Audubon County, IA — Planting Guide
Audubon County is in USDA Zone 5a. The average last spring frost is April 28 and the first fall frost is October 3, giving you a growing season of approximately 158 days.
At an elevation of 1,056 ft, Audubon County receives approximately 32.5 in of rainfall annually. Summer highs average 86°F with winter lows around 12°F. The predominant soil type is Silt Loam.
Based on 31 years of NOAA climate station data, the last frost date here varies by 26 days year to year — ranging from April 18 in warm years to May 14 in cold years. The growing season is trending shorter by about 0.51 days per decade. Audubon County scores 71/100 (Good) on the Microclimate Index.
🌡️ Zone
5a (-20°F to -15°F min)
❄️ Last Frost
April 28
🍂 First Frost
October 3
📅 Growing Season
158 days
⛰️ Elevation
1,056 ft
🌧️ Annual Rainfall
32.5 in
Monthly Watering Calendar for Audubon County
When you'll need to water your garden — based on average monthly rainfall vs. the ~1 inch/week most gardens need.
What this means for you: The 1-inch-per-week rule applies to most vegetable crops. Audubon County averages 33" a year — divide by 52 and compare to that 1" target. Some months are above, some below; that's where the calendar earns its keep.
View detailed monthly data
| Month | Avg Rainfall | Rainy Days | Extra Water Needed | Watering Effort |
|---|---|---|---|---|
| Jan | 1.3 in | 7 days | — | None |
| Feb | 1.3 in | 7 days | — | None |
| Mar | 2.1 in | 9 days | — | None |
| Apr | 3.2 in | 9 days | 1.1 in | Moderate |
| May | 4.4 in | 11 days | — | Low |
| Jun | 3.7 in | 10 days | 0.6 in | Moderate |
| Jul | 3.9 in | 9 days | 0.4 in | Low |
| Aug | 3.5 in | 9 days | 0.8 in | Moderate |
| Sep | 2.6 in | 8 days | 1.7 in | High |
| Oct | 2.6 in | 9 days | 1.7 in | High |
| Nov | 2 in | 8 days | — | None |
| Dec | 1.8 in | 7 days | — | None |
Annual total: 32.4 in. Water needs vary by crop — tomatoes need ~1.2"/week while herbs like rosemary need only 0.3"/week. Check individual plant pages for crop-specific water budgets that factor in your county's rainfall and soil drainage.
Audubon County Soil Profile
Soil Type
Silt Loam
Soil pH
5.8-6.8
Drainage
Well Drained
Frost Risk Probability
Based on 31 years of NOAA weather station data from 3 stations
Beginners: Plant frost-sensitive crops (tomatoes, peppers, squash) after the "Safe" date on the left. Harvest or cover them before the "Protect by" date on the right. Hardy crops (lettuce, peas, kale) can go in the yellow transition zones.
How to read this table: "Conservative" means you're safe from frost 9 out of 10 years — best for beginners and frost-sensitive crops. "Average year" is the typical date. "Aggressive" means only 1 in 10 years is that warm — experienced gardeners with frost protection can try these dates.
| Planting Strategy | Last Spring Frost | First Fall Frost | Frost-Free Days |
|---|---|---|---|
| Conservative (safest) | May 14 | Oct 15 | 154 days |
| Cautious | May 5 | Oct 11 | 159 days |
| Average year | Apr 28 | Oct 3 | 158 days |
| Optimistic | Apr 23 | Sep 25 | 155 days |
| Aggressive (risky) | Apr 18 | Sep 19 | 154 days |
Not very — frost dates can vary by ±26 days year-to-year. Use the "Conservative" row in the table below, and keep row covers handy for surprise late frosts.
Slightly — seasons are trending a bit shorter (0.5 days/decade). Stay conservative with planting dates.
Gardening Difficulty Score
Audubon County offers good growing conditions. A little planning around frost dates goes a long way.
Local Gardening Help in Audubon County
Free expert help is closer than you think. Your county's cooperative extension office connects you with trained gardeners, soil testing labs, and local programs — all specific to Audubon County's climate and soil.
County Extension Office
Audubon County Iowa State University Extension Extension Office
Phone: 515-294-6675
Visit Extension Office Website →
Extension offices are run by land-grant universities and funded by the USDA. Their advice is free, research-based, and tailored to your county's specific conditions.
Master Gardener Program
Free gardening help from trained volunteers
Master Gardeners are community volunteers who complete 40–60 hours of university horticultural training. They answer gardening questions, diagnose plant problems, and offer workshops — all free.
Many extension offices run a Master Gardener hotline where you can call or email with photos of plant problems for free diagnosis.
Soil Testing
Available through your extension office
Before amending your soil, get it tested. Your extension office offers soil testing (typically $10–$25) that tells you exact pH, nutrient levels, and amendment recommendations specific to what you want to grow.
Services Available in Audubon County
Finding local nurseries & garden centers in Audubon County
Why Buy Local
Local nurseries carry plants that are proven to grow in your area. Staff can give you advice specific to Audubon County's soil and climate that big-box stores can't. Plants from local growers are typically hardier because they're already acclimated to your zone.
How to Find Them
Search for "nurseries near Audubon County IA" or "garden center Audubon County" on Google Maps. Also check with your extension office — they often maintain lists of reputable local nurseries and plant sales.
Community gardens & gardening groups
Community gardens are a great way to learn from experienced gardeners in your area, especially if you're limited on space. Search "community garden Audubon County IA" or check your extension office and local parks department. Facebook groups like "Audubon County Gardeners" or "Iowa Gardening" are also excellent for local advice and plant swaps.
What to Plant After Your Harvest
After your first crops finish, use the remaining frost-free days to grow a second round.
Show 6 more succession options
Sunlight & Day Length in Audubon County
Monthly daylight hours and peak sun — critical for onion varieties, photoperiod-sensitive plants, and solar garden planning.
Quick context: A 14-hour day in June produces dramatically more photosynthesis than a 10-hour day in November. Audubon County's seasonal swing determines which crops can pack growth into spring vs. limp through fall.
Longest Day
15 hours
Summer solstice daylight
Shortest Day
9 hours
Winter solstice daylight
Peak Sun Hours
9.6 hr/day peak (summer)
Peak sun hours (green dashed line below) account for cloud cover — this is the usable direct sunlight your garden actually receives. Most vegetables need 6+ peak sun hours.
Onion tip: Your long summer days (14+ hours) support long-day onion varieties like Walla Walla, Sweet Spanish, and Ailsa Craig.
View detailed monthly data
| Month | Daylight Hours | Peak Sun Hours | Day Length |
|---|---|---|---|
| January | 9.3 hr | 3.6 hr | Short day |
| February | 10.4 hr | 4.5 hr | Short day |
| March | 11.7 hr | 5.4 hr | Short day |
| April | 13.1 hr | 7 hr | Neutral |
| May | 14.4 hr | 8 hr | Long day |
| June | 15 hr | 9.6 hr | Long day |
| July | 14.7 hr | 9.5 hr | Long day |
| August | 13.7 hr | 8.3 hr | Neutral |
| September | 12.3 hr | 7.4 hr | Neutral |
| October | 10.8 hr | 5.8 hr | Short day |
| November | 9.6 hr | 3.7 hr | Short day |
| December | 9 hr | 3.5 hr | Short day |
Peak sun hours factor in typical cloud cover — use these for solar panel and shade-planning calculations.
Soil Temperature & Composting in Audubon County
Monthly soil temps tell you when to plant warm-season crops, and when your compost pile is actively working.
The practical takeaway: Lettuce germinates at 35°F. Beans want 60°F. Tomatoes 65°F+. Soil temp, not air temp, is what plants feel. Audubon County's monthly curve tells you when each crop actually has the conditions to take off.
Plant Warm Crops When
Soil reaches 60°F+
Soil warm enough from Jun through Sep.
Best Month to Compost
Jun
Microbial activity peaks when soil is warm.
Active Composting
6 months
Solid season. Piles go dormant in winter.
View detailed monthly data
| Month | Soil 4" Deep | Soil 8" Deep | Compost Activity | Time to Finish |
|---|---|---|---|---|
| Jan | 22°F | 30°F | ❄️ Dormant | ~36 weeks |
| Feb | 22°F | 31°F | ❄️ Dormant | ~36 weeks |
| Mar | 30°F | 36°F | ❄️ Dormant | ~36 weeks |
| Apr | 45°F | 43°F | 🐢 Slow | ~24 weeks |
| May | 60°F | 55°F | ♻️ Active | ~14 weeks |
| Jun | 68°F | 64°F | 🔥 Peak | ~8 weeks |
| Jul | 77°F | 71°F | 🔥 Peak | ~8 weeks |
| Aug | 78°F | 74°F | 🔥 Peak | ~8 weeks |
| Sep | 69°F | 70°F | 🔥 Peak | ~8 weeks |
| Oct | 57°F | 61°F | ♻️ Active | ~14 weeks |
| Nov | 41°F | 49°F | 🐢 Slow | ~24 weeks |
| Dec | 29°F | 37°F | ❄️ Dormant | ~36 weeks |
Highlighted rows = soil 60°F+ (safe for warm-season transplants). Compost finishes fastest during peak activity months.
Pest & Disease Pressure in Audubon County
Computed from local climate patterns — warmer, humid conditions increase pest generations and fungal disease risk.
Why it matters: In Audubon County's climate, pest pressure shapes which crops are easy and which are heartbreak. Tomatoes are easy in dry mountain air, hard in humid coast — same plant, completely different gardening experience.
Insect Pest Pressure
Moderate — common pests appear but manageable with monitoring.
Disease Risk
Low disease risk — dry conditions reduce fungal problems.
Seasonal Risk
View 5 common pests in your area
| Pest | Risk Level | Peak Months |
|---|---|---|
| Aphids | Moderate | May, Jun, Jul, Aug |
| Japanese beetles | Moderate | Jun, Jul, Aug |
| Squash bugs | Low | Jun, Jul, Aug |
| Tomato hornworms | Moderate | Jul, Aug |
| Cabbage loopers | Low | May, Jun, Jul, Aug |
Organic pest management tips
- Maintain healthy soil with regular compost additions to build natural pest resistance
- Practice crop rotation annually to break pest cycles
- Encourage beneficial insects with flowering herbs like dill, fennel, and yarrow
Cover Crops for Audubon County
Cover crops protect bare soil, fix nitrogen, suppress weeds, and improve soil structure — with planting dates calibrated for your area.
Why it matters: Cover crops do four things at once: fix nitrogen (legumes), suppress weeds (any), prevent erosion, and add organic matter when chopped down. Audubon County's seasonal pattern determines which species fit which gap.
Spring Cover Crops (3 options) — Build soil before the main growing season
| Crop | Plant By | Terminate | N-Fixing | Soil Benefit |
|---|---|---|---|---|
| Buckwheat | May 7 | Jul 25 | — | Rapid growth, attracts pollinators, suppresses weeds |
| Sorghum-sudan grass | May 6 | Aug 8 | — | Massive biomass, breaks compaction, suppresses nematodes |
| White clover | Mar 31 | Jul 25 | ✓ Yes | Living mulch, fixes nitrogen, permanent ground cover |
Summer Cover Crops (1 options) — Fill gaps and suppress weeds between plantings
| Crop | Plant By | Terminate | N-Fixing | Soil Benefit |
|---|---|---|---|---|
| Sunflowers | May 28 | Sep 19 | — | Deep roots break compaction, attract pollinators and beneficial insects |
Fall Cover Crops (6 options) — Plant after harvest to protect soil over winter
| Crop | Plant By | Terminate | N-Fixing | Soil Benefit |
|---|---|---|---|---|
| Austrian winter peas | Jul 28 | Apr 7 | ✓ Yes | Fixes nitrogen, good for heavy clay soils |
| Daikon radish | Aug 15 | Apr 14 | — | Deep taproot breaks compaction, excellent for clay soils |
| Hairy vetch | Jul 23 | Apr 7 | ✓ Yes | Excellent nitrogen fixer, good for depleted soils |
| Oats | Sep 4 | Apr 14 | — | Quick biomass, winterkills in cold zones — no spring tillage needed |
| Winter rye | Jun 25 | Apr 7 | — | Suppresses weeds, prevents erosion, breaks up compacted soil |
| Winter wheat | Jun 29 | Apr 14 | — | Erosion control, weed suppression, good biomass |
Wind & Microclimate in Audubon County
Why this matters: Wind is the silent water thief. Every breeze pulls moisture from leaves and soil. Audubon County's 8.6 mph average is one piece of the watering math: rainfall + irrigation must exceed evaporation + transpiration, and wind boosts both losses.
Wind dries soil, stresses plants, and affects frost patterns. Understanding your exposure helps with garden placement.
Seasonal Wind Speed
Spring: 11 mph Summer: 9 mph
Fall: 9 mph Winter: 13 mph
Prevailing wind: SW. Moderate wind — consider a temporary windbreak for young seedlings.
Windbreak Benefit
4.6/10
Moderately beneficial — a simple fence or trellis can protect delicate crops from wind stress.
Frost Pocket Risk
Low
Relatively flat terrain (261 ft range). Frost pocket risk is minimal — garden placement is flexible.
Rainwater Harvesting in Audubon County
How much water you can collect, when to collect it, and what size system you need for your garden.
For new gardeners: Most gardens use 0.5-1 gallon per square foot per week in summer. Audubon County's 33" annual rainfall is enough to cover most needs if you can capture it. Rain barrels under downspouts are the simplest entry point.
Annual Collection
16,148 gal
Per 1,000 sq ft of roof area (at 80% collection efficiency)
Recommended Setup
6 rain barrels (55 gal each)
For a typical 500 sq ft garden. Serious collectors: consider a 1,750 gal tank.
Legal Status
Unrestricted
Rainwater harvesting is fully legal in your state with no restrictions.
Best Collection Months
May, Jun, Jul, Aug
Highest rainfall months — your barrels will fill up quickly during these months.
Months to Draw From Storage
Jan, Feb, Dec
Dry months when you'll rely on stored water — size your storage for this gap.
Rainwater collection tips for your area
- Your county receives approximately 32.4 inches of rain per year
- A 1,000 sq ft roof can collect roughly 16,148 gallons annually
- Rainwater harvesting is fully legal in your state
- Stock up on stored water before your dry season (Jan, Feb, Dec)
- Use a first-flush diverter to keep roof debris out of your collection
Soil & Growing Conditions in Audubon County
Soil Type
Silt Loam
Soil pH 5.8–6.8 · Well Drained drainage
Native soil is well-suited to most vegetables and herbs with regular compost additions.
Watering Needs
Drought stress: 5.5/10
Moderate drought pressure. Drip irrigation and mulching are highly recommended to maintain soil moisture through summer.
Season Tips
158-day frost-free season
Start warm-season crops indoors and focus on short-season varieties. Cold frames extend your season by 3–4 weeks in fall.
Your Free Printable Garden Planner
Plan every bed, every planting, every harvest — in one place. This 22-page printable includes your zone's planting calendar, a month-by-month task list, a seed inventory tracker, a harvest log, and succession-planting charts. Built to print, write in, and actually use all season.
Recommended for Your Garden
Test your soil pH, nitrogen, phosphorus, and potassium levels before planting.
Get instant, accurate soil pH readings to fine-tune your amendments.
Boost soil fertility and structure with rich, well-aged organic compost.
Monthly Planting Guide for Audubon County
Gardening Guides & Resources
Helpful guides from The Ultimate Homestead to improve your garden in Audubon County.
Frequently Asked Questions
What planting zone is Audubon County, IA?
Audubon County is in USDA Hardiness Zone 5a. This zone classification determines which perennial plants survive winter and sets the baseline for frost timing across the county.
When is the last frost in Audubon County, IA?
Based on 31 years of NOAA weather station data, the median last spring frost in Audubon County falls around April 28. In 8 out of 10 years, last frost lands between April 18 and May 14 — a 26-day window of variability. Use May 14 as your conservative safe-to-plant date for frost-sensitive crops.
When is the first fall frost in Audubon County, IA?
The median first fall frost in Audubon County arrives around October 3. In cold years it can arrive as early as September 19; in mild years as late as October 15. Harvest or protect frost-sensitive crops — tomatoes, peppers, basil, squash — before this date.
How long is the growing season in Audubon County?
Audubon County has a frost-free growing season of approximately 158 days. This is enough time for most warm-season crops including tomatoes, peppers, and squash with proper timing. Climate records show the growing season is trending shorter by about 0.51 days per decade.
What is the soil like in Audubon County for gardening?
Audubon County has predominantly Silt Loam soil with a pH range of 5.8–6.8 and Well Drained drainage. Most vegetables and herbs grow well with standard composting and seasonal soil amendment.
What is grown commercially in Audubon County?
Audubon County has commercial agriculture that includes Soybeans, Corn, Hay, Wheat. These crops reflect the local climate and soil conditions — what succeeds commercially often translates well to home gardens in the same area.
Is Audubon County a good location for home gardening?
Audubon County scores 71/100 (Good) on our Microclimate Index, which combines frost reliability, drought pressure, soil challenge, elevation risk, and long-term climate trend. This is an above-average location for home gardening with relatively predictable growing conditions.
Your Audubon County Garden Planner — Free
A 22-page printable planner built for Audubon 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.
The Gardener's Encyclopedia to Companion Planting
The pairings that make vegetables, herbs, and flowers grow better — and the ones that quietly wreck a bed.
- Proven pairings for 200+ vegetables, herbs, flowers, and fruits
- Full seed-starting + planting schedule with timing and spacing
- Bonus: square-foot gardening guide + printable seasonal planners
Seed Saving & Storage Guide
Most saved seeds go bad before next season. This shows exactly when to pick, how to dry, and where to store seeds from 200 plants so yours don't.
- 200 plants, step-by-step: life cycle, pollination type, isolation
- Exact temperature + humidity ranges that keep seeds viable
- Bonus: searchable Google Sheets tracker + custom GPT assistant
Composting Guide for Homesteaders
Turn kitchen scraps and yard waste into compost that actually feeds the garden — instead of a pile that smells, attracts pests, and never breaks down.
- 14 sections on composting methods, soil science, and troubleshooting
- The 7-step hot-compost system from start to finish
- Bonus tools: troubleshooting chart, safety guide, monitoring log