When to plant Cosmos in Palm Beach County, FL
Spring Cosmos in Palm Beach County goes in December 30–January 20, once nighttime temps stop dipping near freezing.
When to Plant Cosmos in Palm Beach County, FL
Your June gardening checklist
June is a pivotal month for Palm Beach County, Florida gardens. Focus on these tasks first and you'll set up the rest of the season for success.
-
Basket week: cosmos
Morning harvests are best — cooler temperatures mean crisper produce and longer fridge life.
July 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.
Palm Beach County, Florida is in USDA Zone 10b. The average last spring frost is February 17 and the first fall frost is April 15, giving you a growing season of approximately 57 days.
At an elevation of 355 feet, Palm Beach County receives approximately 50 inches of rainfall annually with predominantly sand soil. Summer highs average 93°F, providing good warmth for Cosmos during the growing season. Sandy soil warms quickly in spring — great for early planting — but Cosmos will need more frequent watering and organic matter to retain nutrients.
Palm Beach County Soil Profile
Soil Type
Sand
Soil pH
5.1-5.9
Drainage
Well Drained
Soil Compatibility in Palm Beach County
How your county's soil matches Cosmos's growing requirements.
Soil pH
Your soil pH (5.1–5.9) is more acidic than Cosmos prefers (6.0–8.0). Add garden lime to raise pH.
Soil Texture
Sandy soil in Palm Beach County warms quickly in spring but drains fast. Cosmos will need more frequent watering and regular compost additions to retain nutrients.
Drainage
Drainage is adequate for Cosmos.
Organic Matter
Organic matter is low (1.3%). Add 2-3 inches of compost before planting Cosmos.
How to Plant Cosmos
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 | — | 2.4" | 0" | ❄️ Dormant |
| Feb | 2.2" | 2.3" | 0" | ✅ Rainfall sufficient |
| Mar | 2.2" | 3.2" | 0" | ✅ Rainfall sufficient |
| Apr | 2.2" | 2.4" | 0" | ✅ Rainfall sufficient |
| May | 2.2" | 3.3" | 0" | ✅ Rainfall sufficient |
| Jun | 2.2" | 6.2" | 0" | ✅ Rainfall sufficient |
| Jul | 2.2" | 7.3" | 0" | ✅ Rainfall sufficient |
| Aug | 2.2" | 7.4" | 0" | ✅ Rainfall sufficient |
| Sep | 2.2" | 7" | 0" | ✅ Rainfall sufficient |
| Oct | 2.2" | 4.2" | 0" | ✅ Rainfall sufficient |
| Nov | — | 2" | 0" | ❄️ Dormant |
| Dec | — | 2.2" | 0" | ❄️ Dormant |
Water needs are for active growing months only (Feb–Oct in Palm Beach 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 — Palm Beach County, FL
Cosmos Planting Calendar
| Activity | When | Date Range |
|---|---|---|
| Start Indoors | January 20 | Jan 20 – Feb 3 |
| Transplant Outdoors | December 30 | Dec 30 – Jan 13 |
| Direct Sow | December 30 | Dec 30 – Jan 20 |
| Bloom | March 10 | Mar 10 – Oct 6 |
Plant 0.3" deep · 12" apart · Rows 18" apart
Month-by-Month Timeline
| Month | Activities |
|---|---|
| January | Start Indoors Transplant Outdoors Direct Sow |
| February | Start Indoors |
| March | Bloom |
| April | Bloom |
| May | Bloom |
| June | Bloom |
| July | Bloom |
| August | Bloom |
| September | Bloom |
| October | Bloom |
| November | — |
| December | Transplant Outdoors Direct Sow |
Growing Conditions
☀️ Sun
Full Sun (6-8+ hours)
💧 Water
0.5"/week · Only during dry spells
📅 Days to Maturity
60–90 days
🧪 Soil pH
Needs 6–8 · Your soil: too_acidic
🗺️ USDA Zone
Zone 10b
📆 Growing Season
57 days in Palm Beach County
Growing Tips for Cosmos in Palm Beach County
Direct sow Cosmos outdoors after February 17 in Palm Beach County when soil has warmed and frost danger has passed.
Sandy soil in Palm Beach County dries quickly — mulch Cosmos with 2-3 inches of straw and water deeply 2-3 times per week rather than lightly every day.
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 Palm Beach County, FL?
Palm Beach County is in Zone 10b with an average last frost of February 17. Plan your Cosmos planting based on this frost date — see the calendar above for exact timing.
What planting zone is Palm Beach County, FL?
Palm Beach County, Florida is in USDA Hardiness Zone 10b. The average last spring frost is February 17 and first fall frost is .
When should I plant Cosmos in Palm Beach County, FL?
In Palm Beach County, FL, plant Cosmos after the last frost (around January 1) and before the first frost (around December 31). Best results when soil holds above 50°F.
What growing zone is Palm Beach County, FL for Cosmos?
Palm Beach County sits in USDA Zone 10b. Cosmos grows reliably in zones 2a through 11b, so it's a good fit here.
Can Cosmos grow in Palm Beach County's climate?
Yes — Cosmos grows well in Palm Beach County's temperate climate. Palm Beach County averages a 365-day frost-free season, with last frost around January 1 and first frost around December 31.
Your Palm Beach County Garden Planner — Free
A 22-page printable planner built for Palm Beach County (Zone 10b). Planting dates, a month-by-month schedule, harvest log, seed inventory, and succession charts — all dialed in for your exact growing season.