By Season: Summer in Your Garden
What to Do in June / July / August
- Clean: dead flowers, fallen fruit, leaves and nuts to discourage fungal growth and pests.
- Plant: beans, cucumbers, eggplant, peppers, pumpkins, summer squash and tomatoes
- Check irrigation systems by turning them on and inspecting them to make sure everything is working properly.
- Clean out clogged heads and replace broken heads.Warm weather plants need consistent irrigation throughout the growing season.
- Adjust watering schedule, according to the weather and changing needs of your plants. The water requirements of your plants peak in July and are high in August. Pay close attention to the moisture needs of new plants in your garden. Established perennials, shrubs and trees need infrequent but deep watering. For more detailed information, check the Bay Area Watering Guide
- Water when temperatures are cooler and air is still, usually in the early morning. Water deeply to moisten the root zone, but not deeper. Container plants may need daily watering, as soil in pots can dry out quickly and damage plant roots on hot summer days
- Feed tomato plants with a low-nitrogen fertilizer when fruit starts to develop (too much nitrogen encourages more foliage and less fruit).
- Mulch tomato plants to conserve moisture.
- Apply 2-3” of mulch where existing mulch is thin or soil is bare, to protect against heat and water stress in growing roots.
- Keep mulch back 12” from tree trunks and 6” from perennials to discourage pathogens.
- Apply ½ to 1” of compost around landscape plants and work in lightly, followed by a layer of mulch.
- Garden tools:
- Sharpen pruning shears and other garden tools, as needed.
- Clean and disinfect your pruning shears after use.
- Finish with a light coat of oil to protect the blades.
- Use non-chemical methods such as cultivation; use toxic chemicals as a last resort.
- Hand weeding, or mowing;
- Identify weeds in your garden by knowing the four categories of weeds: broadleaf, grass, sedge, aquatic
- Wildfire is an ever-present danger in California during dry months. Learn more about firewise safety practices to maintain your garden and landscape.
- Pick up and dispose of any fallen fruit and vegetables to avoid spreading fungus spores and to prevent invasions of pests.
- Deadhead fading flowers to encourage new blooms.
- Prop up limbs of heavily-laden fruit trees to prevent broken branches.
- Grow herb seedlings in well-draining soil in a location that gets 4-6 hours of sun each day.
- For tomato plants that produce large slicing tomatoes, thinning fruit will encourage plants to produce larger tomatoes. This will also reduce weight on fragile branches.
- Water mature trees deeply, especially during drought.
- To maximize the numbers of blooms on dahlias, cut back the center stems to encourage more lateral branches.
- Cactus and succulents are drought tolerant but many appreciate some water in very hot weather. Succulents may find full sun to be too strong in some locations, so provide them with shade if they seem to be struggling.
- Mulch garden and vegetable beds to protect them from summer heat, reduce watering needs, and keep weeds down.
- If you have whiteflies, control them with sticky traps and increase air circulation by thinning out dense branches and foliage.
- Keep compost turned and moist, adding greens and browns as needed.
- This is the month to fertilize everything in the landscape that is blooming or budding, especially fuchsias, begonias, and roses. If soil is dry, water well before fertilizing.
- Maintain drip irrigation systems for most effective water use; check for leaks and missing or broken emitters.
- Continue sowing seeds for cool-season crops including beets, turnips, cabbage, radishes, broccoli, peas, kale, collard, spinach, arugula, and lettuces.
- Water citrus trees in containers once a week or more often in hot weather.
- Remove runners from strawberries to encourage buds for next year and to strengthen the plant.
- Plan your vegetable garden for crop rotation to avoid replanting the same types of plants - especially Tomato and Pepper in the same area for two consecutive seasons. If you don’t have enough room to rotate, carefully remove any “sick” plants from your garden and consider growing disease resistant plant varieties.
- Prune fruit trees to control height, maintain shape, and eliminate suckers.
- This is the month to plant autumn bulbs such as autumn-flowering crocus (Crocus speciosus), meadow saffron (Colchicum autumnale), and spider lilies (Lycoris).
- Fertilize azaleas, camellias, hydrangeas, and rhododendrons with an acid type fertilizer. Use all-purpose fertilizer for all plants in bloom.
- Prune berry vines after fruit is harvested.
Dig Deeper for Summer Edibles
Plan: Order seeds for cool season vegetables.
Soil: Before planting any vegetable crops, add a 1” layer of compost or high quality organic material to the bed, work the amendments into top 4” of soil. Water the bed evenly but do not over-water; let the bed rest. At the time of planting, add organic fertilizer to planting hole depending on the feeding needs of your vegetables (light, medium or heavy). Lightly work fertilizer into planting holes.
Plant: Soil temperature is no longer a concern, but air temperature is. Continue to check the vegetable planting guide for your area in San Francisco or northern San Mateo counties. Near the coast, sow these seeds: carrots, beets, spinach, chard, arugula and parsley; plant these plants: Florence fennel, radicchio, escarole, broccoli, kale, collards, Brussels sprouts, cauliflower and cabbage. NEED LINK TO FOGGY and SUNNY AREAS
- Acid-loving fruits – Use an acid fertilizer; follow application rate and instructions for your product. (Blueberries require two applications in summer.)
- Citrus – Test soil. As needed, apply fertilizer high in nitrogen and/or supplement with iron. (June)
- Caneberries and deciduous fruit trees (two applications in summer).
- Vegetables – Heavy-feeding vegetables will need a nutritional supplement, e.g. tomato plants benefit from a low-nitrogen fertilizer when fruit starts to develop.
Protect: Cover crops with shade cloth to protect from hot midday sun; cover fruit trees and grapes with netting to exclude birds and other vertebrate pests.
Prune: Prune cherry trees in July/August and apricot trees in August. Other fruit trees may be pruned as soon as they finish producing, especially if managing height. If growing caneberries, cut two-year-old canes (floricanes) to the ground right after harvest. Remove suckers from all fruit trees.
Train: Stake or cage large plants as needed to keep them upright.
Harvest: Harvest mature warm season vegetables. Not sure if it’s ready to harvest? Check the vegetables section of the California Garden Web.
What To Do For Summer Landscape
Plan: Order spring-blooming bulbs now for best selection (August).
Plant: Sow seeds of fall-blooming annual flowers directly in the ground; keep bed moist until seedlings emerge.
Feed plants if needed: Determine nutritional needs (N-P-K and pH) of landscape plants.
- Feed roses and other flowering plants to keep them blooming (June).
- Feed azaleas, camellias, gardenias, rhododendrons and other plants adapted to acidic soil using an acid fertilizer.
- Feed cymbidium orchids (every week to two weeks), and other container plants.
Remember, fertilizer should feed the soil, not the plants
Maintenance: Treat ponds with mosquito repellent. Raise the cutting height of your lawnmower 1 to 1.5” to help grass survive drought and heat (encourages deep roots and reduces water demand). Leave clippings on the ground for nutrients and as a mulch layer.
Propagate: If not done in spring, on a cool day dig up and divide overcrowded spring-blooming perennial bulbs (daffodils, daylilies, iris and tulips) and trim dead portions. Store in a cool, dry place for replanting in fall. Start seeds of cool season annuals, such as calendula, stock, etc. (August)
Train: Stake tall plants such as gladiolas, lilies & vines (June).
Protect: To reduce fire hazard, keep wild grasses and weeds mowed, leaving a 30-foot swath (where possible) around your property; trim dead growth from shrubs and trees, and prune any branches that overhang the eaves. Remove leaves and debris from the roof.
Summer Pests and Diseases
- Ants, aphids, borers, carpenter bees, carpenterworm, mosquitoes, spider mites, yellowjackets (June-August); scale insects (June)
- American plum borer – Check for frass and gum on lower branch crotches and graft unions of young trees such as almond, mountain ash, olive, sycamore, and stone fruit (June-July)
- Cherry spotted wing drosophila – Inspect cherry, raspberry, blackberry, blueberry, and strawberry crops (June)
- Clearwing moths – Look for signs of boring in ash, birch, pine, poplar, and willow; less often in oak, sycamore, and stone fruits (June-July)
- Green fruit beetle – Check fig and stone fruits (July)
- Leaffooted bug – Check fruits and nuts such as almonds, pistachios, and pomegranates (June-August)
- Redhumped caterpillars – Check trees such as liquidambar, redbud, stone fruits, and walnut (June-August)
- Apple and pear trees – Look for codling moth and Fire Blight (June-August)
- Citrus – Check for Asian citrus psyllid (when new leaves are forming), leafminer (June-August), and scales (June)
- Coast redwood dieback – Check for drought-stress related pests such as bark beetles and spider mites (June-August)
- Roses – Watch for hoplia beetle and thrips (June)
For further information, refer to UC IPM Pest Notes
- Bacterial blast, blight and canker – Inspect apple, citrus and stone fruit (July-August)
- Fire blight – Look for oozing and dead limbs on pome plants such as apple, crabapple, pear & pyracantha (June-July)
- Eutypa dieback – Look for cankers, limbs or twigs wilting on apricot and cherry (August)
- Powdery mildew – Inspect apple, crape myrtle, grape, rose, and stone fruits (June-August)
- Coast redwood dieback – Check for drought-stress related maladies such as abiotic disorders and fungal diseases
- Roses – Watch for black spot (June), powdery mildew (June-August)
For further information, refer to the UC IPM Disease Menu
A portion of this Summer garden checklist was originally developed by Contra Costa County Master Gardeners. Content has been expanded and adapted to San Mateo and San Francisco Counties.