When to plant Mint in Saint Augustine,
In Saint Augustine, Mint is a single-season spring crop — there's no second fall window. Plant April 24–May 8 for an 90-day harvest, finishing well before the October 15 first frost.
When to Plant Mint in Saint Augustine, IL
Your June gardening checklist
June is a pivotal month for Saint Augustine, IL gardens. Focus on these tasks first and you'll set up the rest of the season for success.
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Pick mint
The more you pick, the more the plant produces. Letting fruit overripen tells the plant it's time to stop.
A few tasks this June that'll pay off in July
- First harvests: mint
Mint is a vigorous perennial herb with refreshing, aromatic leaves used in teas, cocktails, and cooking. It spreads aggressively by underground runners.
Saint Augustine, Illinois is in USDA Zone 5b. The average last spring frost is April 17 and the first fall frost is October 15, giving you a growing season of approximately 181 days.
At an elevation of 1,301 feet, Knox County receives approximately 33.2 inches of rainfall annually with predominantly silt loam soil. Summer highs average 84°F, so choose short-season varieties of Mint to ensure they mature before fall.
Saint Augustine Soil Profile
Soil Type
Silt Loam
Soil pH
6-6.8
Drainage
Well Drained
Mint 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 Saint Augustine
How your county's soil matches Mint's growing requirements.
Soil pH
Your soil pH (6.0–6.8) is within Mint's preferred range (6.0–7.0).
Soil Texture
The silt loam soil in Knox County is excellent for Mint — good drainage, moisture retention, and nutrient holding capacity.
Organic Matter
Organic matter is excellent (4.5%) — Mint will thrive.
How to Plant Mint
Succession Planting Mint
Sow every 6.9 weeks. Last sowing by Jul 17 to harvest before frost.
Mint Water Budget
Water stress score is 6/10 — consider drought-tolerant varieties and mulching
Monthly Watering Guide for Mint
Mint needs approximately 0.7 inches of water per week (3" per month). Here's how your county's rainfall compares month by month.
| Month | Mint Needs | Rainfall | You Supplement | Action |
|---|---|---|---|---|
| Jan | — | 1.3" | 0" | ❄️ Dormant |
| Feb | — | 1.5" | 0" | ❄️ Dormant |
| Mar | — | 2.4" | 0" | ❄️ Dormant |
| Apr | 3" | 3.4" | 0" | ✅ Rainfall sufficient |
| May | 3" | 3.9" | 0" | ✅ Rainfall sufficient |
| Jun | 3" | 3.6" | 0" | ✅ Rainfall sufficient |
| Jul | 3" | 4.1" | 0" | ✅ Rainfall sufficient |
| Aug | 3" | 3.5" | 0" | ✅ Rainfall sufficient |
| Sep | 3" | 2.6" | 0.4" | 💧 Light watering |
| Oct | 3" | 2.7" | 0.3" | 💧 Light watering |
| Nov | — | 2.5" | 0" | ❄️ Dormant |
| Dec | — | 1.6" | 0" | ❄️ Dormant |
Water needs are for active growing months only (Apr–Oct in Knox County). Supplement amounts are based on average rainfall — actual needs vary with temperature, soil, and mulching.
Mint 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.
Mint Planting Timeline — Saint Augustine, IL
Mint Planting Calendar
| Activity | When | Date Range |
|---|---|---|
| Transplant Outdoors | April 24 | Apr 24 – May 8 |
| Harvest | June 26 | Jun 26 – Sep 4 |
Plant 0.5" deep · 8" apart · Rows 12" apart
Month-by-Month Timeline
| Month | Activities |
|---|---|
| January | — |
| February | — |
| March | — |
| April | Transplant Outdoors |
| May | Transplant Outdoors |
| June | Harvest |
| July | Harvest |
| August | Harvest |
| September | Harvest |
| October | — |
| November | — |
| December | — |
Growing Conditions
☀️ Sun
Partial Shade (3-6 hours)
💧 Water
0.7"/week · Natural rainfall sufficient
📅 Days to Maturity
60–90 days
🧪 Soil pH
Needs 6–7 · Your soil: ideal
🗺️ USDA Zone
Zone 5b
📆 Growing Season
181 days in Knox County
Growing Tips for Mint in Saint Augustine
Direct sow Mint outdoors after April 17 in Knox County when soil has warmed and frost danger has passed.
General growing tips
Always grow mint in containers or with underground barriers to control spreading. Harvest regularly to keep plants compact. Cut plants back in late summer for a fresh fall flush.
Companion Planting
Good Companions
Avoid Planting Near
Check more plant combinations with our Companion Planting Checker →
Mint in Other Locations
When should I plant Mint in Saint Augustine, ?
In Saint Augustine, , plant Mint after the last frost (around April 17) and before the first frost (around October 15). Best results when soil holds above 50°F.
What growing zone is Saint Augustine, for Mint?
Saint Augustine sits in USDA Zone 5b. Mint grows reliably in zones 3a through 10b, so it's a good fit here.
Can Mint grow in Saint Augustine's climate?
Yes — Mint grows well in Saint Augustine's temperate climate. Saint Augustine averages a 181-day frost-free season, with last frost around April 17 and first frost around October 15.
Your Knox County Garden Planner — Free
A 22-page printable planner built for Knox County (Zone 5b). Planting dates, a month-by-month schedule, harvest log, seed inventory, and succession charts — all dialed in for your exact growing season.