Knox County, IL — Planting Guide
Knox County is in USDA Zone 5a. 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 ft, Knox County receives approximately 33.2 in of rainfall annually. Summer highs average 84°F with winter lows around 16°F. The predominant soil type is Silt Loam.
Based on 31 years of NOAA climate station data, the last frost date here varies by 28 days year to year — ranging from April 4 in warm years to May 3 in cold years. The growing season is trending shorter by about 2.83 days per decade. Knox County scores 56/100 (Moderate) on the Microclimate Index.
🌡️ Zone
5a (-20°F to -15°F min)
❄️ Last Frost
April 17
🍂 First Frost
October 15
📅 Growing Season
181 days
⛰️ Elevation
1,301 ft
🌧️ Annual Rainfall
33.2 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 | 1.3 in | 7 days | — | None |
| Feb | 1.5 in | 7 days | — | None |
| Mar | 2.4 in | 8 days | — | None |
| Apr | 3.4 in | 9 days | 0.9 in | Moderate |
| May | 3.9 in | 9 days | 0.4 in | Low |
| Jun | 3.6 in | 8 days | 0.7 in | Moderate |
| Jul | 4.1 in | 9 days | 0.2 in | Low |
| Aug | 3.5 in | 9 days | 0.8 in | Moderate |
| Sep | 2.6 in | 7 days | 1.7 in | High |
| Oct | 2.7 in | 9 days | 1.6 in | High |
| Nov | 2.5 in | 7 days | — | None |
| Dec | 1.6 in | 9 days | — | None |
Annual total: 33.1 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.
Knox County Soil Profile
Soil Type
Silt Loam
Soil pH
6-6.8
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 3 | Nov 4 | 185 days |
| Cautious | Apr 25 | Oct 22 | 180 days |
| Average year | Apr 17 | Oct 15 | 181 days |
| Optimistic | Apr 12 | Oct 10 | 181 days |
| Aggressive (risky) | Apr 4 | Oct 2 | 181 days |
Not very — frost dates can vary by ±28 days year-to-year. Use the "Conservative" row in the table below, and keep row covers handy for surprise late frosts.
Yes — growing seasons are getting shorter here (about 2.8 days per decade). Use the "Conservative" dates and choose fast-maturing varieties.
Gardening Difficulty Score
Knox County presents some gardening challenges. Choose adapted varieties and plan around frost dates.
Local Gardening Help in Knox 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 Knox County's climate and soil.
County Extension Office
Knox County University of Illinois Extension Extension Office
Phone: 217-333-7672
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 Knox County
Finding local nurseries & garden centers in Knox County
Why Buy Local
Local nurseries carry plants that are proven to grow in your area. Staff can give you advice specific to Knox 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 Knox County IL" or "garden center Knox 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 Knox County IL" or check your extension office and local parks department. Facebook groups like "Knox County Gardeners" or "Illinois 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
14.9 hours
Summer solstice daylight
Shortest Day
9.1 hours
Winter solstice daylight
Peak Sun Hours
9.8 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 | 9.4 hr | 3.8 hr | Short day |
| February | 10.4 hr | 4.5 hr | Short day |
| March | 11.7 hr | 5.7 hr | Short day |
| April | 13.1 hr | 6.8 hr | Neutral |
| May | 14.3 hr | 8.5 hr | Long day |
| June | 14.9 hr | 9.1 hr | Long day |
| July | 14.7 hr | 9.8 hr | Long day |
| August | 13.6 hr | 8.3 hr | Neutral |
| September | 12.3 hr | 7.2 hr | Neutral |
| October | 10.9 hr | 5.4 hr | Short day |
| November | 9.7 hr | 3.8 hr | Short day |
| December | 9.1 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 | 22°F | 30°F | ❄️ Dormant | ~36 weeks |
| Feb | 23°F | 29°F | ❄️ Dormant | ~36 weeks |
| Mar | 32°F | 33°F | ❄️ Dormant | ~36 weeks |
| Apr | 46°F | 43°F | 🐢 Slow | ~24 weeks |
| May | 58°F | 53°F | ♻️ Active | ~14 weeks |
| Jun | 67°F | 62°F | 🔥 Peak | ~8 weeks |
| Jul | 78°F | 71°F | 🔥 Peak | ~8 weeks |
| Aug | 78°F | 73°F | 🔥 Peak | ~8 weeks |
| Sep | 69°F | 67°F | 🔥 Peak | ~8 weeks |
| Oct | 58°F | 61°F | ♻️ Active | ~14 weeks |
| Nov | 43°F | 48°F | 🐢 Slow | ~24 weeks |
| Dec | 28°F | 39°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 Knox 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
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 | Moderate | Jun, Jul, Aug |
| Tomato hornworms | Low | Jul, Aug |
| Cabbage loopers | Moderate | 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 Knox County
Cover crops protect bare soil, fix nitrogen, suppress weeds, and improve soil structure — with county-specific planting dates.
Spring Cover Crops (3 options) — Build soil before the main growing season
| Crop | Plant By | Terminate | N-Fixing | Soil Benefit |
|---|---|---|---|---|
| Buckwheat | Apr 22 | Aug 6 | — | Rapid growth, attracts pollinators, suppresses weeds |
| Sorghum-sudan grass | Apr 26 | Aug 6 | — | Massive biomass, breaks compaction, suppresses nematodes |
| White clover | Mar 19 | Aug 6 | ✓ 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 | Apr 28 | Oct 1 | — | 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 | Aug 9 | Mar 27 | ✓ Yes | Fixes nitrogen, good for heavy clay soils |
| Daikon radish | Aug 20 | Apr 3 | — | Deep taproot breaks compaction, excellent for clay soils |
| Hairy vetch | Jul 23 | Mar 27 | ✓ Yes | Excellent nitrogen fixer, good for depleted soils |
| Oats | Sep 20 | Apr 3 | — | Quick biomass, winterkills in cold zones — no spring tillage needed |
| Winter rye | Jul 23 | Mar 27 | — | Suppresses weeds, prevents erosion, breaks up compacted soil |
| Winter wheat | Jul 17 | Mar 27 | — | Erosion control, weed suppression, good biomass |
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: 10 mph Winter: 12 mph
Prevailing wind: SW. Moderate wind — consider a temporary windbreak for young seedlings.
Windbreak Benefit
5.3/10
Moderately beneficial — a simple fence or trellis can protect delicate crops from wind stress.
Frost Pocket Risk
Low
Relatively flat terrain (147 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
16,497 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 33.1 inches of rain per year
- A 1,000 sq ft roof can collect roughly 16,497 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 Knox County
Soil Type
Silt Loam
Soil pH 6–6.8 · 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
181-day frost-free season
Plenty of time for warm-season crops. Start heat-lovers indoors 6–8 weeks before last frost to maximise your harvest window.
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 Knox County
106 vegetables that grow well in Zone 5a with planting dates for Knox County.
Show all 106 vegetables with planting dates
| Plant | Start Indoors | Direct Sow | Transplant | Harvest | Days to Maturity |
|---|---|---|---|---|---|
| Acorn Squash | Mar 13 | Apr 24 | May 1 | Jul 24 – Aug 28 | 80–100 |
| Amaranth | Feb 20 | Apr 24 | May 1 | Jul 31 – Sep 18 | 90–120 |
| Arugula | Mar 13 | Apr 3 | Apr 17 | May 22 – Jul 24 | 30–50 |
| Asparagus | — | — | May 1 | — | 730–1095 |
| Beets | — | Apr 3 | — | May 29 – Jun 26 | 50–70 |
| Belgian Endive | Mar 13 | Apr 3 | Apr 17 | Aug 7 – Oct 2 | 110–150 |
| Bitter Melon | Feb 20 | Apr 24 | May 1 | Jul 3 – Aug 14 | 60–90 |
| Black Beans | — | Apr 24 | — | Jul 24 – Sep 11 | 90–120 |
| Bok Choy | Mar 13 | Apr 3 | Apr 17 | May 29 – Jul 3 | 40–60 |
| Broccoli | Mar 13 | Apr 3 | Apr 17 | Jun 19 – Jul 31 | 60–90 |
| Broccoli Rabe | Mar 13 | Apr 3 | Apr 17 | May 29 – Jul 3 | 40–60 |
| Brussels Sprouts | Mar 13 | Apr 3 | Apr 17 | Jul 17 – Sep 11 | 90–130 |
| Butternut Squash | Mar 13 | Apr 24 | May 1 | Jul 31 – Sep 4 | 85–110 |
| Cabbage | Mar 13 | Apr 3 | Apr 17 | Jun 19 – Aug 14 | 60–100 |
| Calabash | Feb 20 | Apr 24 | May 1 | Jul 24 – Sep 18 | 80–120 |
| Carrots | — | Apr 3 | — | Jun 5 – Jul 10 | 60–80 |
| Cauliflower | Mar 13 | Apr 3 | Apr 17 | Jun 12 – Aug 14 | 55–100 |
| Celeriac | Mar 13 | Apr 3 | Apr 17 | Jul 31 – Sep 4 | 100–120 |
| Celery | Mar 13 | Apr 3 | Apr 17 | Jul 10 – Sep 4 | 80–120 |
| Celtuce | Mar 13 | Apr 3 | Apr 17 | Jun 19 – Jul 31 | 60–90 |
| Chard | Mar 13 | Apr 3 | Apr 17 | Jun 12 – Jul 31 | 50–60 |
| Chickpeas | Mar 13 | Apr 3 | Apr 17 | Jul 10 – Aug 21 | 80–110 |
| Chicory | Mar 13 | Apr 3 | Apr 17 | Jun 19 – Jul 31 | 60–85 |
| Chinese Cabbage | Mar 13 | Apr 3 | Apr 17 | Jun 12 – Jul 10 | 50–70 |
| Christmas Lima Beans | Feb 20 | Apr 24 | May 1 | Jul 24 – Aug 28 | 80–100 |
| Collard Greens | Mar 13 | Apr 3 | Apr 17 | Jun 12 – Aug 14 | 55–75 |
| Corn | — | Apr 24 | — | Jun 26 – Aug 21 | 60–100 |
| Cowpeas | — | Apr 24 | — | Jun 26 – Aug 7 | 60–90 |
| Cress | Mar 13 | Apr 3 | Apr 17 | May 1 – May 22 | 14–21 |
| Crookneck Squash | Mar 13 | Apr 24 | May 1 | Jun 19 – Jul 17 | 45–60 |
| Crosne | — | Apr 3 | — | Sep 4 – Sep 18 | 150–200 |
| Cucumber | Mar 13 | Apr 24 | May 1 | Jun 26 – Aug 21 | 50–70 |
| Daikon | — | Apr 3 | — | May 29 – Jun 26 | 50–70 |
| Delicata Squash | Mar 13 | Apr 24 | May 1 | Jul 24 – Aug 28 | 80–100 |
| Edamame | — | Apr 24 | — | Jul 10 – Aug 21 | 75–100 |
| Eggplant | Feb 6 | Apr 24 | May 1 | Jul 10 – Sep 11 | 65–85 |
| Endive | Mar 13 | Apr 3 | Apr 17 | Jun 5 – Jul 10 | 45–65 |
| Escarole | Mar 13 | Apr 3 | Apr 17 | Jun 12 – Jul 10 | 50–70 |
| Fava Beans | Mar 13 | Apr 3 | Apr 17 | Jul 3 – Aug 14 | 75–100 |
| Fennel | Feb 20 | Apr 24 | May 1 | Jul 3 – Aug 14 | 60–90 |
| Garlic | — | — | — | — | 90–240 |
| Green Beans | — | Apr 24 | — | Jun 19 – Aug 14 | 50–65 |
| Horseradish | — | — | May 1 | Sep 4 – Oct 16 | 120–180 |
| Hot Peppers | Feb 6 | Apr 24 | May 1 | Jul 10 – Oct 16 | 70–120 |
| Hubbard Squash | Mar 13 | Apr 24 | May 1 | Aug 14 – Sep 18 | 100–120 |
| Kabocha | Mar 13 | Apr 24 | May 1 | Jul 31 – Aug 28 | 85–100 |
| Kai Lan | Mar 13 | Apr 3 | Apr 17 | Jun 5 – Jul 3 | 45–60 |
| Kale | Mar 13 | Apr 3 | Apr 17 | Jun 12 – Aug 7 | 50–70 |
| Kidney Beans | — | Apr 24 | — | Jul 24 – Aug 28 | 85–110 |
| Kohlrabi | Mar 13 | Apr 3 | Apr 17 | Jun 5 – Jul 10 | 45–65 |
| Komatsuna | Mar 13 | Apr 3 | Apr 17 | May 22 – Jun 26 | 35–50 |
| Leeks | Mar 13 | Apr 3 | Apr 17 | Jul 17 – Oct 2 | 90–150 |
| Lentils | Mar 13 | Apr 3 | Apr 17 | Jul 10 – Aug 21 | 80–110 |
| Lettuce | Mar 13 | Apr 3 | Apr 17 | May 22 – Jul 31 | 30–60 |
| Lima Beans | — | Apr 24 | — | Jun 26 – Aug 7 | 60–90 |
| Mache | Mar 13 | Apr 3 | Apr 17 | May 29 – Jul 3 | 40–60 |
| Melon | Mar 13 | Apr 24 | May 1 | Jul 10 – Aug 28 | 70–100 |
| Microgreens | Mar 13 | Apr 3 | Apr 17 | Apr 24 – May 22 | 7–21 |
| Mitsuba | Mar 13 | Apr 3 | Apr 10 | Jun 5 – Jul 31 | 50–70 |
| Mizuna | Mar 13 | Apr 3 | Apr 17 | May 22 – Jun 19 | 30–45 |
| Mustard Greens | Mar 13 | Apr 3 | Apr 17 | May 22 – Jul 24 | 30–50 |
| Napa Cabbage | Mar 13 | Apr 3 | Apr 17 | Jun 12 – Jul 17 | 55–75 |
| New Zealand Spinach | Feb 20 | Apr 24 | May 1 | Jun 26 – Jul 24 | 55–70 |
| Okra | Feb 20 | Apr 24 | May 1 | Jun 26 – Aug 21 | 50–65 |
| Onion | Mar 13 | Apr 3 | Apr 17 | Jul 17 – Sep 4 | 90–120 |
| Pac Choi | Mar 13 | Apr 3 | Apr 17 | May 29 – Jun 26 | 40–55 |
| Parsnip | — | Apr 3 | — | Jul 17 – Aug 28 | 100–130 |
| Patty Pan Squash | Mar 13 | Apr 24 | May 1 | Jun 19 – Jul 17 | 45–60 |
| Peas | Mar 13 | Apr 3 | Apr 17 | Jun 12 – Aug 7 | 55–70 |
| Peppers | Feb 6 | Apr 24 | May 1 | Jul 3 – Sep 11 | 60–90 |
| Pole Beans | Feb 20 | Apr 24 | May 1 | Jun 26 – Aug 21 | 55–70 |
| Potatoes | Feb 20 | Apr 24 | May 1 | Jul 10 – Sep 18 | 70–120 |
| Pumpkin | Mar 13 | Apr 24 | May 1 | Jul 31 – Sep 18 | 85–120 |
| Purslane | Mar 13 | Apr 3 | Apr 17 | May 29 – Jul 3 | 40–60 |
| Radicchio | Mar 13 | Apr 3 | Apr 17 | Jun 19 – Jul 24 | 60–80 |
| Radish | — | Apr 3 | — | May 1 – May 22 | 22–35 |
| Rhubarb | — | — | May 8 | — | 365–730 |
| Romanesco | Mar 13 | Apr 3 | Apr 17 | Jul 3 – Aug 14 | 75–100 |
| Rutabaga | — | Apr 3 | — | Jun 26 – Jul 31 | 80–100 |
| Salsify | — | Apr 3 | — | Jul 17 – Aug 28 | 100–130 |
| Savoy Cabbage | Mar 13 | Apr 3 | Apr 17 | Jun 26 – Aug 21 | 70–110 |
| Scallions | Mar 13 | Apr 3 | Apr 17 | Jun 12 – Jul 10 | 50–70 |
| Scarlet Runner Beans | Feb 20 | Apr 24 | May 1 | Jul 3 – Aug 7 | 60–80 |
| Shallot | Mar 13 | Apr 3 | Apr 17 | Jul 17 – Sep 4 | 90–120 |
| Shiso | Feb 27 | Apr 24 | May 1 | Jun 26 – Aug 21 | 50–70 |
| Snap Peas | Feb 20 | Apr 24 | May 1 | Jun 26 – Aug 21 | 55–70 |
| Snow Peas | Mar 13 | Apr 3 | Apr 17 | Jun 12 – Aug 7 | 50–65 |
| Soybeans | — | Apr 24 | — | Jul 17 – Sep 11 | 80–120 |
| Spaghetti Squash | Mar 13 | Apr 24 | May 1 | Jul 31 – Aug 28 | 85–100 |
| Spinach | Mar 13 | Apr 3 | Apr 17 | May 22 – Jul 24 | 35–50 |
| Squash (Summer) | Mar 13 | Apr 24 | May 1 | Jun 19 – Aug 21 | 45–65 |
| Squash (Winter) | Mar 13 | Apr 24 | May 1 | Jul 24 – Sep 18 | 80–120 |
| Sunchoke | — | — | May 1 | Aug 21 – Oct 16 | 110–150 |
| Sunflower | Feb 20 | Apr 24 | May 1 | Jul 10 – Aug 28 | 70–100 |
| Sweet Corn | — | Apr 24 | — | Jun 26 – Aug 7 | 60–90 |
| Sweet Potatoes | Feb 20 | Apr 24 | May 1 | Jul 31 – Sep 18 | 90–120 |
| Tatsoi | Mar 13 | Apr 3 | Apr 17 | May 22 – Jun 26 | 35–50 |
| Tomatillo | Feb 20 | Apr 24 | May 1 | Jul 3 – Sep 11 | 60–85 |
| Tomatoes | Feb 20 | Apr 24 | May 1 | Jul 3 – Sep 11 | 60–85 |
| Turnip | — | Apr 3 | — | May 15 – Jun 19 | 40–60 |
| Watercress | Mar 13 | Apr 3 | Apr 17 | May 29 – Jul 3 | 40–60 |
| Watermelon | Mar 13 | Apr 24 | May 1 | Jul 10 – Aug 28 | 70–100 |
| Wax Beans | — | Apr 24 | — | Jun 19 – Aug 14 | 50–65 |
| Winter Melon | Feb 20 | Apr 24 | May 1 | Jul 31 – Sep 18 | 90–120 |
| Yard Long Beans | Feb 20 | Apr 24 | May 1 | Jun 26 – Aug 7 | 55–80 |
| Zucchini | Mar 13 | Apr 24 | May 1 | Jun 19 – Aug 14 | 45–60 |
🍓 Fruits to Grow in Knox County
27 fruits that grow well in Zone 5a with planting dates for Knox County.
Show all 27 fruits with planting dates
| Plant | Start Indoors | Direct Sow | Transplant | Harvest | Days to Maturity |
|---|---|---|---|---|---|
| Alpine Strawberries | — | — | May 8 | Aug 7 – Oct 23 | 90–180 |
| Aronia | — | — | May 8 | — | 730–1095 |
| Blackberries | — | — | May 8 | — | 365–730 |
| Blueberries | — | — | May 8 | — | 730–1095 |
| Boysenberries | — | — | May 8 | — | 365–730 |
| Cantaloupe | — | — | May 8 | Jul 17 – Aug 21 | 70–90 |
| Che Fruit | — | — | May 8 | — | 1095–1825 |
| Cranberries | — | — | May 8 | — | 730–1095 |
| Currants | — | — | May 8 | — | 730–1095 |
| Elderberries | — | — | May 8 | — | 730–1095 |
| Goji Berries | — | — | May 8 | — | 730–1095 |
| Gooseberries | — | — | May 8 | — | 730–1095 |
| Grapes | — | — | May 8 | — | 730–1095 |
| Ground Cherry | — | — | May 8 | Jul 17 – Sep 11 | 65–80 |
| Hardy Kiwi | — | — | May 8 | — | 1095–1825 |
| Haskaps | — | — | May 8 | — | 730–1095 |
| Honeydew | — | — | May 8 | Jul 31 – Sep 11 | 80–110 |
| Jostaberry | — | — | May 8 | — | 730–1095 |
| Lingonberries | — | — | May 8 | — | 730–1095 |
| Medlar | — | — | May 8 | — | 1095–1825 |
| Mulberries | — | — | May 8 | — | 730–1825 |
| Pawpaw | — | — | May 8 | — | 1095–2555 |
| Persimmon | — | — | May 8 | — | 1095–2555 |
| Quince | — | — | May 8 | — | 1095–1825 |
| Raspberries | — | — | May 8 | — | 365–730 |
| Serviceberries | — | — | May 8 | — | 730–1095 |
| Strawberries | — | — | May 8 | Aug 7 – Oct 23 | 90–365 |
🌿 Herbs to Grow in Knox County
37 herbs that grow well in Zone 5a with planting dates for Knox County.
Show all 37 herbs with planting dates
| Plant | Start Indoors | Direct Sow | Transplant | Harvest | Days to Maturity |
|---|---|---|---|---|---|
| Angelica | Mar 13 | Apr 3 | Apr 10 | — | 365–730 |
| Anise | Mar 13 | Apr 3 | Apr 10 | Jul 10 – Sep 25 | 90–120 |
| Basil | Feb 27 | Apr 24 | May 1 | Jun 26 – Aug 28 | 50–75 |
| Bee Balm | — | — | Apr 24 | Jul 24 – Oct 9 | 90–120 |
| Borage | Mar 13 | Apr 3 | Apr 10 | Jun 5 – Jul 24 | 50–60 |
| Caraway | Mar 13 | Apr 3 | Apr 10 | — | 365–450 |
| Catnip | — | — | Apr 24 | Jun 26 – Aug 28 | 60–80 |
| Chamomile | Mar 13 | Apr 3 | Apr 10 | Jun 12 – Aug 21 | 60–90 |
| Chervil | Mar 13 | Apr 3 | Apr 10 | May 22 – Jul 24 | 40–60 |
| Chives | — | — | Apr 24 | Jun 26 – Sep 4 | 60–90 |
| Cilantro | Mar 13 | Apr 3 | Apr 10 | May 22 – Jul 24 | 40–60 |
| Comfrey | — | — | Apr 24 | Jun 26 – Sep 4 | 60–90 |
| Cumin | Mar 13 | Apr 3 | Apr 10 | Jul 24 – Sep 25 | 100–120 |
| Dill | Mar 13 | Apr 3 | Apr 10 | May 22 – Jul 24 | 40–60 |
| Echinacea | — | — | Apr 24 | Aug 28 – Oct 9 | 120–180 |
| Epazote | Feb 27 | Apr 24 | May 1 | Jun 19 – Aug 14 | 45–60 |
| Fennel (herb) | Mar 13 | Apr 3 | Apr 10 | Jun 12 – Aug 21 | 60–90 |
| Feverfew | — | — | Apr 24 | Jul 24 – Oct 9 | 90–120 |
| Garlic Chives | — | — | Apr 24 | Jun 26 – Sep 4 | 60–90 |
| Horehound | — | — | Apr 24 | Jul 10 – Sep 4 | 75–90 |
| Hyssop | — | — | Apr 24 | Jul 3 – Sep 4 | 70–90 |
| Lavender | — | — | Apr 24 | Jul 24 – Oct 9 | 90–200 |
| Lemon Balm | — | — | Apr 24 | Jun 26 – Aug 14 | 60–70 |
| Lemon Thyme | — | — | Apr 24 | Jul 3 – Sep 4 | 70–90 |
| Lovage | — | — | Apr 24 | Jul 3 – Sep 4 | 70–90 |
| Mint | — | — | Apr 24 | Jun 26 – Sep 4 | 60–90 |
| Oregano | — | — | Apr 24 | Jun 26 – Sep 4 | 60–90 |
| Parsley | Mar 13 | Apr 3 | Apr 10 | Jun 12 – Aug 14 | 60–80 |
| Rue | — | — | Apr 24 | Jul 3 – Sep 4 | 70–90 |
| Sage | — | — | Apr 24 | Jul 10 – Sep 4 | 75–90 |
| Savory | — | — | Apr 24 | Jun 19 – Aug 14 | 50–70 |
| Sorrel | Mar 13 | Apr 3 | Apr 10 | May 22 – Jul 24 | 40–60 |
| Tarragon | — | — | Apr 24 | Jun 26 – Sep 4 | 60–90 |
| Thai Basil | Feb 27 | Apr 24 | May 1 | Jun 26 – Aug 28 | 50–75 |
| Thyme | — | — | Apr 24 | Jul 3 – Sep 4 | 70–90 |
| Valerian | — | — | Apr 24 | Aug 28 – Oct 9 | 120–180 |
| Yarrow | — | — | Apr 24 | Jul 24 – Oct 9 | 90–120 |
Monthly Planting Guide for Knox County
Gardening Guides & Resources
Helpful guides from The Ultimate Homestead to improve your garden in Knox County.
Frequently Asked Questions
What planting zone is Knox County, IL?
Knox 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 Knox County, IL?
Based on 31 years of NOAA weather station data, the median last spring frost in Knox County falls around April 17. In 8 out of 10 years, last frost lands between April 4 and May 3 — a 28-day window of variability. Use May 3 as your conservative safe-to-plant date for frost-sensitive crops.
When is the first fall frost in Knox County, IL?
The median first fall frost in Knox County arrives around October 15. In cold years it can arrive as early as October 2; in mild years as late as November 4. Harvest or protect frost-sensitive crops — tomatoes, peppers, basil, squash — before this date.
How long is the growing season in Knox County?
Knox County has a frost-free growing season of approximately 181 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 2.83 days per decade.
What is the soil like in Knox County for gardening?
Knox County has predominantly Silt Loam soil with a pH range of 6–6.8 and Well Drained drainage. Most vegetables and herbs grow well with standard composting and seasonal soil amendment.
What is grown commercially in Knox County?
Knox County has commercial agriculture that includes Corn, Soybeans, Hay, Wheat, Oats. These crops reflect the local climate and soil conditions — what succeeds commercially often translates well to home gardens in the same area.
Is Knox County a good location for home gardening?
Knox County scores 56/100 (Moderate) 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 Knox County gardeners in Zone 5a organize planting dates, track what's growing, and never miss a planting window.
Get Your Free Garden Planner →Free download. Plan your entire garden season in minutes.
