Polk County, WI — Planting Guide
Polk County is in USDA Zone 4a. The average last spring frost is May 12 and the first fall frost is September 29, giving you a growing season of approximately 140 days.
At an elevation of 582 ft, Polk County receives approximately 40 in of rainfall annually. Summer highs average 82°F with winter lows around 7°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 24 in warm years to May 20 in cold years. The growing season is trending longer by about 0.75 days per decade. Polk County scores 69/100 (Good) on the Microclimate Index.
🌡️ Zone
4a (-30°F to -25°F min)
❄️ Last Frost
May 12
🍂 First Frost
September 29
📅 Growing Season
140 days
⛰️ Elevation
582 ft
🌧️ Annual Rainfall
40 in
Monthly Watering Calendar
When you'll need to water your garden — based on average monthly rainfall vs. the ~1 inch/week most gardens need.
View detailed monthly data
| Month | Avg Rainfall | Rainy Days | Extra Water Needed | Watering Effort |
|---|---|---|---|---|
| Jan | 1.6 in | 7 days | — | None |
| Feb | 2 in | 6 days | — | None |
| Mar | 2.8 in | 9 days | — | None |
| Apr | 3.8 in | 9 days | 0.5 in | Low |
| May | 4.7 in | 10 days | — | Low |
| Jun | 5.3 in | 10 days | — | Low |
| Jul | 4.6 in | 10 days | — | Low |
| Aug | 4.2 in | 8 days | 0.1 in | Low |
| Sep | 3.3 in | 8 days | 1 in | Moderate |
| Oct | 2.8 in | 7 days | 1.5 in | Moderate |
| Nov | 2.6 in | 8 days | — | None |
| Dec | 2.3 in | 7 days | — | None |
Annual total: 40 in. Gardens typically need ~1 inch of water per week during the growing season. Months marked "None" for extra water are outside the active growing season for your zone — most gardens are dormant and don't need irrigation during those months.
Polk County Soil Profile
Soil Type
Silt Loam
Soil pH
6-6.9
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 20 | Oct 13 | 146 days |
| Cautious | May 16 | Oct 8 | 145 days |
| Average year | May 12 | Sep 29 | 140 days |
| Optimistic | Apr 30 | Sep 24 | 147 days |
| Aggressive (risky) | Apr 24 | Sep 14 | 143 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 longer (0.8 days/decade). Historical frost dates are still reliable for planning.
Gardening Difficulty Score
Polk County offers good growing conditions. A little planning around frost dates goes a long way.
Local Gardening Help in Polk 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 Polk County's climate and soil.
County Extension Office
Polk County University of Wisconsin-Madison Division of Extension Extension Office
Phone: 608-263-7779
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 Polk County
Finding local nurseries & garden centers in Polk County
Why Buy Local
Local nurseries carry plants that are proven to grow in your area. Staff can give you advice specific to Polk 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 Polk County WI" or "garden center Polk 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 Polk County WI" or check your extension office and local parks department. Facebook groups like "Polk County Gardeners" or "Wisconsin 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
Monthly daylight hours and peak sun — critical for onion varieties, photoperiod-sensitive plants, and solar garden planning.
Longest Day
15.5 hours
Summer solstice daylight
Shortest Day
8.5 hours
Winter solstice daylight
Peak Sun Hours
9.9 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 | 8.9 hr | 3.5 hr | Short day |
| February | 10.1 hr | 4.4 hr | Short day |
| March | 11.6 hr | 5.8 hr | Short day |
| April | 13.3 hr | 6.6 hr | Neutral |
| May | 14.7 hr | 8.5 hr | Long day |
| June | 15.5 hr | 9.9 hr | Long day |
| July | 15.1 hr | 9.8 hr | Long day |
| August | 13.9 hr | 8.5 hr | Neutral |
| September | 12.3 hr | 7.2 hr | Neutral |
| October | 10.7 hr | 5.6 hr | Short day |
| November | 9.2 hr | 3.8 hr | Short day |
| December | 8.5 hr | 3.3 hr | Short day |
Peak sun hours factor in typical cloud cover — use these for solar panel and shade-planning calculations.
Soil Temperature & Composting Calendar
Monthly soil temps tell you when to plant warm-season crops, and when your compost pile is actively working.
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 | 14°F | 23°F | ❄️ Dormant | ~36 weeks |
| Feb | 18°F | 21°F | ❄️ Dormant | ~36 weeks |
| Mar | 26°F | 30°F | ❄️ Dormant | ~36 weeks |
| Apr | 41°F | 39°F | 🐢 Slow | ~24 weeks |
| May | 55°F | 50°F | ♻️ Active | ~14 weeks |
| Jun | 66°F | 60°F | 🔥 Peak | ~8 weeks |
| Jul | 73°F | 67°F | 🔥 Peak | ~8 weeks |
| Aug | 74°F | 67°F | 🔥 Peak | ~8 weeks |
| Sep | 65°F | 65°F | ♻️ Active | ~14 weeks |
| Oct | 51°F | 54°F | ♻️ Active | ~14 weeks |
| Nov | 37°F | 44°F | ❄️ Dormant | ~36 weeks |
| Dec | 23°F | 31°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 Polk County
Computed from local climate patterns — warmer, humid conditions increase pest generations and fungal disease risk.
Insect Pest Pressure
Moderate — common pests appear but manageable with monitoring.
Disease Risk
Moderate — watch for mildew and blight during wet periods.
Seasonal Risk
View 5 common pests in your area
| Pest | Risk Level | Peak Months |
|---|---|---|
| Aphids | Moderate | May, Jun, Jul, Aug |
| Cabbage worms | Low | Jun, Jul, Aug |
| Colorado potato beetle | Moderate | Jun, Jul |
| Flea beetles | Moderate | May, Jun, Jul |
| Slugs | Low | May, Jun, Jul, Aug, Sep |
Organic pest management tips
- Use row covers on susceptible crops during peak pest months
- Apply neem oil preventatively every 7-14 days during active pest season
- Interplant with strong-scented herbs (basil, marigold) to confuse pests
- Hand-pick larger pests (beetles, caterpillars) in early morning when they're sluggish
- Practice crop rotation — never plant the same family in the same spot within 3 years
Cover Crops for Polk County
Cover crops protect bare soil, fix nitrogen, suppress weeds, and improve soil structure — with county-specific planting dates.
Fall Cover Crops (5 options) — Plant after harvest to protect soil over winter
| Crop | Plant By | Terminate | N-Fixing | Soil Benefit |
|---|---|---|---|---|
| Daikon radish | Aug 14 | Apr 21 | — | Deep taproot breaks compaction, excellent for clay soils |
| Hairy vetch | Jul 12 | Apr 28 | ✓ Yes | Excellent nitrogen fixer, good for depleted soils |
| Oats | Sep 2 | Apr 21 | — | Quick biomass, winterkills in cold zones — no spring tillage needed |
| Winter rye | Jul 7 | Apr 21 | — | Suppresses weeds, prevents erosion, breaks up compacted soil |
| Winter wheat | Jun 26 | Apr 21 | — | Erosion control, weed suppression, good biomass |
Spring Cover Crops (2 options) — Build soil before the main growing season
| Crop | Plant By | Terminate | N-Fixing | Soil Benefit |
|---|---|---|---|---|
| Buckwheat | May 18 | Jul 21 | — | Rapid growth, attracts pollinators, suppresses weeds |
| White clover | Apr 16 | Jul 21 | ✓ 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 | Jun 12 | Sep 15 | — | Deep roots break compaction, attract pollinators and beneficial insects |
Wind & Microclimate
Wind dries soil, stresses plants, and affects frost patterns. Understanding your exposure helps with garden placement.
Seasonal Wind Speed
Spring: 12 mph Summer: 9 mph
Fall: 11 mph Winter: 11 mph
Prevailing wind: SW. Moderate wind — consider a temporary windbreak for young seedlings.
Windbreak Benefit
5/10
Moderately beneficial — a simple fence or trellis can protect delicate crops from wind stress.
Frost Pocket Risk
Low
Relatively flat terrain (256 ft range). Frost pocket risk is minimal — garden placement is flexible.
Rainwater Harvesting Potential
How much water you can collect, when to collect it, and what size system you need for your garden.
Annual Collection
19,936 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 1,500 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 40.0 inches of rain per year
- A 1,000 sq ft roof can collect roughly 19,936 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 Polk County
Soil Type
Silt Loam
Soil pH 6–6.9 · 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
140-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.
Free Garden Planner
Plan your entire garden season — organize planting dates, track what you're growing, and know exactly when to start seeds, transplant, and harvest.
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.
🥬 Vegetables to Grow in Polk County
96 vegetables that grow well in Zone 4a with planting dates for Polk County.
Show all 96 vegetables with planting dates
| Plant | Start Indoors | Direct Sow | Transplant | Harvest | Days to Maturity |
|---|---|---|---|---|---|
| Acorn Squash | Mar 31 | May 26 | Jun 2 | Aug 25 – Sep 29 | 80–100 |
| Amaranth | Mar 10 | May 26 | Jun 2 | Sep 1 – Oct 20 | 90–120 |
| Arugula | Mar 31 | May 5 | May 12 | Jun 16 – Aug 18 | 30–50 |
| Asparagus | — | — | May 26 | — | 730–1095 |
| Beets | — | May 5 | — | Jun 30 – Jul 28 | 50–70 |
| Belgian Endive | Mar 31 | May 5 | May 12 | Sep 1 – Oct 6 | 110–150 |
| Black Beans | — | May 26 | — | Aug 25 – Oct 13 | 90–120 |
| Bok Choy | Mar 31 | May 5 | May 12 | Jun 23 – Jul 28 | 40–60 |
| Broccoli | Mar 31 | May 5 | May 12 | Jul 14 – Aug 25 | 60–90 |
| Broccoli Rabe | Mar 31 | May 5 | May 12 | Jun 23 – Jul 28 | 40–60 |
| Brussels Sprouts | Mar 31 | May 5 | May 12 | Aug 11 – Oct 6 | 90–130 |
| Butternut Squash | Mar 31 | May 26 | Jun 2 | Sep 1 – Oct 6 | 85–110 |
| Cabbage | Mar 31 | May 5 | May 12 | Jul 14 – Sep 8 | 60–100 |
| Carrots | — | May 5 | — | Jul 7 – Aug 11 | 60–80 |
| Cauliflower | Mar 31 | May 5 | May 12 | Jul 7 – Sep 8 | 55–100 |
| Celeriac | Mar 31 | May 5 | May 12 | Aug 25 – Sep 29 | 100–120 |
| Celery | Mar 31 | May 5 | May 12 | Aug 4 – Sep 29 | 80–120 |
| Celtuce | Mar 31 | May 5 | May 12 | Jul 14 – Aug 25 | 60–90 |
| Chard | Mar 31 | May 5 | May 12 | Jul 7 – Aug 25 | 50–60 |
| Chickpeas | Mar 31 | May 5 | May 12 | Aug 4 – Sep 15 | 80–110 |
| Chicory | Mar 31 | May 5 | May 12 | Jul 14 – Aug 25 | 60–85 |
| Chinese Cabbage | Mar 31 | May 5 | May 12 | Jul 7 – Aug 4 | 50–70 |
| Christmas Lima Beans | Mar 10 | May 26 | Jun 2 | Aug 25 – Sep 29 | 80–100 |
| Collard Greens | Mar 31 | May 5 | May 12 | Jul 7 – Sep 8 | 55–75 |
| Corn | — | May 26 | — | Jul 28 – Sep 22 | 60–100 |
| Cress | Mar 31 | May 5 | May 12 | May 26 – Jun 16 | 14–21 |
| Crookneck Squash | Mar 31 | May 26 | Jun 2 | Jul 21 – Aug 18 | 45–60 |
| Crosne | — | May 5 | — | Oct 6 – Sep 29 | 150–200 |
| Cucumber | Mar 31 | May 26 | Jun 2 | Jul 28 – Sep 22 | 50–70 |
| Daikon | — | May 5 | — | Jun 30 – Jul 28 | 50–70 |
| Delicata Squash | Mar 31 | May 26 | Jun 2 | Aug 25 – Sep 29 | 80–100 |
| Edamame | — | May 26 | — | Aug 11 – Sep 22 | 75–100 |
| Endive | Mar 31 | May 5 | May 12 | Jun 30 – Aug 4 | 45–65 |
| Escarole | Mar 31 | May 5 | May 12 | Jul 7 – Aug 4 | 50–70 |
| Fava Beans | Mar 31 | May 5 | May 12 | Jul 28 – Sep 8 | 75–100 |
| Fennel | Mar 10 | May 26 | Jun 2 | Aug 4 – Sep 15 | 60–90 |
| Garlic | — | — | — | — | 90–240 |
| Green Beans | — | May 26 | — | Jul 21 – Sep 15 | 50–65 |
| Horseradish | — | — | May 26 | Sep 29 – Oct 20 | 120–180 |
| Hubbard Squash | Mar 31 | May 26 | Jun 2 | Sep 15 – Oct 20 | 100–120 |
| Kabocha | Mar 31 | May 26 | Jun 2 | Sep 1 – Sep 29 | 85–100 |
| Kai Lan | Mar 31 | May 5 | May 12 | Jun 30 – Jul 28 | 45–60 |
| Kale | Mar 31 | May 5 | May 12 | Jul 7 – Sep 1 | 50–70 |
| Kidney Beans | — | May 26 | — | Aug 25 – Sep 29 | 85–110 |
| Kohlrabi | Mar 31 | May 5 | May 12 | Jun 30 – Aug 4 | 45–65 |
| Komatsuna | Mar 31 | May 5 | May 12 | Jun 16 – Jul 21 | 35–50 |
| Leeks | Mar 31 | May 5 | May 12 | Aug 11 – Oct 6 | 90–150 |
| Lentils | Mar 31 | May 5 | May 12 | Aug 4 – Sep 15 | 80–110 |
| Lettuce | Mar 31 | May 5 | May 12 | Jun 16 – Aug 25 | 30–60 |
| Lima Beans | — | May 26 | — | Jul 28 – Sep 8 | 60–90 |
| Mache | Mar 31 | May 5 | May 12 | Jun 23 – Jul 28 | 40–60 |
| Melon | Mar 31 | May 26 | Jun 2 | Aug 11 – Sep 29 | 70–100 |
| Microgreens | Mar 31 | May 5 | May 12 | May 19 – Jun 16 | 7–21 |
| Mitsuba | Mar 31 | May 5 | May 5 | Jun 30 – Aug 25 | 50–70 |
| Mizuna | Mar 31 | May 5 | May 12 | Jun 16 – Jul 14 | 30–45 |
| Mustard Greens | Mar 31 | May 5 | May 12 | Jun 16 – Aug 18 | 30–50 |
| Napa Cabbage | Mar 31 | May 5 | May 12 | Jul 7 – Aug 11 | 55–75 |
| Onion | Mar 31 | May 5 | May 12 | Aug 11 – Sep 29 | 90–120 |
| Pac Choi | Mar 31 | May 5 | May 12 | Jun 23 – Jul 21 | 40–55 |
| Parsnip | — | May 5 | — | Aug 18 – Sep 29 | 100–130 |
| Patty Pan Squash | Mar 31 | May 26 | Jun 2 | Jul 21 – Aug 18 | 45–60 |
| Peas | Mar 31 | May 5 | May 12 | Jul 7 – Sep 1 | 55–70 |
| Peppers | Feb 24 | May 26 | Jun 2 | Aug 4 – Oct 13 | 60–90 |
| Pole Beans | Mar 10 | May 26 | Jun 2 | Jul 28 – Sep 22 | 55–70 |
| Potatoes | Mar 10 | May 26 | Jun 2 | Aug 11 – Oct 20 | 70–120 |
| Pumpkin | Mar 31 | May 26 | Jun 2 | Sep 1 – Oct 20 | 85–120 |
| Purslane | Mar 31 | May 5 | May 12 | Jun 23 – Jul 28 | 40–60 |
| Radicchio | Mar 31 | May 5 | May 12 | Jul 14 – Aug 18 | 60–80 |
| Radish | — | May 5 | — | Jun 2 – Jun 23 | 22–35 |
| Rhubarb | — | — | Jun 9 | — | 365–730 |
| Romanesco | Mar 31 | May 5 | May 12 | Jul 28 – Sep 8 | 75–100 |
| Rutabaga | — | May 5 | — | Jul 28 – Sep 1 | 80–100 |
| Salsify | — | May 5 | — | Aug 18 – Sep 29 | 100–130 |
| Savoy Cabbage | Mar 31 | May 5 | May 12 | Jul 21 – Sep 15 | 70–110 |
| Scallions | Mar 31 | May 5 | May 12 | Jul 7 – Aug 4 | 50–70 |
| Scarlet Runner Beans | Mar 10 | May 26 | Jun 2 | Aug 4 – Sep 8 | 60–80 |
| Shallot | Mar 31 | May 5 | May 12 | Aug 11 – Sep 29 | 90–120 |
| Shiso | Mar 17 | May 19 | Jun 2 | Jul 28 – Sep 22 | 50–70 |
| Snap Peas | Mar 10 | May 26 | Jun 2 | Jul 28 – Sep 22 | 55–70 |
| Snow Peas | Mar 31 | May 5 | May 12 | Jul 7 – Sep 1 | 50–65 |
| Soybeans | — | May 26 | — | Aug 18 – Oct 13 | 80–120 |
| Spaghetti Squash | Mar 31 | May 26 | Jun 2 | Sep 1 – Sep 29 | 85–100 |
| Spinach | Mar 31 | May 5 | May 12 | Jun 16 – Aug 18 | 35–50 |
| Squash (Summer) | Mar 31 | May 26 | Jun 2 | Jul 21 – Sep 22 | 45–65 |
| Squash (Winter) | Mar 31 | May 26 | Jun 2 | Aug 25 – Oct 20 | 80–120 |
| Sunchoke | — | — | May 26 | Sep 15 – Oct 20 | 110–150 |
| Sunflower | Mar 10 | May 26 | Jun 2 | Aug 11 – Sep 29 | 70–100 |
| Sweet Corn | — | May 26 | — | Jul 28 – Sep 8 | 60–90 |
| Tatsoi | Mar 31 | May 5 | May 12 | Jun 16 – Jul 21 | 35–50 |
| Tomatillo | Mar 10 | May 26 | Jun 2 | Aug 4 – Oct 13 | 60–85 |
| Tomatoes | Mar 10 | May 26 | Jun 2 | Aug 4 – Oct 13 | 60–85 |
| Turnip | — | May 5 | — | Jun 16 – Jul 21 | 40–60 |
| Watercress | Mar 31 | May 5 | May 12 | Jun 23 – Jul 28 | 40–60 |
| Watermelon | Mar 31 | May 26 | Jun 2 | Aug 11 – Sep 29 | 70–100 |
| Wax Beans | — | May 26 | — | Jul 21 – Sep 15 | 50–65 |
| Zucchini | Mar 31 | May 26 | Jun 2 | Jul 21 – Sep 15 | 45–60 |
🍓 Fruits to Grow in Polk County
22 fruits that grow well in Zone 4a with planting dates for Polk County.
Show all 22 fruits with planting dates
| Plant | Start Indoors | Direct Sow | Transplant | Harvest | Days to Maturity |
|---|---|---|---|---|---|
| Alpine Strawberries | — | — | Jun 9 | Sep 8 – Nov 3 | 90–180 |
| Aronia | — | — | Jun 9 | — | 730–1095 |
| Blueberries | — | — | Jun 9 | — | 730–1095 |
| Cantaloupe | — | — | Jun 9 | Aug 18 – Sep 22 | 70–90 |
| Cranberries | — | — | Jun 9 | — | 730–1095 |
| Currants | — | — | Jun 9 | — | 730–1095 |
| Elderberries | — | — | Jun 9 | — | 730–1095 |
| Goji Berries | — | — | Jun 9 | — | 730–1095 |
| Gooseberries | — | — | Jun 9 | — | 730–1095 |
| Grapes | — | — | Jun 9 | — | 730–1095 |
| Ground Cherry | — | — | Jun 9 | Aug 18 – Oct 13 | 65–80 |
| Hardy Kiwi | — | — | Jun 9 | — | 1095–1825 |
| Haskaps | — | — | Jun 9 | — | 730–1095 |
| Honeydew | — | — | Jun 9 | Sep 1 – Oct 13 | 80–110 |
| Jostaberry | — | — | Jun 9 | — | 730–1095 |
| Lingonberries | — | — | Jun 9 | — | 730–1095 |
| Medlar | — | — | Jun 9 | — | 1095–1825 |
| Mulberries | — | — | Jun 9 | — | 730–1825 |
| Persimmon | — | — | Jun 9 | — | 1095–2555 |
| Raspberries | — | — | Jun 9 | — | 365–730 |
| Serviceberries | — | — | Jun 9 | — | 730–1095 |
| Strawberries | — | — | Jun 9 | Sep 8 – Nov 3 | 90–365 |
🌿 Herbs to Grow in Polk County
32 herbs that grow well in Zone 4a with planting dates for Polk County.
Show all 32 herbs with planting dates
| Plant | Start Indoors | Direct Sow | Transplant | Harvest | Days to Maturity |
|---|---|---|---|---|---|
| Angelica | Mar 31 | May 5 | May 5 | — | 365–730 |
| Anise | Mar 31 | May 5 | May 5 | Aug 4 – Sep 29 | 90–120 |
| Basil | Mar 17 | May 19 | Jun 2 | Jul 28 – Sep 29 | 50–75 |
| Bee Balm | — | — | May 19 | Aug 18 – Oct 13 | 90–120 |
| Borage | Mar 31 | May 5 | May 5 | Jun 30 – Aug 18 | 50–60 |
| Caraway | Mar 31 | May 5 | May 5 | — | 365–450 |
| Catnip | — | — | May 19 | Jul 21 – Sep 22 | 60–80 |
| Chamomile | Mar 31 | May 5 | May 5 | Jul 7 – Sep 15 | 60–90 |
| Chervil | Mar 31 | May 5 | May 5 | Jun 16 – Aug 18 | 40–60 |
| Chives | — | — | May 19 | Jul 21 – Sep 29 | 60–90 |
| Cilantro | Mar 31 | May 5 | May 5 | Jun 16 – Aug 18 | 40–60 |
| Comfrey | — | — | May 19 | Jul 21 – Sep 29 | 60–90 |
| Dill | Mar 31 | May 5 | May 5 | Jun 16 – Aug 18 | 40–60 |
| Echinacea | — | — | May 19 | Sep 22 – Oct 13 | 120–180 |
| Fennel (herb) | Mar 31 | May 5 | May 5 | Jul 7 – Sep 15 | 60–90 |
| Garlic Chives | — | — | May 19 | Jul 21 – Sep 29 | 60–90 |
| Horehound | — | — | May 19 | Aug 4 – Sep 29 | 75–90 |
| Hyssop | — | — | May 19 | Jul 28 – Sep 29 | 70–90 |
| Lemon Balm | — | — | May 19 | Jul 21 – Sep 8 | 60–70 |
| Lovage | — | — | May 19 | Jul 28 – Sep 29 | 70–90 |
| Mint | — | — | May 19 | Jul 21 – Sep 29 | 60–90 |
| Oregano | — | — | May 19 | Jul 21 – Sep 29 | 60–90 |
| Parsley | Mar 31 | May 5 | May 5 | Jul 7 – Sep 8 | 60–80 |
| Rue | — | — | May 19 | Jul 28 – Sep 29 | 70–90 |
| Sage | — | — | May 19 | Aug 4 – Sep 29 | 75–90 |
| Savory | — | — | May 19 | Jul 14 – Sep 8 | 50–70 |
| Sorrel | Mar 31 | May 5 | May 5 | Jun 16 – Aug 18 | 40–60 |
| Tarragon | — | — | May 19 | Jul 21 – Sep 29 | 60–90 |
| Thai Basil | Mar 17 | May 19 | Jun 2 | Jul 28 – Sep 29 | 50–75 |
| Thyme | — | — | May 19 | Jul 28 – Sep 29 | 70–90 |
| Valerian | — | — | May 19 | Sep 22 – Oct 13 | 120–180 |
| Yarrow | — | — | May 19 | Aug 18 – Oct 13 | 90–120 |
Monthly Planting Guide for Polk County
Gardening Guides & Resources
Helpful guides from The Ultimate Homestead to improve your garden in Polk County.
Frequently Asked Questions
What planting zone is Polk County, WI?
Polk County is in USDA Hardiness Zone 4a. 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 Polk County, WI?
Based on 31 years of NOAA weather station data, the median last spring frost in Polk County falls around May 12. In 8 out of 10 years, last frost lands between April 24 and May 20 — a 26-day window of variability. Use May 20 as your conservative safe-to-plant date for frost-sensitive crops.
When is the first fall frost in Polk County, WI?
The median first fall frost in Polk County arrives around September 29. In cold years it can arrive as early as September 14; in mild years as late as October 13. Harvest or protect frost-sensitive crops — tomatoes, peppers, basil, squash — before this date.
How long is the growing season in Polk County?
Polk County has a frost-free growing season of approximately 140 days. Focus on short-season varieties and start warm-season crops indoors 6–8 weeks before last frost. Climate records show the growing season is trending longer by about 0.75 days per decade.
What is the soil like in Polk County for gardening?
Polk County has predominantly Silt Loam soil with a pH range of 6–6.9 and Well Drained drainage. Most vegetables and herbs grow well with standard composting and seasonal soil amendment.
What is grown commercially in Polk County?
Polk County has commercial agriculture that includes Soybeans, Corn, Hay, Dairy, Oats. These crops reflect the local climate and soil conditions — what succeeds commercially often translates well to home gardens in the same area.
Is Polk County a good location for home gardening?
Polk County scores 69/100 (Good) on our Microclimate Index, which combines frost reliability, drought pressure, soil challenge, elevation risk, and long-term climate trend. Conditions here are moderate — most common crops grow well with standard timing and care.
Plan Your Garden with Confidence
Get our free Garden Planner — designed to help Polk County gardeners in Zone 4a organize planting dates, track what's growing, and never miss a planting window.
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