What to Plant in Santa Cruz & the Bay Area in September
eptember in Santa Cruz County is still full-on summer in many areas. While days are getting shorter, temperatures are often at their hottest, regularly hitting the 90s and even 100s in inland valleys and sunny mountain areas. Coastal areas stay cooler but are still warm.
This is NOT yet fall weather, but it IS an important planting month. You're planting cool-season crops that will grow slowly in September heat, then take off when temperatures finally cool in October and November.
Why September Temperatures Matter
Don't let the calendar fool you. September is often our hottest month, especially inland:
Sunny mountain areas (Boulder Creek ridges, Ben Lomond chaparral, Scotts Valley hills): Regular 90 to 100 degree days, low humidity.
Under redwoods (Felton canyons, shaded Ben Lomond areas): 10 to 15 degrees cooler, more moisture retention.
Inland valleys (Scotts Valley, Soquel): High 80s to mid-90s.
Coastal (Aptos, Capitola, Santa Cruz): 70s to 80s, more stable temperatures.
Watsonville and Pajaro Valley: Mid-80s to low 90s.
You're still harvesting summer crops heavily, and tomatoes are absolutely still producing. In warm microclimates, they'll continue through October and even into November.
Direct Seed These in September
Cool-Season Greens
Lettuce: Choose heat-tolerant varieties for early September (Jericho, Muir, Nevada). Shade plantings from afternoon sun. Germination improves dramatically as the month progresses.
Arugula: More heat-tolerant than lettuce. Quick to germinate and produce. Will bolt faster in heat but still worth planting.
Spinach: Late September is better than early. Bloomsdale Long Standing handles heat better than most varieties.
Mustard greens: Fast-growing and surprisingly heat-tolerant. Red Giant and Mizuna are good choices.
Chard: Bright Lights and Fordhook Giant establish well even in September warmth. More heat-tolerant than most greens.
Mizuna: Mild Japanese green that handles warmth reasonably well.
Asian greens: Bok choy and tatsoi prefer late September when temperatures moderate slightly.
Mâche (corn salad): Wait until late September. This cool-weather specialist struggles in heat.
Root Vegetables
Radishes: Quick 30-day varieties give you fast results. Cherry Belle and French Breakfast are reliable even in warmth.
Turnips: Hakurei and Tokyo Cross are mild, sweet varieties. Plant all month.
Beets: Detroit Dark Red and Chioggia establish well. Keep soil consistently moist for germination.
Carrots: Plant all month for fall and winter harvest. Nantes and Danvers types are reliable. Consistent moisture is critical for germination.
Legumes
Peas: Late September in cooler areas (coastal, under redwoods). Sugar snap and snow peas planted now establish over fall and produce in spring.
Fava beans: Late September works, though October is traditional. These nitrogen-fixers also make excellent cover crops.
Herbs
Cilantro: Finally won't bolt immediately in the cooler days ahead. Direct seed for fall harvest.
Dill: Quick to germinate and produce. Let some go to seed for self-sowing.
Parsley: Both flat-leaf and curly establish well. Slow to germinate, so be patient.
Cover Crops
If you have empty beds, plant cover crops now:
Fava beans: Fix nitrogen and produce edible beans. The best all-around cover crop for our area.
Crimson clover: Beautiful red flowers in spring, fixes nitrogen, attracts pollinators.
Winter vetch: Good nitrogen fixer, combines well with other cover crops.
Transplant These in September
Brassicas (from July and August Starts)
Broccoli: Transplant early September for fall harvest. Needs warm days to develop heads.
Cauliflower: Same timing as broccoli. Later transplants may not head up before winter.
Cabbage: More forgiving than broccoli. Can transplant through mid-September.
Kale: Transplant all month. Lacinato and Red Russian are excellent fall varieties.
Collards: Heat-tolerant and forgiving. Transplant anytime in September.
Other Transplants
Lettuce: Give afternoon shade in early September. Easier to establish as the month progresses.
Onions: From sets for spring and summer harvest. They'll develop roots over fall and winter.
Strawberries: Excellent month for planting. Plants establish during fall rains and produce heavily next spring.
What to Harvest in September
Peak summer harvest. September is NOT winding down yet:
Tomatoes: Still going strong in most microclimates. This is peak season, not the end.
Peppers: Peak production continues. Harvest regularly to encourage more fruit.
Eggplant: Still producing in warm areas.
Summer squash and zucchini: Ongoing harvest if you've managed powdery mildew.
Beans: Late plantings are producing. Succession planting pays off now.
Cucumbers: May be winding down but still productive.
Melons: Late varieties are ripening.
Early fall greens: Lettuce, arugula, and kale from July and August plantings are ready.
Apples and pears: Tree fruit season continues.
September Garden Tasks
Continue harvesting summer crops heavily. This is peak season, not the end.
Direct seed fall greens and root vegetables for fall and winter harvest.
Transplant brassicas that you started in July and August.
Plant strawberries. September is an excellent month for establishing new strawberry beds.
Succession plant beans and summer squash if you're in a warm microclimate. You have time for another round.
Water deeply. September is still dry and hot. Don't reduce irrigation yet.
Shade new plantings of cool-season crops from afternoon sun until they establish.
Start planning fall garden but don't pull summer crops that are still producing.
Save seeds from heirloom tomatoes and peppers for next year.
Order garlic for October planting. Popular varieties sell out.
Microclimate-Specific Advice for September
Coastal (Aptos, Capitola, Santa Cruz, Live Oak)
You have the most stable temperatures, warm but not extreme (70s to 80s). September is excellent for planting cool-season crops. Your tomatoes are still producing but may slow down earlier than inland areas. Plant everything on the list. Fog has largely cleared but afternoons are pleasant. Less need for shade cloth than inland gardens.
San Lorenzo Valley Sunny Ridges (Boulder Creek, Ben Lomond, Scotts Valley Hills)
You're experiencing 90 to 100 degree days regularly. Summer crops are thriving. Don't pull them. Your tomatoes will produce through October and possibly into November. Plant cool-season crops, but give them afternoon shade and consistent water. They'll grow slowly now but take off in October. You have huge temperature swings from day to night (sometimes 40 degrees).
San Lorenzo Valley Shaded Areas (Felton, Ben Lomond Canyons)
You're 10 to 15 degrees cooler than sunny ridges nearby, maybe high 70s to mid-80s. Better conditions for cool-season crops. You may have more moisture retention from morning fog and shade. This is a great time to plant greens and brassicas. Less temperature swing than sunny areas means less plant stress.
Inland Valleys (Scotts Valley, Soquel Hills)
High 80s to low 90s, similar to sunny mountain areas. Still hot. Summer crops are producing well. Plant cool-season crops with shade and good watering. Don't expect fall conditions yet.
Watsonville and Pajaro Valley
Mid-80s to low 90s, warm and sunny. Your agricultural climate means excellent conditions for both late summer crops AND fall plantings. You have the longest season in the county. Take advantage of it. Tomatoes will produce well into November here.
Heat Management for September Plantings
Since you're planting cool-season crops in summer heat, you need strategies:
Shade new plantings from afternoon sun. Shade cloth, lattice, or even a propped-up board on the west side helps tender seedlings survive.
Water consistently. Soil is still drying out quickly. New plantings need daily attention until established.
Choose heat-tolerant varieties of lettuce and greens for early September. Jericho lettuce was bred for hot climates.
Wait until late September for truly cold-hardy crops like mâche and spinach.
Pre-sprout seeds indoors before planting if germination is a problem. Start seeds in a cool location, then transplant sprouts.
Mulch heavily to keep soil cooler and retain moisture. Straw works well around seedlings.
Local Resources for September Gardening
Seeds and Transplants
Renee's Garden Seeds (based in Felton) carries heat-tolerant lettuce varieties and fall vegetable seeds suited to our climate.
Sierra Azul Nursery (2660 E. Lake Avenue, Watsonville) has fall vegetable transplants including brassicas and greens.
San Lorenzo Garden Center (808 River Street, Santa Cruz) stocks seasonal vegetable transplants and strawberry plants.
Mountain Feed & Farm Supply (9550 Highway 9, Ben Lomond) carries cover crop seeds and fall planting supplies.
Strawberry Plants
Peaceful Valley Farm Supply (ships to Santa Cruz) has excellent bare-root strawberry selection for fall planting.
Education
UC Master Gardeners of Monterey Bay offer fall workshops and can answer questions about managing the summer-to-fall transition.
Frequently Asked Questions About September Gardening
Is it too late to plant tomatoes?
In warm microclimates (sunny mountain areas, Watsonville), tomatoes planted in early September can still produce before frost. But you need fast-maturing varieties (Early Girl, Stupice, cherry types) and transplants, not seeds. Coastal gardeners are pushing it, but inland gardeners have time for one more round.
Should I pull my tomato plants?
Absolutely not, unless they're diseased or you desperately need the space. September tomatoes are at their peak in most areas. In warm microclimates, they'll keep producing through October and even into November. Let them produce. This is the question I get asked most often, and the answer is almost always "wait."
Why aren't my lettuce seeds germinating?
It's too hot. September soil temperatures are still in the 70s to 80s, which is above ideal germination temperatures for lettuce (60 to 65 degrees). Try pre-sprouting seeds in a cool indoor location, planting in afternoon shade, or waiting until late September. Coastal gardeners have better luck than inland gardeners.
Is it too late to plant broccoli?
Early September with transplants? You're fine. Late September? You can still plant kale and collards, but broccoli and cauliflower might not have enough warm days to form heads before winter. These crops need approximately 60 to 80 days of reasonable growing weather to produce heads.
When should I plant garlic?
October is traditional, but late September works in warmer areas. Wait for the heat to break slightly. Garlic planted in very warm soil can rot. Most gardeners wait until early to mid-October to be safe.
How do I keep lettuce seeds cool enough to germinate?
Pre-sprout seeds indoors where it's cooler, then transplant the tiny sprouts. Or plant in the evening, water well, and cover with a board or shade cloth to keep soil cool. Remove covering as soon as you see green. Mulching around (not on top of) seeds helps keep soil cooler too.
Can I plant strawberries in September?
Yes, September is actually an excellent month for planting strawberries. Plants establish during fall rains, develop strong root systems over winter, and produce heavily the following spring. Plant bare-root or potted plants. This is often better timing than spring planting.
What if my summer crops are still producing heavily?
Keep harvesting them. There's no rule that says you must transition to fall crops on a schedule. If tomatoes, peppers, and squash are still producing, let them continue. Plant fall crops in any empty space, or wait until plants genuinely finish. In warm microclimates, summer crops often produce into November.
Free Gardening Resources
Seasonal Planting Calendar — Month-by-month planting guide for Santa Cruz County, including September's dual-season approach.
Vegetables by Season — Quick reference for which vegetables to plant in the summer-to-fall transition.
Know Your Microclimate Worksheet — Identify your specific growing conditions to understand September temperatures in your location.
Tomato Variety Selector — Choose fast-maturing varieties for late-season planting.
The September Reality Check
Most gardening advice says "September is fall." Not in Santa Cruz County. September is:
Still summer temperatures (often our hottest month inland)
Peak harvest for summer crops
Planting time for fall crops (that will grow slowly until October and November)
Continued need for irrigation and pest management
NOT the time to pull productive plants
You're simultaneously harvesting summer crops at their peak, planting fall crops that will grow slowly now but rapidly later, still dealing with summer heat and dry conditions, and preparing for the eventual arrival of fall weather in late October or November.
Don't rush to pull summer plants. Don't expect fall weather. Work with the heat you have, and trust that your fall plantings will take off when cooler temperatures finally arrive.
