When to plant Cosmos in Nassau County, FL
Nassau County's spring Cosmos window runs January 17 through February 7. aim for a steady week of warm soil before planting.
When to Plant Cosmos in Nassau County, FL
July in Nassau County, Florida — your action list
July rewards gardeners who work with the weather, not against it. Here's how to stay in step this month in Nassau County, Florida.
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Basket week: cosmos
Check every 1–2 days. Many of these get tough or go to seed if you wait too long.
August prep starts now
- First harvests: cosmos
Cosmos (Cosmos bipinnatus) is an airy, feathery-foliaged cottage garden annual from Mexico that thrives on neglect. It produces delicate daisy-like blooms in shades of pink, white, and magenta from midsummer until frost. Cosmos is a prolific self-sower — once established in a garden it often returns year after year without replanting. Excellent habitat plant for beneficial insects.
Nassau County, Florida is in USDA Zone 9a. The average last spring frost is February 14 and the first fall frost is December 1, giving you a growing season of approximately 290 days.
At an elevation of 408 feet, Nassau County receives approximately 57.9 inches of rainfall annually with predominantly sand soil. Summer highs average 101°F, so Cosmos may need afternoon shade and extra watering during peak heat. Sandy soil warms quickly in spring — great for early planting — but Cosmos will need more frequent watering and organic matter to retain nutrients. Ample rainfall means less supplemental watering, but ensure good drainage to prevent Cosmos root diseases.
Nassau County Soil Profile
Soil Type
Sand
Soil pH
5.2-5.8
Drainage
Well Drained
Cosmos 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 Nassau County
How your county's soil matches Cosmos's growing requirements.
Soil pH
Your soil pH (5.2–5.8) is more acidic than Cosmos prefers (6.0–8.0). Add garden lime to raise pH.
Soil Texture
Sandy soil in Nassau County warms quickly in spring but drains fast. Cosmos will need more frequent watering and regular compost additions to retain nutrients.
Organic Matter
Organic matter is low (1.4%). Add 2-3 inches of compost before planting Cosmos.
How to Plant Cosmos
Succession Planting Cosmos
Sow every 6.9 weeks. Last sowing by Sep 02 to harvest before frost.
Cosmos Water Budget
Monthly Watering Guide for Cosmos
Cosmos 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 | Cosmos Needs | Rainfall | You Supplement | Action |
|---|---|---|---|---|
| Jan | — | 2.8" | 0" | ❄️ Dormant |
| Feb | 2.2" | 3.2" | 0" | ✅ Rainfall sufficient |
| Mar | 2.2" | 3.7" | 0" | ✅ Rainfall sufficient |
| Apr | 2.2" | 2.9" | 0" | ✅ Rainfall sufficient |
| May | 2.2" | 4.1" | 0" | ✅ Rainfall sufficient |
| Jun | 2.2" | 6.6" | 0" | ✅ Rainfall sufficient |
| Jul | 2.2" | 7.9" | 0" | ✅ Rainfall sufficient |
| Aug | 2.2" | 8.7" | 0" | ✅ Rainfall sufficient |
| Sep | 2.2" | 7.9" | 0" | ✅ Rainfall sufficient |
| Oct | 2.2" | 5.3" | 0" | ✅ Rainfall sufficient |
| Nov | 2.2" | 2.2" | 0" | ✅ Rainfall sufficient |
| Dec | 2.2" | 2.5" | 0" | ✅ Rainfall sufficient |
Water needs are for active growing months only (Feb–Dec in Nassau County). Supplement amounts are based on average rainfall — actual needs vary with temperature, soil, and mulching.
Cosmos 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.
Cosmos Planting Timeline — Nassau County, FL
Cosmos Planting Calendar
| Activity | When | Date Range |
|---|---|---|
| Start Indoors | January 17 | Jan 17 – Jan 31 |
| Transplant Outdoors | January 17 | Jan 17 – Jan 31 |
| Direct Sow | January 17 | Jan 17 – Feb 7 |
| Bloom | March 28 | Mar 28 – Sep 12 |
Plant 0.3" deep · 12" apart · Rows 18" apart
Month-by-Month Timeline
| Month | Activities |
|---|---|
| January | Start Indoors Transplant Outdoors Direct Sow |
| February | Direct Sow |
| March | Bloom |
| 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 · Natural rainfall sufficient
📅 Days to Maturity
60–90 days
🧪 Soil pH
Needs 6–8 · Your soil: too_acidic
🗺️ USDA Zone
Zone 9a
📆 Growing Season
290 days in Nassau County
Growing Tips for Cosmos in Nassau County
Direct sow Cosmos outdoors after February 14 in Nassau County when soil has warmed and frost danger has passed.
Sandy soil in Nassau County dries quickly — mulch Cosmos with 2-3 inches of straw and water deeply 2-3 times per week rather than lightly every day.
With summer highs reaching 101°F in Nassau County, provide afternoon shade for Cosmos and water deeply in the morning.
Common pests for Cosmos in this region include aphids and slugs. Use row covers early in the season and inspect plants weekly.
General growing tips
Direct-sow after last frost; cosmos germinates readily at 65-80°F in 7-10 days. Avoid rich soil — excess fertility produces lush foliage at the expense of blooms. Cosmos tolerates poor, dry soil exceptionally well. Pinch seedlings at 8 inches to encourage branching. Self-sows freely; allow some seed heads to mature and drop for a no-fuss perennial effect in warm climates.
Companion Planting
Good Companions
Check more plant combinations with our Companion Planting Checker →
Cosmos in Other Locations
Frequently Asked Questions
When should I plant Cosmos in Nassau County, FL?
Nassau County is in Zone 9a with an average last frost of February 14. Plan your Cosmos planting based on this frost date — see the calendar above for exact timing.
What planting zone is Nassau County, FL?
Nassau County, Florida is in USDA Hardiness Zone 9a. The average last spring frost is February 14 and first fall frost is December 1.
When should I plant Cosmos in Nassau County, FL?
In Nassau County, FL, plant Cosmos after the last frost (around February 14) and before the first frost (around December 1). Best results when soil holds above 50°F.
What growing zone is Nassau County, FL for Cosmos?
Nassau County sits in USDA Zone 9a. Cosmos grows reliably in zones 2a through 11b, so it's a good fit here.
Can Cosmos grow in Nassau County's climate?
Yes — Cosmos grows well in Nassau County's temperate climate. Nassau County averages a 291-day frost-free season, with last frost around February 14 and first frost around December 1.
Your Nassau County Garden Planner — Free
A 22-page printable planner built for Nassau County (Zone 9a). Planting dates, a month-by-month schedule, harvest log, seed inventory, and succession charts — all dialed in for your exact growing season.