When to plant Coreopsis in Pima County, AZ
For Coreopsis in Pima County, the safe spring window opens around March 11 and closes around April 1. Last expected frost is April 1, first fall frost November 9, giving a 222-day growing season.
When to Plant Coreopsis in Pima County, AZ
Your July game plan for Pima County, Arizona
Welcome to July in Zone 9b. These are the moves that will have the biggest impact on your growing season.
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Bring in the coreopsis
If you can't use it all right away, check the food-preservation section of your planner.
Before August arrives, get these ready
- First harvests: coreopsis
Coreopsis (Tickseed) is a cheerful, long-blooming native perennial that produces a continuous flush of bright yellow, gold, or bi-colored daisy-like flowers from early summer well into fall. One of the most reliable cut-and-come-again bloomers in the perennial garden, it thrives in hot, dry, sunny conditions and poor soil where many competitors struggle. An invaluable nectar source for native bees and butterflies, and a butterfly host plant for several species.
Pima County, Arizona is in USDA Zone 9b. The average last spring frost is April 1 and the first fall frost is November 9, giving you a growing season of approximately 222 days.
At an elevation of 4,327 feet, Pima County receives approximately 14.4 inches of rainfall annually with predominantly sandy loam soil. Summer highs average 103°F, so Coreopsis may need afternoon shade and extra watering during peak heat. Sandy soil warms quickly in spring — great for early planting — but Coreopsis will need more frequent watering and organic matter to retain nutrients. With low rainfall, drip irrigation is essential for growing Coreopsis successfully. Mulch heavily to conserve soil moisture.
Pima County Soil Profile
Soil Type
Sandy Loam
Soil pH
6.8-8.3
Drainage
Well Drained
Coreopsis 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 Pima County
How your county's soil matches Coreopsis's growing requirements.
Soil pH
Your soil pH (6.8–8.3) is more alkaline than Coreopsis prefers (5.5–7.5). Add sulfur or peat moss to lower pH.
Soil Texture
Sandy soil in Pima County warms quickly in spring but drains fast. Coreopsis will need more frequent watering and regular compost additions to retain nutrients.
Drainage
Drainage is adequate for Coreopsis.
Organic Matter
Organic matter is low (0.9%). Add 2-3 inches of compost before planting Coreopsis.
How to Plant Coreopsis
Succession Planting Coreopsis
Sow every 6.9 weeks. Last sowing by Aug 21 to harvest before frost.
Coreopsis Water Budget
Water stress score is 10/10 — consider drought-tolerant varieties and mulching
Monthly Watering Guide for Coreopsis
Coreopsis 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 | Coreopsis Needs | Rainfall | You Supplement | Action |
|---|---|---|---|---|
| Jan | — | 0.9" | 0" | ❄️ Dormant |
| Feb | — | 0.8" | 0" | ❄️ Dormant |
| Mar | — | 0.7" | 0" | ❄️ Dormant |
| Apr | 2.2" | 0.5" | 1.7" | 🚿 Regular watering |
| May | 2.2" | 0.4" | 1.8" | 🚿 Regular watering |
| Jun | 2.2" | 0.5" | 1.7" | 🚿 Regular watering |
| Jul | 2.2" | 2.7" | 0" | ✅ Rainfall sufficient |
| Aug | 2.2" | 3.2" | 0" | ✅ Rainfall sufficient |
| Sep | 2.2" | 1.9" | 0.3" | 💧 Light watering |
| Oct | 2.2" | 1.4" | 0.8" | 💧 Light watering |
| Nov | 2.2" | 0.7" | 1.5" | 🚿 Regular watering |
| Dec | — | 0.9" | 0" | ❄️ Dormant |
Water needs are for active growing months only (Apr–Nov in Pima County). Supplement amounts are based on average rainfall — actual needs vary with temperature, soil, and mulching.
Coreopsis 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.
Coreopsis Planting Timeline — Pima County, AZ
Coreopsis Planting Calendar
| Activity | When | Date Range |
|---|---|---|
| Start Indoors | February 4 | Feb 4 – Feb 18 |
| Transplant Outdoors | March 18 | Mar 18 – Apr 1 |
| Direct Sow | March 11 | Mar 11 – Apr 1 |
| Bloom | May 13 | May 13 – Oct 14 |
Plant 0.1" deep · 18" apart · Rows 24" apart
Month-by-Month Timeline
| Month | Activities |
|---|---|
| January | — |
| February | Start Indoors |
| March | Transplant Outdoors Direct Sow |
| April | Transplant Outdoors Direct Sow |
| May | Bloom |
| June | Bloom |
| July | Bloom |
| August | Bloom |
| September | Bloom |
| October | Bloom |
| November | — |
| December | — |
Growing Conditions
☀️ Sun
Full Sun (6-8+ hours)
💧 Water
0.5"/week · 1-2 times/week
📅 Days to Maturity
60–80 days
🧪 Soil pH
Needs 5.5–7.5 · Your soil: too_alkaline
🗺️ USDA Zone
Zone 9b
📆 Growing Season
222 days in Pima County
Growing Tips for Coreopsis in Pima County
Direct sow Coreopsis outdoors after April 01 in Pima County when soil has warmed and frost danger has passed.
Sandy soil in Pima County dries quickly — mulch Coreopsis with 2-3 inches of straw and water deeply 2-3 times per week rather than lightly every day.
With summer highs reaching 103°F in Pima County, provide afternoon shade for Coreopsis and water deeply in the morning.
Common pests for Coreopsis in this region include aphids and slugs. Use row covers early in the season and inspect plants weekly.
Pima County receives only 14" of rain annually. Coreopsis 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. Seeds germinate easily without stratification. Thrives in poor to average, well-drained soil — rich soil promotes foliage over flowers. Drought tolerant once established; overwatering is the most common mistake. Deadhead spent blooms to maintain continuous flowering through the season. Shear plants by one-third in midsummer for a fresh flush of late-season blooms. Year 2+ plants bloom most heavily. Divide every 2–3 years in early spring to rejuvenate crowded clumps.
Companion Planting
Good Companions
Check more plant combinations with our Companion Planting Checker →
Coreopsis in Other Locations
Frequently Asked Questions
When should I plant Coreopsis in Pima County, AZ?
Pima County is in Zone 9b with an average last frost of April 1. Plan your Coreopsis planting based on this frost date — see the calendar above for exact timing.
What planting zone is Pima County, AZ?
Pima County, Arizona is in USDA Hardiness Zone 9b. The average last spring frost is April 1 and first fall frost is November 9.
When should I plant Coreopsis in Pima County, AZ?
In Pima County, AZ, plant Coreopsis after the last frost (around April 1) and before the first frost (around November 9). Best results when soil holds above 50°F.
What growing zone is Pima County, AZ for Coreopsis?
Pima County sits in USDA Zone 9b. Coreopsis grows reliably in zones 3a through 9b, so it's a good fit here.
Can Coreopsis grow in Pima County's climate?
Yes — Coreopsis grows well in Pima County's temperate climate. Pima County averages a 222-day frost-free season, with last frost around April 1 and first frost around November 9.
Your Pima County Garden Planner — Free
A 22-page printable planner built for Pima 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.