuals (cosmos, marigolds, nasturtiums, etc.) when soil temperatures are at least 70°. Divide or transplant hardy perennials (aster, chrysanthemum, hosta). Divide spring flower bulbs (daffodils, Pacific Coast iris, tulips, etc.).
Feed Plants: As plant growth slows or plants go dormant, stop adding fertilizer.
Protect: If frost is predicted, water your plants, keeping the root zone moist but not soggy. Cover frost-tender species as appropriate (bougainvillea, hibiscus and succulents).Clean-up: Clean up leaf debris for composting or yard waste pick up. Leaf debris (from non-diseased plants and trees) can be used as mulch on unprotected soil if plants are not susceptible to fungi.
Prune: Prune evergreen, summer-flowering shrubs in September. Prune deciduous trees and shrubs that need pruning such as crape myrtle, rose, and spirea in October. Make cuts properly to encourage good form and structure.
Do not prune evergreen trees during fall, since wound closure is 20% slower. Remove dead, diseased, and borer-infested wood.
Maintenance: Clean up fallen leaves and blossoms from the area below and around your plants. Do not compost diseased material.
Deep water trees adapted to summer rainfall (e.g. fruit and nut trees). Paint trunk and scaffolds with white interior latex paint diluted with an equal amount of water. Prepare for rainfall. Prevent water ponding around trunks and foundations. Improve drainage. Install downspout diverters to direct runoff into landscape soils, but avoid water-logging of soil.
Autumn Pests and Diseases
- Aphids, borers and spider mites (September), yellowjackets (September-October), ants (September-November), carpenter bees (October-November)
- Leaf Footed bug – Inspect almonds, pistachios, and pomegranates (September)
- Borers – Fruit and nut trees (September)
- Apple and pear trees – Codling moth (September)
- Citrus – Asian citrus psyllid (when new leaves are forming), leafminer (September-November), snails (October-November)
- Coast redwood dieback – Check for drought-stress related pests such as bark beetles and spider mites (September-October).
- Pine – Bark beetles, pitch moths, wood borers (October-November)
For comprehensive information on pest identification in home and garden, along with pesticide use and alternative solutions, refer to UC Integrated Pest Management.
- Root rot (September-November)
- Cankers (September)
- Coast redwood dieback – Check for drought-stress related maladies such as abiotic disorders and fungal diseases (September-October).
- Citrus – Brown rot, root rots (October-November)
- Olive – Olive peacock spot or scab (October); olive knot (November)
- Pine – Western gall rust (October-November)
- Stone fruits – Monitor for leaf curl or shot hole of apricot, nectarine, peach and plum (November)
For further information plant disease identification and solutions, refer to the UC IPM Disease Menu
A portion of this Autumn garden checklist was originally developed by Contra Costa County Master Gardeners. Content has been expanded and adapted to San Mateo and San Francisco Counties.