When to plant Black-eyed Susan in Contra Costa County County,
For Black-eyed Susan in Contra Costa County County, the safe spring window opens around February 5 and closes around February 26. Last expected frost is February 26, first fall frost November 29, giving a 277-day growing season.
When to Plant Black-eyed Susan in Contra Costa County, CA
What to do in June
Welcome to June in Zone 9b. These are the moves that will have the biggest impact on your growing season.
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Start harvesting black-eyed susan
The more you pick, the more the plant produces. Letting fruit overripen tells the plant it's time to stop.
Looking ahead to July
- First harvests: black-eyed susan
Rudbeckia hirta (Black-eyed Susan) is one of the most recognizable and adaptable native wildflowers in North America. Its bright golden-yellow daisy petals radiate from a dark brown central cone, providing months of color from midsummer into fall. Technically a short-lived perennial that self-seeds freely — colonies persist indefinitely in the garden — it thrives in poor soils, tolerates drought, and is irresistible to bees, butterflies, and goldfinches.
Contra Costa County, California is in USDA Zone 9b. The average last spring frost is February 26 and the first fall frost is November 29, giving you a growing season of approximately 276 days.
At an elevation of 88 feet, Contra Costa County receives approximately 19 inches of rainfall annually with predominantly loam soil. Summer highs average 93°F, providing good warmth for Black-eyed Susan during the growing season. With low rainfall, drip irrigation is essential for growing Black-eyed Susan successfully. Mulch heavily to conserve soil moisture.
Contra Costa County Soil Profile
Soil Type
Loam
Soil pH
6.7-7.8
Drainage
Well Drained
Black-eyed Susan 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 Contra Costa County
How your county's soil matches Black-eyed Susan's growing requirements.
Soil pH
Your soil pH (6.7–7.8) is more alkaline than Black-eyed Susan prefers (6.0–7.0). Add sulfur or peat moss to lower pH.
Soil Texture
The loam soil in Contra Costa County is excellent for Black-eyed Susan — good drainage, moisture retention, and nutrient holding capacity.
Organic Matter
Organic matter is moderate (3.0%). Annual compost additions will help Black-eyed Susan.
How to Plant Black-eyed Susan
Succession Planting Black-eyed Susan
Sow every 6.9 weeks. Last sowing by Sep 10 to harvest before frost.
Black-eyed Susan Water Budget
Water stress score is 8/10 — consider drought-tolerant varieties and mulching
Monthly Watering Guide for Black-eyed Susan
Black-eyed Susan needs approximately 0.5 inches of water per week (2.2" per month). Here's how your county's rainfall compares month by month.
| Month | Black-eyed Susan Needs | Rainfall | You Supplement | Action |
|---|---|---|---|---|
| Jan | — | 4.1" | 0" | ❄️ Dormant |
| Feb | 2.2" | 4.5" | 0" | ✅ Rainfall sufficient |
| Mar | 2.2" | 3" | 0" | ✅ Rainfall sufficient |
| Apr | 2.2" | 1.5" | 0.7" | 💧 Light watering |
| May | 2.2" | 0.6" | 1.6" | 🚿 Regular watering |
| Jun | 2.2" | 0.1" | 2.1" | 🚿 Regular watering |
| Jul | 2.2" | 0" | 2.2" | 🚿 Regular watering |
| Aug | 2.2" | 0" | 2.2" | 🚿 Regular watering |
| Sep | 2.2" | 0.2" | 2" | 🚿 Regular watering |
| Oct | 2.2" | 0.7" | 1.5" | 🚿 Regular watering |
| Nov | 2.2" | 1.6" | 0.6" | 💧 Light watering |
| Dec | — | 2.7" | 0" | ❄️ Dormant |
Water needs are for active growing months only (Feb–Nov in Contra Costa County). Supplement amounts are based on average rainfall — actual needs vary with temperature, soil, and mulching.
Black-eyed Susan 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.
Black-eyed Susan Planting Timeline — Contra Costa County, CA
Black-eyed Susan Planting Calendar
| Activity | When | Date Range |
|---|---|---|
| Start Indoors | January 1 | Jan 1 – Jan 15 |
| Transplant Outdoors | February 12 | Feb 12 – Feb 26 |
| Direct Sow | February 5 | Feb 5 – Feb 26 |
| Bloom | April 23 | Apr 23 – Sep 10 |
· 18" apart · Rows 24" apart
Month-by-Month Timeline
| Month | Activities |
|---|---|
| January | Start Indoors |
| February | Transplant Outdoors Direct Sow |
| March | — |
| April | Bloom |
| May | Bloom |
| June | Bloom |
| July | Bloom |
| August | Bloom |
| September | Bloom |
| October | — |
| November | — |
| December | — |
Growing Conditions
☀️ Sun
Full Sun (6-8+ hours)
💧 Water
0.5"/week · Only during dry spells
📅 Days to Maturity
60–80 days
🧪 Soil pH
Needs 6–7 · Your soil: too_alkaline
🗺️ USDA Zone
Zone 9b
📆 Growing Season
276 days in Contra Costa County
Growing Tips for Black-eyed Susan in Contra Costa County
Direct sow Black-eyed Susan outdoors after February 26 in Contra Costa County when soil has warmed and frost danger has passed.
Common pests for Black-eyed Susan in this region include aphids and slugs. Use row covers early in the season and inspect plants weekly.
Contra Costa County receives only 19" of rain annually. Black-eyed Susan needs consistent moisture — install drip irrigation or water deeply 2-3 times per week.
General growing tips
Start seeds indoors 8–10 weeks before last frost or direct-sow after last frost (needs light to germinate — press seeds onto soil surface, do not cover). Thrives in average to poor soil; rich soil causes floppy stems. Deadhead for extended bloom but leave some seed heads for winter wildlife interest and self-seeding. Although technically short-lived (3–5 years), prolific self-seeding maintains the colony. Year 2+ plants bloom most heavily. Divide every 3 years to maintain vigor.
Companion Planting
Good Companions
Check more plant combinations with our Companion Planting Checker →
Black-eyed Susan in Other Locations
Frequently Asked Questions
When should I plant Black-eyed Susan in Contra Costa County, CA?
Contra Costa County is in Zone 9b with an average last frost of February 26. Plan your Black-eyed Susan planting based on this frost date — see the calendar above for exact timing.
What planting zone is Contra Costa County, CA?
Contra Costa County, California is in USDA Hardiness Zone 9b. The average last spring frost is February 26 and first fall frost is November 29.
When should I plant Black-eyed Susan in Contra Costa County County, ?
In Contra Costa County County, , plant Black-eyed Susan after the last frost (around February 26) and before the first frost (around November 29). Best results when soil holds above 50°F.
What growing zone is Contra Costa County County, for Black-eyed Susan?
Contra Costa County County sits in USDA Zone 9b. Black-eyed Susan grows reliably in zones 3a through 9b, so it's a good fit here.
Can Black-eyed Susan grow in Contra Costa County County's climate?
Yes — Black-eyed Susan grows well in Contra Costa County County's temperate climate. Contra Costa County County averages a 277-day frost-free season, with last frost around February 26 and first frost around November 29.
Your Contra Costa County Garden Planner — Free
A 22-page printable planner built for Contra Costa County (Zone 9b). Planting dates, a month-by-month schedule, harvest log, seed inventory, and succession charts — all dialed in for your exact growing season.