When to Plant Cosmos in Rich County, UT
Rich County, Utah gardeners: here's your June plan
We've pulled the most time-sensitive tasks for Rich County, Utah this June and put them front and centre. Tackle them in order.
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Move cosmos from tray to bed
Your last frost (May 31) has passed. These warm-season crops can handle outdoor soil now.
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Put cosmos seeds straight in the ground
Mark the row. Birds and stray feet both have opinions about unmarked beds.
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Get cosmos seeds going inside
Label every cell. You will absolutely forget which is which otherwise.
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.
Rich County, Utah is in USDA Zone 5a. The average last spring frost is May 31 and the first fall frost is September 15, giving you a growing season of approximately 107 days.
At an elevation of 5,803 feet, Rich County receives approximately 18 inches of rainfall annually with predominantly loam soil. Summer highs average 81°F, so choose short-season varieties of Cosmos to ensure they mature before fall. With low rainfall, drip irrigation is essential for growing Cosmos successfully. Mulch heavily to conserve soil moisture.
Rich County Soil Profile
Soil Type
Loam
Soil pH
6.5-8.2
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 Rich County
How your county's soil matches Cosmos's growing requirements.
Soil pH
Your soil pH (6.5–8.2) overlaps with Cosmos's range (6.0–8.0), though not a perfect match.
Soil Texture
The loam soil in Rich County is excellent for Cosmos — good drainage, moisture retention, and nutrient holding capacity.
Organic Matter
Organic matter is moderate (2.1%). Annual compost additions will help Cosmos.
How to Plant Cosmos
Cosmos Water Budget
Water stress score is 10/10 — consider drought-tolerant varieties and mulching
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 | — | 1.3" | 0" | ❄️ Dormant |
| Feb | — | 1.1" | 0" | ❄️ Dormant |
| Mar | — | 1.7" | 0" | ❄️ Dormant |
| Apr | — | 2" | 0" | ❄️ Dormant |
| May | 2.2" | 1.9" | 0.3" | 💧 Light watering |
| Jun | 2.2" | 1.4" | 0.8" | 💧 Light watering |
| Jul | 2.2" | 1.7" | 0.5" | 💧 Light watering |
| Aug | 2.2" | 1.7" | 0.5" | 💧 Light watering |
| Sep | 2.2" | 1.4" | 0.8" | 💧 Light watering |
| Oct | — | 1.6" | 0" | ❄️ Dormant |
| Nov | — | 1.1" | 0" | ❄️ Dormant |
| Dec | — | 1.1" | 0" | ❄️ Dormant |
Water needs are for active growing months only (May–Sep in Rich 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 — Rich County, UT
Cosmos Planting Calendar
| Activity | When | Date Range |
|---|---|---|
| Start Indoors | May 3 | May 3 – May 17 |
| Transplant Outdoors | June 7 | Jun 7 – Jun 21 |
| Direct Sow | June 7 | Jun 7 – Jun 28 |
| Bloom | August 16 | Aug 16 – Nov 8 |
Plant 0.3" deep · 12" apart · Rows 18" apart
Month-by-Month Timeline
| Month | Activities |
|---|---|
| January | — |
| February | — |
| March | — |
| April | — |
| May | Start Indoors |
| June | Transplant Outdoors Direct Sow |
| July | — |
| August | Bloom |
| September | Bloom |
| October | Bloom |
| November | Bloom |
| 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: acceptable
🗺️ USDA Zone
Zone 5a
📆 Growing Season
107 days in Rich County
Growing Tips for Cosmos in Rich County
Direct sow Cosmos outdoors after May 31 in Rich County when soil has warmed and frost danger has passed.
Common pests for Cosmos in this region include aphids and slugs. Use row covers early in the season and inspect plants weekly.
Rich County receives only 18" of rain annually. Cosmos needs consistent moisture — install drip irrigation or water deeply 2-3 times per week.
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 Rich County, UT?
Rich County is in Zone 5a with an average last frost of May 31. Plan your Cosmos planting based on this frost date — see the calendar above for exact timing.
What planting zone is Rich County, UT?
Rich County, Utah is in USDA Hardiness Zone 5a. The average last spring frost is May 31 and first fall frost is September 15.
Your Rich County Garden Planner — Free
A 22-page printable planner built for Rich County (Zone 5a). Planting dates, a month-by-month schedule, harvest log, seed inventory, and succession charts — all dialed in for your exact growing season.