If you’re a gardener in Northern California, figuring out when to plant broccoli can be the difference between tight heads and bolted flowers. Knowing the optimal timing for planting is your first step to a great harvest.
Our climate is unique, with coastal fog, hot valleys, and mountain chill. This guide will help you nail the schedule for your specific area. You’ll learn how to work with our seasons for the best results.
When to Plant Broccoli in Northern California – Optimal Timing for Planting
The perfect planting time depends on whether you’re starting from seed or transplants. It also hinges on your local microclimate. Generally, you have two main planting windows: late winter for a spring crop and mid-to-late summer for a fall crop.
Understanding Your Northern California Microclimate
Northern California isn’t one place. Your planting dates shift based on where you garden.
- Coastal Areas (SF, Monterey Bay): Mild year-round. You can often plant spring crops earlier and fall crops later. Frost is rare, but summer heat is limited.
- Inland Valleys (Sacramento, San Joaquin): Hot, dry summers and cooler winters. Timing is critical to avoid peak summer heat, which causes bolting.
- North Coast & Mountain Areas: Shorter growing seasons with more frost. You’ll rely on the summer window and need frost protection.
Spring Planting Schedule
For a spring harvest, the goal is to get broccoli established in cool weather and harvested before the summer heat arrives.
- Start Seeds Indoors: Begin 6-8 weeks before your last average frost date. For many valleys, this is early January. On the coast, you can start as early as late December.
- Transplant Outdoors: Move seedlings into the garden 2-4 weeks before the last frost, when they have 4-6 true leaves. This is typically late February to March. Harden them off first!
- Direct Seed (Risky for Spring): You can sow seeds directly in late January or February if soil is workable, but transplants give you a head start.
Spring planting can be tricky. If a late heatwave hits, your broccoli might bolt prematuely.
Fall Planting Schedule (The Easier Option)
Fall is often the best time for broccoli in Northern California. Growing conditions improve as temperatures fall.
- Start Seeds Indoors: In mid-to-late June for inland areas, or early-to-mid July for coastal spots. This protects young plants from intense heat.
- Transplant Outdoors: Aim for late July through August. The seedlings will grow as the days shorten and cool.
- Direct Seed: You can sow seeds directly in the garden in early July for inland areas, or late July for coastal. Keep the soil consistently moist for germination.
The fall crop matures in cooler weather, which improves flavor and head development. You’ll often get a larger, more reliable yeild.
Step-by-Step Planting Guide
1. Preparing Your Soil
Broccoli needs fertile, well-draining soil. A few weeks before planting, work in 2-3 inches of compost. Broccoli is a heavy feeder, so also mix in a balanced organic fertilizer according to package directions. The soil pH should be slightly acidic to neutral (6.0-7.0).
2. Planting Your Broccoli
- Space transplants 18-24 inches apart in rows 2-3 feet apart. They get bigger than you think!
- Plant them at the same depth they were in their pot. Firm the soil gently around the stem.
- Water deeply immediately after planting to settle the roots.
3. Essential Care Tips
- Watering: Provide 1-1.5 inches of water per week. Consistent moisture is key to prevent tough stems and bolting. Drip irrigation is ideal.
- Mulching: Apply a 3-inch layer of straw or shredded leaves around plants. This conserves moisture, keeps roots cool, and suppresses weeds.
- Fertilizing: Side-dress with a high-nitrogen fertilizer 3 weeks after transplanting and again when heads begin to form.
- Pest Watch: Keep an eye out for cabbage loopers and aphids. Use row covers early on or handpick pests. BT spray is effective for caterpillers.
Harvesting Your Broccoli
Harvest when the central head is tight, firm, and dark green, before the flower buds start to swell and open. Cut the main stem at a slant about 5-6 inches below the head. After the main head is harvested, many varieties produce smaller side shoots for weeks. Keep picking to encourage more growth.
Recommended Varieties for Our Region
Choosing the right type helps ensure success.
- For Spring: Fast-maturing varieties like ‘Green Goliath’ or ‘Calabrese’.
- For Fall: Try slower-growing, large-headed types like ‘Belstar’ or ‘Arcadia’, which are more heat-tolerant.
- All-Season Standbys: ‘De Cicco’ is a reliable heirloom for side shoots, and ‘Waltham 29’ is very cold-tolerant.
Common Problems and Solutions
Bolting (Flowering Too Early): Caused by stress from heat or inconsistent watering. Stick to the planting windows and water regularly.
Loose, Bitter Heads: Usually a result of too much heat or not enough water during head formation.
Small Heads: Often due to inadequate sunlight (broccoli needs full sun) or poor soil fertility. Don’t skip the compost and fertilizer.
Frequently Asked Questions
Can I grow broccoli in Northern California year-round?
Not quite. While our climate is mild, summer heat and winter frost limit it. The spring and fall windows are your best bet.
What is the latest I can plant broccoli in fall?
You can transplant as late as early September in many coastal and inland areas for a winter harvest, but growth will slow as daylight fades.
How do I protect broccoli from frost?
Young plants can handle a light frost, but a hard freeze can damage them. Use floating row covers or cloches for protection on cold nights.
Why are my broccoli leaves turning yellow?
This could be a sign of nitrogen deficiency, overwatering, or a pest issue like aphids. Check the undersides of leaves and review your feeding schedule.
By aligning your gardening with the natural rhythms of Northern California, you can enjoy fresh, homegrown broccoli for much of the year. Paying attention to your local conditions and these timing guidelines will set you up for a succesful harvest.