When to Plant Broccoli in Honolulu County, HI
Broccoli is a nutrient-dense cool-season crop that produces large central heads followed by smaller side shoots. It is one of the most popular garden vegetables.
Honolulu County, Hawaii is in USDA Zone 11b. The average last spring frost is January 1 and the first fall frost is December 31, giving you a growing season of approximately 364 days.
At an elevation of 235 feet, Honolulu County receives approximately 44.3 inches of rainfall annually with predominantly silty clay soil. Summer highs average 88°F, providing good warmth for Broccoli during the growing season. Clay soil retains moisture well for Broccoli, but amend with compost to improve drainage and prevent root rot.
Honolulu County Soil Profile
Soil Type
Silty Clay
Soil pH
5.7-6.4
Drainage
Well Drained
Plant Planting Risk Windows
Percentages indicate frost risk at transplant. The 70% safe window means there is a 30% chance of frost after transplant — suitable for cold-hardy crops or gardeners with frost protection. The 90% safe window is best for tender plants.
Soil Compatibility in Honolulu County
How your county's soil matches Broccoli's growing requirements.
Soil pH
Your soil pH (5.7–6.4) overlaps with Broccoli's range (6.0–7.0), though not a perfect match.
Soil Texture
Your silty clay soil in Honolulu County is workable for Broccoli. Add compost annually to improve structure.
Organic Matter
Organic matter is moderate (3.6%). Annual compost additions will help Broccoli.
How to Plant Broccoli
Fall planting: Sow 8 weeks before your first frost date for a fall harvest.
How Much Broccoli to Grow
For a family of 4, plant approximately 12 broccoli plants in about 30 sq ft. In Honolulu County's 364-day season, you'll have plenty of time for a full harvest. Plan your garden layout →
Plant Water Budget
Water stress score is 6/10 — consider drought-tolerant varieties and mulching
Monthly Watering Guide for Broccoli
Broccoli needs approximately 1 inches of water per week (4.3" per month). Here's how your county's rainfall compares month by month.
| Month | Broccoli Needs | Rainfall | You Supplement | Action |
|---|---|---|---|---|
| Jan | 4.3" | 6.4" | 0" | ✅ Rainfall sufficient |
| Feb | 4.3" | 4.7" | 0" | ✅ Rainfall sufficient |
| Mar | 4.3" | 6.2" | 0" | ✅ Rainfall sufficient |
| Apr | 4.3" | 3.9" | 0.4" | 💧 Light watering |
| May | 4.3" | 2.5" | 1.8" | 💧 Light watering |
| Jun | 4.3" | 1.3" | 3" | 🚿 Regular watering |
| Jul | 4.3" | 0.9" | 3.4" | 🚿 Regular watering |
| Aug | 4.3" | 1.3" | 3" | 🚿 Regular watering |
| Sep | 4.3" | 2.2" | 2.1" | 💧 Light watering |
| Oct | 4.3" | 4.4" | 0" | ✅ Rainfall sufficient |
| Nov | 4.3" | 4.2" | 0.1" | 💧 Light watering |
| Dec | 4.3" | 6.2" | 0" | ✅ Rainfall sufficient |
Water needs are for active growing months only (Jan–Dec in Honolulu County). Supplement amounts are based on average rainfall — actual needs vary with temperature, soil, and mulching.
Broccoli Heat Requirements (GDD)
What are Growing Degree Days (GDD)?
Growing Degree Days measure the total warmth your plants receive during the growing season. Think of it as a "heat bank" — every day above 50°F deposits warmth that helps your plants grow.
Each plant needs a certain amount of accumulated heat to mature. If your county provides more GDD than the plant needs, it's a great fit. If it's close, you may want to choose faster-maturing varieties or start seeds indoors to get a head start.
Broccoli Planting Timeline — Honolulu County, HI
Broccoli Planting Calendar
| Activity | When | Date Range |
|---|---|---|
| Start Indoors | December 4 | Dec 4 – Dec 18 |
| Transplant Outdoors | January 1 | Jan 1 – Jan 15 |
| Direct Sow | December 11 | Dec 11 – Jan 1 |
| Harvest | March 5 | Mar 5 – Apr 16 |
| Fall Sowing | November 5 | Nov 5 – Nov 19 |
Plant 1" deep · 15" apart · Rows 24" apart
Month-by-Month Timeline
| Month | Activities |
|---|---|
| January | Transplant Outdoors Direct Sow |
| February | — |
| March | Harvest |
| April | Harvest |
| May | — |
| June | — |
| July | — |
| August | — |
| September | — |
| October | — |
| November | Fall Sowing |
| December | Start Indoors Direct Sow |
Growing Conditions
☀️ Sun
Full Sun (6-8+ hours)
💧 Water
1"/week · 1-2 times/week
📅 Days to Maturity
60–90 days
🧪 Soil pH
Needs 6–7 · Your soil: acceptable
🗺️ USDA Zone
Zone 11b
📆 Growing Season
364 days in Honolulu County
Growing Tips for Broccoli in Honolulu County
With Honolulu County's clay soil (36% clay), work in 3-4 inches of compost before planting Broccoli. Avoid tilling when soil is wet to prevent compaction.
Common pests for Broccoli in this region include cabbage worm and flea beetles. Use row covers early in the season and inspect plants weekly.
General growing tips
Start seeds indoors 6-8 weeks before last frost. Provide consistent moisture to prevent hollow stems. Harvest heads before yellow flowers appear.
Companion Planting
Good Companions
Avoid Planting Near
Check more plant combinations with our Companion Planting Checker →
Isolate 1/2 mile from other brassicas. Biennial — must overwinter roots.
Broccoli in Other Locations
Frequently Asked Questions
When should I plant Broccoli in Honolulu County, HI?
Honolulu County is in Zone 11b with an average last frost of January 1. Plan your Broccoli planting based on this frost date — see the calendar above for exact timing.
What planting zone is Honolulu County, HI?
Honolulu County, Hawaii is in USDA Hardiness Zone 11b. The average last spring frost is January 1 and first fall frost is December 31.
Plan Your Garden with Confidence
Get our free Garden Planner — designed to help Honolulu County gardeners in Zone 11b organize planting dates, track what's growing, and never miss a planting window.
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