Jefferson County, ID — Planting Guide
Jefferson County is in USDA Zone 5a. The average last spring frost is May 22 and the first fall frost is September 21, giving you a growing season of approximately 122 days.
At an elevation of 5,094 ft, Jefferson County receives approximately 18 in of rainfall annually. Summer highs average 87°F with winter lows around 18°F. The predominant soil type is Loam.
Based on 31 years of NOAA climate station data, the last frost date here varies by 47 days year to year — ranging from May 1 in warm years to June 17 in cold years. The growing season is trending longer by about 6.15 days per decade. Jefferson County scores 34/100 (Challenging) on the Microclimate Index.
🌡️ Zone
5a (-20°F to -15°F min)
❄️ Last Frost
May 22
🍂 First Frost
September 21
📅 Growing Season
122 days
⛰️ Elevation
5,094 ft
🌧️ Annual Rainfall
18 in
Monthly Watering Calendar for Jefferson County
When you'll need to water your garden — based on average monthly rainfall vs. the ~1 inch/week most gardens need.
Quick context: The 1-inch-per-week rule applies to most vegetable crops. Jefferson County averages 18" 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 | 1.1 in | 6 days | — | None |
| Feb | 1.2 in | 5 days | — | None |
| Mar | 1.4 in | 7 days | — | None |
| Apr | 2 in | 8 days | 2.3 in | High |
| May | 1.9 in | 7 days | 2.4 in | High |
| Jun | 1.4 in | 4 days | 2.9 in | High |
| Jul | 1.4 in | 5 days | 2.9 in | High |
| Aug | 2 in | 6 days | 2.3 in | High |
| Sep | 1.6 in | 5 days | 2.7 in | High |
| Oct | 1.6 in | 5 days | 2.7 in | High |
| Nov | 1.3 in | 5 days | — | None |
| Dec | 1 in | 6 days | — | None |
Annual total: 17.9 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.
Jefferson County Soil Profile
Soil Type
Loam
Soil pH
6.3-7.8
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) | Jun 17 | Oct 13 | 118 days |
| Cautious | Jun 4 | Oct 2 | 120 days |
| Average year | May 22 | Sep 21 | 122 days |
| Optimistic | May 9 | Sep 9 | 123 days |
| Aggressive (risky) | May 1 | Sep 4 | 126 days |
Not very — frost dates can vary by ±47 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 longer here (about 6.2 days per decade). Spring is arriving earlier than it used to. Good news for gardeners.
Gardening Difficulty Score
Jefferson County has challenging growing conditions. Season extension and careful variety selection are essential.
Local Gardening Help in Jefferson 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 Jefferson County's climate and soil.
County Extension Office
Jefferson County University of Idaho Extension Extension Office
Phone: 208-885-6681
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 Jefferson County
Finding local nurseries & garden centers in Jefferson County
Why Buy Local
Local nurseries carry plants that are proven to grow in your area. Staff can give you advice specific to Jefferson 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 Jefferson County ID" or "garden center Jefferson 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 Jefferson County ID" or check your extension office and local parks department. Facebook groups like "Jefferson County Gardeners" or "Idaho 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 5 more succession options
Sunlight & Day Length in Jefferson County
Monthly daylight hours and peak sun — critical for onion varieties, photoperiod-sensitive plants, and solar garden planning.
For new gardeners: The longest day at Jefferson County's latitude gets longer the further north you go. Strawberries, garlic, onions all care. The shortest day gets shorter — which limits winter growing for greens without artificial light.
Longest Day
15.3 hours
Summer solstice daylight
Shortest Day
8.7 hours
Winter solstice daylight
Peak Sun Hours
10.7 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 | 9.1 hr | 4.8 hr | Short day |
| February | 10.3 hr | 5.8 hr | Short day |
| March | 11.6 hr | 7.2 hr | Short day |
| April | 13.2 hr | 7.5 hr | Neutral |
| May | 14.5 hr | 8.7 hr | Long day |
| June | 15.3 hr | 10.6 hr | Long day |
| July | 15 hr | 10.7 hr | Long day |
| August | 13.8 hr | 9.4 hr | Neutral |
| September | 12.3 hr | 8.4 hr | Neutral |
| October | 10.8 hr | 7 hr | Short day |
| November | 9.4 hr | 5.6 hr | Short day |
| December | 8.7 hr | 4.7 hr | Short day |
Peak sun hours factor in typical cloud cover — use these for solar panel and shade-planning calculations.
Soil Temperature & Composting in Jefferson County
Monthly soil temps tell you when to plant warm-season crops, and when your compost pile is actively working.
The practical takeaway: Air temperature lies. Your air can be 70°F in April but the soil 4 inches down is still 50°F — too cold for tomatoes or peppers to root properly. Jefferson County's soil temperature curve tells you the real planting window. A $5 soil thermometer pays for itself in one season.
Plant Warm Crops When
Soil reaches 60°F+
Soil warm enough from Jul through Aug.
Best Month to Compost
Jun
Microbial activity peaks when soil is warm.
Active Composting
4 months
Short season — insulate pile or use indoor vermicomposting.
View detailed monthly data
| Month | Soil 4" Deep | Soil 8" Deep | Compost Activity | Time to Finish |
|---|---|---|---|---|
| Jan | 7°F | 16°F | ❄️ Dormant | ~36 weeks |
| Feb | 10°F | 15°F | ❄️ Dormant | ~36 weeks |
| Mar | 16°F | 19°F | ❄️ Dormant | ~36 weeks |
| Apr | 32°F | 30°F | ❄️ Dormant | ~36 weeks |
| May | 43°F | 40°F | 🐢 Slow | ~24 weeks |
| Jun | 56°F | 49°F | ♻️ Active | ~14 weeks |
| Jul | 61°F | 55°F | ♻️ Active | ~14 weeks |
| Aug | 64°F | 57°F | ♻️ Active | ~14 weeks |
| Sep | 57°F | 54°F | ♻️ Active | ~14 weeks |
| Oct | 43°F | 45°F | 🐢 Slow | ~24 weeks |
| Nov | 28°F | 34°F | ❄️ Dormant | ~36 weeks |
| Dec | 15°F | 23°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 Jefferson County
Computed from local climate patterns — warmer, humid conditions increase pest generations and fungal disease risk.
For new gardeners: Pest pressure scales with warmth and humidity. Hot humid Jefferson County sees year-round bugs and fungal disease; cold dry regions see almost none. A high pest score means crop rotation, resistant varieties, and a weekly pest-watch routine from day one.
Insect Pest Pressure
Moderate — common pests appear but manageable with monitoring.
Disease Risk
Low disease risk — dry conditions reduce fungal problems.
Seasonal Risk
View 6 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 | Low | Jul, Aug |
| Cabbage loopers | Moderate | May, Jun, Jul, Aug |
| Slugs | Low | Apr, May, Jun |
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 Jefferson County
Cover crops protect bare soil, fix nitrogen, suppress weeds, and improve soil structure — with planting dates calibrated for your area.
The practical takeaway: Why not just leave bare soil? Weed seeds, erosion, nutrient leaching, and crust formation. A cover crop solves all of these for the cost of seeds and one mowing.
Spring Cover Crops (3 options) — Build soil before the main growing season
| Crop | Plant By | Terminate | N-Fixing | Soil Benefit |
|---|---|---|---|---|
| Buckwheat | May 30 | Jul 27 | — | Rapid growth, attracts pollinators, suppresses weeds |
| Sorghum-sudan grass | May 29 | Jul 13 | — | Massive biomass, breaks compaction, suppresses nematodes |
| White clover | Apr 25 | Jul 13 | ✓ 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 5 | Aug 31 | — | 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 15 | May 8 | ✓ Yes | Fixes nitrogen, good for heavy clay soils |
| Daikon radish | Aug 1 | May 1 | — | Deep taproot breaks compaction, excellent for clay soils |
| Hairy vetch | Jul 5 | May 1 | ✓ Yes | Excellent nitrogen fixer, good for depleted soils |
| Oats | Aug 8 | May 8 | — | Quick biomass, winterkills in cold zones — no spring tillage needed |
| Winter rye | Jun 27 | May 1 | — | Suppresses weeds, prevents erosion, breaks up compacted soil |
| Winter wheat | Jun 29 | May 8 | — | Erosion control, weed suppression, good biomass |
Wind & Microclimate in Jefferson County
Quick context: New gardeners under-plan for wind. Jefferson County averages 10.5 mph — fine for most days. But every region has its windy days, and the first time a row of unstaked peppers leans over after a storm is a lesson you only need once.
Wind dries soil, stresses plants, and affects frost patterns. Understanding your exposure helps with garden placement.
Seasonal Wind Speed
Spring: 14 mph Summer: 11 mph
Fall: 13 mph Winter: 15 mph
Prevailing wind: W. Windy area — plant a windbreak hedge on the W side of your garden.
Windbreak Benefit
6.7/10
Moderately beneficial — a simple fence or trellis can protect delicate crops from wind stress.
Frost Pocket Risk
High
Hilly terrain with 1,095 ft of elevation range — cold air pools in low spots. Avoid planting frost-sensitive crops in valleys.
Rainwater Harvesting in Jefferson County
How much water you can collect, when to collect it, and what size system you need for your garden.
Why it matters: Building a rainwater system is mostly about doing the math: roof area × annual rainfall × 0.6 = gallons you could realistically capture. For Jefferson County, that's your 18" times your roof.
Annual Collection
8,921 gal
Per 1,000 sq ft of roof area (at 80% collection efficiency)
Recommended Setup
8 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
Apr, May, Aug, Sep
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 17.9 inches of rain per year
- A 1,000 sq ft roof can collect roughly 8,921 gallons annually
- Rainwater harvesting is fully legal in your state
- In your dry climate, every drop counts — consider a larger cistern system
- Position collection tanks in shade to reduce evaporation and algae growth
Soil & Growing Conditions in Jefferson County
Soil Type
Loam
Soil pH 6.3–7.8 · Well Drained drainage
Good candidate for raised beds to maximise drainage and extend the season.
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
122-day frost-free season
A short season means indoor starts are critical for warm-season crops. Prioritise cold-hardy, fast-maturing varieties and use row covers to extend autumn harvests.
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.
🥬 Vegetables to Grow in Jefferson County
105 vegetables that grow well in Zone 5a with planting dates for Jefferson County.
Show all 105 vegetables with planting dates
| Plant | Start Indoors | Direct Sow | Transplant | Fall Plant | Harvest | Days to Maturity |
|---|---|---|---|---|---|---|
| Acorn Squash | Apr 17 | May 29 | Jun 5 | — | Aug 28 – Oct 2 | 80–100 |
| Amaranth | Mar 27 | May 29 | Jun 5 | — | Sep 4 – Oct 23 | 90–120 |
| Arugula | Apr 17 | May 8 | May 22 | Jul 13 | Jun 26 – Aug 28 | 30–50 |
| Asparagus | — | — | Jun 5 | — | — | 730–1095 |
| Beets | — | May 8 | — | Jul 13 | Jul 3 – Jul 31 | 50–70 |
| Belgian Endive | Apr 17 | May 8 | May 22 | Jul 13 | Sep 11 – Nov 6 | 110–150 |
| Bitter Melon | Mar 27 | May 29 | Jun 5 | — | Aug 7 – Sep 18 | 60–90 |
| Black Beans | — | May 29 | — | — | Aug 28 – Oct 16 | 90–120 |
| Bok Choy | Apr 17 | May 8 | May 22 | Jul 13 | Jul 3 – Aug 7 | 40–60 |
| Broccoli | Apr 17 | May 8 | May 22 | Jul 13 | Jul 24 – Sep 4 | 60–90 |
| Broccoli Rabe | Apr 17 | May 8 | May 22 | Jul 13 | Jul 3 – Aug 7 | 40–60 |
| Brussels Sprouts | Apr 17 | May 8 | May 22 | Jul 13 | Aug 21 – Oct 16 | 90–130 |
| Butternut Squash | Apr 17 | May 29 | Jun 5 | — | Sep 4 – Oct 9 | 85–110 |
| Cabbage | Apr 17 | May 8 | May 22 | Jul 13 | Jul 24 – Sep 18 | 60–100 |
| Calabash | Mar 27 | May 29 | Jun 5 | — | Aug 28 – Oct 23 | 80–120 |
| Carrots | — | May 8 | — | Jul 13 | Jul 10 – Aug 14 | 60–80 |
| Cauliflower | Apr 17 | May 8 | May 22 | Jul 13 | Jul 17 – Sep 18 | 55–100 |
| Celeriac | Apr 17 | May 8 | May 22 | Jul 13 | Sep 4 – Oct 9 | 100–120 |
| Celery | Apr 17 | May 8 | May 22 | Jul 13 | Aug 14 – Oct 9 | 80–120 |
| Celtuce | Apr 17 | May 8 | May 22 | Jul 13 | Jul 24 – Sep 4 | 60–90 |
| Chard | Apr 17 | May 8 | May 22 | Jul 13 | Jul 17 – Sep 4 | 50–60 |
| Chickpeas | Apr 17 | May 8 | May 22 | Jul 13 | Aug 14 – Sep 25 | 80–110 |
| Chicory | Apr 17 | May 8 | May 22 | Jul 13 | Jul 24 – Sep 4 | 60–85 |
| Chinese Cabbage | Apr 17 | May 8 | May 22 | Jul 13 | Jul 17 – Aug 14 | 50–70 |
| Christmas Lima Beans | Mar 27 | May 29 | Jun 5 | — | Aug 28 – Oct 2 | 80–100 |
| Collard Greens | Apr 17 | May 8 | May 22 | Jul 13 | Jul 17 – Sep 18 | 55–75 |
| Corn | — | May 29 | — | — | Jul 31 – Sep 25 | 60–100 |
| Cowpeas | — | May 29 | — | — | Jul 31 – Sep 11 | 60–90 |
| Cress | Apr 17 | May 8 | May 22 | Jul 13 | Jun 5 – Jun 26 | 14–21 |
| Crookneck Squash | Apr 17 | May 29 | Jun 5 | — | Jul 24 – Aug 21 | 45–60 |
| Crosne | — | May 8 | — | Jul 13 | Oct 9 – Oct 23 | 150–200 |
| Cucumber | Apr 17 | May 29 | Jun 5 | — | Jul 31 – Sep 25 | 50–70 |
| Daikon | — | May 8 | — | Jul 13 | Jul 3 – Jul 31 | 50–70 |
| Delicata Squash | Apr 17 | May 29 | Jun 5 | — | Aug 28 – Oct 2 | 80–100 |
| Edamame | — | May 29 | — | — | Aug 14 – Sep 25 | 75–100 |
| Eggplant | Mar 13 | May 29 | Jun 5 | — | Aug 14 – Oct 16 | 65–85 |
| Endive | Apr 17 | May 8 | May 22 | Jul 13 | Jul 10 – Aug 14 | 45–65 |
| Escarole | Apr 17 | May 8 | May 22 | Jul 13 | Jul 17 – Aug 14 | 50–70 |
| Fava Beans | Apr 17 | May 8 | May 22 | Jul 13 | Aug 7 – Sep 18 | 75–100 |
| Fennel | Mar 27 | May 29 | Jun 5 | — | Aug 7 – Sep 18 | 60–90 |
| Garlic | — | — | — | Aug 10 | Nov 9 – Jan 25 | 90–240 |
| Green Beans | — | May 29 | — | — | Jul 24 – Sep 18 | 50–65 |
| Horseradish | — | — | Jun 5 | — | Oct 9 – Nov 20 | 120–180 |
| Hot Peppers | Mar 13 | May 29 | Jun 5 | — | Aug 14 – Nov 20 | 70–120 |
| Hubbard Squash | Apr 17 | May 29 | Jun 5 | — | Sep 18 – Oct 23 | 100–120 |
| Kabocha | Apr 17 | May 29 | Jun 5 | — | Sep 4 – Oct 2 | 85–100 |
| Kai Lan | Apr 17 | May 8 | May 22 | Jul 13 | Jul 10 – Aug 7 | 45–60 |
| Kale | Apr 17 | May 8 | May 22 | Jul 13 | Jul 17 – Sep 11 | 50–70 |
| Kidney Beans | — | May 29 | — | — | Aug 28 – Oct 2 | 85–110 |
| Kohlrabi | Apr 17 | May 8 | May 22 | Jul 13 | Jul 10 – Aug 14 | 45–65 |
| Komatsuna | Apr 17 | May 8 | May 22 | Jul 13 | Jun 26 – Jul 31 | 35–50 |
| Leeks | Apr 17 | May 8 | May 22 | Jul 13 | Aug 21 – Nov 6 | 90–150 |
| Lentils | Apr 17 | May 8 | May 22 | Jul 13 | Aug 14 – Sep 25 | 80–110 |
| Lettuce | Apr 17 | May 8 | May 22 | Jul 13 | Jun 26 – Sep 4 | 30–60 |
| Lima Beans | — | May 29 | — | — | Jul 31 – Sep 11 | 60–90 |
| Mache | Apr 17 | May 8 | May 22 | Jul 13 | Jul 3 – Aug 7 | 40–60 |
| Melon | Apr 17 | May 29 | Jun 5 | — | Aug 14 – Oct 2 | 70–100 |
| Microgreens | Apr 17 | May 8 | May 22 | Jul 13 | May 29 – Jun 26 | 7–21 |
| Mitsuba | Apr 17 | May 8 | May 15 | Jul 13 | Jul 10 – Sep 4 | 50–70 |
| Mizuna | Apr 17 | May 8 | May 22 | Jul 13 | Jun 26 – Jul 24 | 30–45 |
| Mustard Greens | Apr 17 | May 8 | May 22 | Jul 13 | Jun 26 – Aug 28 | 30–50 |
| Napa Cabbage | Apr 17 | May 8 | May 22 | Jul 13 | Jul 17 – Aug 21 | 55–75 |
| New Zealand Spinach | Mar 27 | May 29 | Jun 5 | — | Jul 31 – Aug 28 | 55–70 |
| Okra | Mar 27 | May 29 | Jun 5 | — | Jul 31 – Sep 25 | 50–65 |
| Onion | Apr 17 | May 8 | May 22 | Jul 13 | Aug 21 – Oct 9 | 90–120 |
| Pac Choi | Apr 17 | May 8 | May 22 | Jul 13 | Jul 3 – Jul 31 | 40–55 |
| Parsnip | — | May 8 | — | Jul 13 | Aug 21 – Oct 2 | 100–130 |
| Patty Pan Squash | Apr 17 | May 29 | Jun 5 | — | Jul 24 – Aug 21 | 45–60 |
| Peas | Apr 17 | May 8 | May 22 | Jul 13 | Jul 17 – Sep 11 | 55–70 |
| Peppers | Mar 13 | May 29 | Jun 5 | — | Aug 7 – Oct 16 | 60–90 |
| Pole Beans | Mar 27 | May 29 | Jun 5 | — | Jul 31 – Sep 25 | 55–70 |
| Potatoes | Mar 27 | May 29 | Jun 5 | — | Aug 14 – Oct 23 | 70–120 |
| Pumpkin | Apr 17 | May 29 | Jun 5 | — | Sep 4 – Oct 23 | 85–120 |
| Purslane | Apr 17 | May 8 | May 22 | Jul 13 | Jul 3 – Aug 7 | 40–60 |
| Radicchio | Apr 17 | May 8 | May 22 | Jul 13 | Jul 24 – Aug 28 | 60–80 |
| Radish | — | May 8 | — | Jul 13 | Jun 5 – Jun 26 | 22–35 |
| Rhubarb | — | — | Jun 12 | — | — | 365–730 |
| Romanesco | Apr 17 | May 8 | May 22 | Jul 13 | Aug 7 – Sep 18 | 75–100 |
| Rutabaga | — | May 8 | — | Jul 13 | Jul 31 – Sep 4 | 80–100 |
| Salsify | — | May 8 | — | Jul 13 | Aug 21 – Oct 2 | 100–130 |
| Savoy Cabbage | Apr 17 | May 8 | May 22 | Jul 13 | Jul 31 – Sep 25 | 70–110 |
| Scallions | Apr 17 | May 8 | May 22 | Jul 13 | Jul 17 – Aug 14 | 50–70 |
| Scarlet Runner Beans | Mar 27 | May 29 | Jun 5 | — | Aug 7 – Sep 11 | 60–80 |
| Shallot | Apr 17 | May 8 | May 22 | Jul 13 | Aug 21 – Oct 9 | 90–120 |
| Shiso | Apr 3 | May 29 | Jun 5 | — | Jul 31 – Sep 25 | 50–70 |
| Snap Peas | Mar 27 | May 29 | Jun 5 | — | Jul 31 – Sep 25 | 55–70 |
| Snow Peas | Apr 17 | May 8 | May 22 | Jul 13 | Jul 17 – Sep 11 | 50–65 |
| Soybeans | — | May 29 | — | — | Aug 21 – Oct 16 | 80–120 |
| Spaghetti Squash | Apr 17 | May 29 | Jun 5 | — | Sep 4 – Oct 2 | 85–100 |
| Spinach | Apr 17 | May 8 | May 22 | Jul 13 | Jun 26 – Aug 28 | 35–50 |
| Squash (Summer) | Apr 17 | May 29 | Jun 5 | — | Jul 24 – Sep 25 | 45–65 |
| Squash (Winter) | Apr 17 | May 29 | Jun 5 | — | Aug 28 – Oct 23 | 80–120 |
| Sunchoke | — | — | Jun 5 | — | Sep 25 – Nov 20 | 110–150 |
| Sweet Corn | — | May 29 | — | — | Jul 31 – Sep 11 | 60–90 |
| Sweet Potatoes | Mar 27 | May 29 | Jun 5 | — | Sep 4 – Oct 23 | 90–120 |
| Tatsoi | Apr 17 | May 8 | May 22 | Jul 13 | Jun 26 – Jul 31 | 35–50 |
| Tomatillo | Mar 27 | May 29 | Jun 5 | — | Aug 7 – Oct 16 | 60–85 |
| Tomatoes | Mar 27 | May 29 | Jun 5 | — | Aug 7 – Oct 16 | 60–85 |
| Turnip | — | May 8 | — | Jul 13 | Jun 19 – Jul 24 | 40–60 |
| Watercress | Apr 17 | May 8 | May 22 | Jul 13 | Jul 3 – Aug 7 | 40–60 |
| Watermelon | Apr 17 | May 29 | Jun 5 | — | Aug 14 – Oct 2 | 70–100 |
| Wax Beans | — | May 29 | — | — | Jul 24 – Sep 18 | 50–65 |
| Winter Melon | Mar 27 | May 29 | Jun 5 | — | Sep 4 – Oct 23 | 90–120 |
| Yard Long Beans | Mar 27 | May 29 | Jun 5 | — | Jul 31 – Sep 11 | 55–80 |
| Zucchini | Apr 17 | May 29 | Jun 5 | — | Jul 24 – Sep 18 | 45–60 |
🍓 Fruits to Grow in Jefferson County
27 fruits that grow well in Zone 5a with planting dates for Jefferson County.
Show all 27 fruits with planting dates
| Plant | Start Indoors | Direct Sow | Transplant | Fall Plant | Harvest | Days to Maturity |
|---|---|---|---|---|---|---|
| Alpine Strawberries | — | — | Jun 12 | — | Sep 11 – Nov 27 | 90–180 |
| Aronia | — | — | Jun 12 | — | — | 730–1095 |
| Blackberries | — | — | Jun 12 | — | — | 365–730 |
| Blueberries | — | — | Jun 12 | — | — | 730–1095 |
| Boysenberries | — | — | Jun 12 | — | — | 365–730 |
| Cantaloupe | — | — | Jun 12 | — | Aug 21 – Sep 25 | 70–90 |
| Che Fruit | — | — | Jun 12 | — | — | 1095–1825 |
| Cranberries | — | — | Jun 12 | — | — | 730–1095 |
| Currants | — | — | Jun 12 | — | — | 730–1095 |
| Elderberries | — | — | Jun 12 | — | — | 730–1095 |
| Goji Berries | — | — | Jun 12 | — | — | 730–1095 |
| Gooseberries | — | — | Jun 12 | — | — | 730–1095 |
| Grapes | — | — | Jun 12 | — | — | 730–1095 |
| Ground Cherry | — | — | Jun 12 | — | Aug 21 – Oct 16 | 65–80 |
| Hardy Kiwi | — | — | Jun 12 | — | — | 1095–1825 |
| Haskaps | — | — | Jun 12 | — | — | 730–1095 |
| Honeydew | — | — | Jun 12 | — | Sep 4 – Oct 16 | 80–110 |
| Jostaberry | — | — | Jun 12 | — | — | 730–1095 |
| Lingonberries | — | — | Jun 12 | — | — | 730–1095 |
| Medlar | — | — | Jun 12 | — | — | 1095–1825 |
| Mulberries | — | — | Jun 12 | — | — | 730–1825 |
| Pawpaw | — | — | Jun 12 | — | — | 1095–2555 |
| Persimmon | — | — | Jun 12 | — | — | 1095–2555 |
| Quince | — | — | Jun 12 | — | — | 1095–1825 |
| Raspberries | — | — | Jun 12 | — | — | 365–730 |
| Serviceberries | — | — | Jun 12 | — | — | 730–1095 |
| Strawberries | — | — | Jun 12 | — | Sep 11 – Nov 27 | 90–365 |
🌿 Herbs to Grow in Jefferson County
34 herbs that grow well in Zone 5a with planting dates for Jefferson County.
Show all 34 herbs with planting dates
| Plant | Start Indoors | Direct Sow | Transplant | Fall Plant | Harvest | Days to Maturity |
|---|---|---|---|---|---|---|
| Angelica | Apr 17 | May 8 | May 15 | Jul 13 | — | 365–730 |
| Anise | Apr 17 | May 8 | May 15 | Jul 13 | Aug 14 – Oct 30 | 90–120 |
| Basil | Apr 3 | May 29 | Jun 5 | — | Jul 31 – Oct 2 | 50–75 |
| Bee Balm | — | — | May 29 | — | Aug 28 – Nov 13 | 90–120 |
| Borage | Apr 17 | May 8 | May 15 | Jul 13 | Jul 10 – Aug 28 | 50–60 |
| Caraway | Apr 17 | May 8 | May 15 | Jul 13 | — | 365–450 |
| Catnip | — | — | May 29 | — | Jul 31 – Oct 2 | 60–80 |
| Chamomile | Apr 17 | May 8 | May 15 | Jul 13 | Jul 17 – Sep 25 | 60–90 |
| Chervil | Apr 17 | May 8 | May 15 | Jul 13 | Jun 26 – Aug 28 | 40–60 |
| Chives | — | — | May 29 | — | Jul 31 – Oct 9 | 60–90 |
| Cilantro | Apr 17 | May 8 | May 15 | Jul 13 | Jun 26 – Aug 28 | 40–60 |
| Comfrey | — | — | May 29 | — | Jul 31 – Oct 9 | 60–90 |
| Cumin | Apr 17 | May 8 | May 15 | Jul 13 | Aug 28 – Oct 30 | 100–120 |
| Dill | Apr 17 | May 8 | May 15 | Jul 13 | Jun 26 – Aug 28 | 40–60 |
| Epazote | Apr 3 | May 29 | Jun 5 | — | Jul 24 – Sep 18 | 45–60 |
| Fennel (herb) | Apr 17 | May 8 | May 15 | Jul 13 | Jul 17 – Sep 25 | 60–90 |
| Feverfew | — | — | May 29 | — | Aug 28 – Nov 13 | 90–120 |
| Garlic Chives | — | — | May 29 | — | Jul 31 – Oct 9 | 60–90 |
| Horehound | — | — | May 29 | — | Aug 14 – Oct 9 | 75–90 |
| Hyssop | — | — | May 29 | — | Aug 7 – Oct 9 | 70–90 |
| Lemon Balm | — | — | May 29 | — | Jul 31 – Sep 18 | 60–70 |
| Lemon Thyme | — | — | May 29 | — | Aug 7 – Oct 9 | 70–90 |
| Lovage | — | — | May 29 | — | Aug 7 – Oct 9 | 70–90 |
| Mint | — | — | May 29 | — | Jul 31 – Oct 9 | 60–90 |
| Oregano | — | — | May 29 | — | Jul 31 – Oct 9 | 60–90 |
| Parsley | Apr 17 | May 8 | May 15 | Jul 13 | Jul 17 – Sep 18 | 60–80 |
| Rue | — | — | May 29 | — | Aug 7 – Oct 9 | 70–90 |
| Sage | — | — | May 29 | — | Aug 14 – Oct 9 | 75–90 |
| Savory | — | — | May 29 | — | Jul 24 – Sep 18 | 50–70 |
| Sorrel | Apr 17 | May 8 | May 15 | Jul 13 | Jun 26 – Aug 28 | 40–60 |
| Tarragon | — | — | May 29 | — | Jul 31 – Oct 9 | 60–90 |
| Thai Basil | Apr 3 | May 29 | Jun 5 | — | Jul 31 – Oct 2 | 50–75 |
| Thyme | — | — | May 29 | — | Aug 7 – Oct 9 | 70–90 |
| Valerian | — | — | May 29 | — | Oct 2 – Nov 13 | 120–180 |
🌸 Flowers to Grow in Jefferson County
51 flowers that grow well in Zone 5a with planting dates for Jefferson County.
Show all 51 flowers with planting dates
| Plant | Start Indoors | Direct Sow | Transplant | Fall Plant | Bloom | Days to Maturity |
|---|---|---|---|---|---|---|
| Ageratum | Apr 3 | May 29 | May 29 | — | Jul 24 – Oct 16 | 60–75 |
| Alliums | — | — | — | Aug 10 | Sep 14 – Oct 12 | 28–42 |
| Anemones | Apr 24 | — | May 22 | — | Jul 3 – Jul 31 | 90–120 |
| Astilbe | Mar 20 | — | Jun 5 | — | Aug 21 – Oct 23 | 70–100 |
| Bachelor's Button | Apr 10 | May 1 | May 22 | — | Jul 24 – Oct 2 | 60–90 |
| Begonias | Mar 13 | — | May 29 | — | Aug 7 – Oct 30 | 70–90 |
| Black-eyed Susan | Mar 20 | May 22 | Jun 5 | — | Aug 21 – Nov 20 | 60–80 |
| Bleeding Hearts | Mar 20 | — | Jun 5 | — | Jul 31 – Sep 11 | 60–90 |
| Calendula | Apr 10 | May 1 | May 22 | — | Jul 10 – Oct 2 | 50–70 |
| Celosia | Apr 17 | Jun 5 | Jun 5 | — | Aug 7 – Nov 6 | 60–90 |
| Columbine | Mar 20 | Jun 5 | Jun 5 | — | Jul 31 – Sep 11 | 70–100 |
| Coreopsis | Mar 20 | May 29 | Jun 5 | — | Aug 14 – Nov 20 | 60–80 |
| Cosmos | Apr 24 | May 29 | May 29 | — | Aug 7 – Oct 30 | 60–90 |
| Crocus | — | — | — | Aug 10 | Jun 22 – Jul 13 | 10–20 |
| Daffodils | — | — | — | Aug 10 | Jun 29 – Jul 20 | 20–40 |
| Dahlias | Apr 24 | May 29 | May 29 | — | Aug 21 – Nov 13 | 70–120 |
| Daylily | Mar 20 | — | Jun 5 | — | Aug 28 – Nov 20 | 60–90 |
| Dianthus | Mar 20 | Apr 24 | May 8 | — | Jun 26 – Sep 11 | 60–80 |
| Echinacea (Purple Coneflower) | Mar 20 | Jun 5 | Jun 5 | — | Aug 28 – Nov 20 | 70–90 |
| Foxglove | Mar 20 | Jun 5 | Jun 5 | — | Jul 31 – Sep 11 | 80–120 |
| Gaillardia (Blanket Flower) | Mar 27 | Jun 5 | Jun 5 | — | Aug 14 – Dec 4 | 70–100 |
| Geraniums | Mar 13 | — | May 29 | — | Aug 7 – Oct 30 | 70–100 |
| Gladiolus | — | May 29 | May 29 | — | Aug 21 – Nov 13 | 70–100 |
| Hostas | Mar 13 | — | Jun 5 | — | Aug 28 – Nov 20 | 60–90 |
| Hyacinths | — | — | — | Aug 10 | Jul 20 – Aug 17 | 14–28 |
| Hydrangeas | Mar 13 | — | Jun 5 | — | Aug 21 – Nov 6 | 90–150 |
| Impatiens | Mar 27 | — | May 29 | — | Aug 7 – Oct 30 | 60–75 |
| Irises | — | Division | Jun 5 | — | Jul 31 – Sep 4 | 60–100 |
| Larkspur | — | Apr 24 | — | — | Jul 3 – Aug 28 | 60–90 |
| Lavender | Mar 13 | — | Jun 12 | — | Aug 21 – Oct 2 | 90–120 |
| Lilies | — | Division | Jun 5 | — | Aug 14 – Nov 6 | 70–120 |
| Lobelia | Mar 13 | — | May 15 | — | Jul 10 – Sep 18 | 70–80 |
| Lupine | Mar 20 | Jun 5 | Jun 5 | — | Jul 31 – Sep 11 | 75–100 |
| Marigolds | Apr 10 | May 29 | May 29 | — | Jul 24 – Oct 16 | 50–70 |
| Nasturtium | Apr 24 | May 29 | May 29 | — | Jul 24 – Oct 30 | 55–65 |
| Pansy | Mar 13 | — | May 22 | — | Jul 17 – Sep 11 | 70–90 |
| Peonies | — | Division | Jun 5 | — | Aug 14 – Sep 25 | 90–120 |
| Petunia | Mar 27 | — | May 29 | — | Aug 7 – Oct 30 | 70–90 |
| Phlox | Mar 20 | Jun 5 | Jun 5 | — | Aug 21 – Nov 6 | 80–110 |
| Portulaca | Apr 17 | Jun 5 | Jun 5 | — | Jul 24 – Oct 23 | 50–70 |
| Roses | Mar 13 | — | Jun 5 | — | Aug 21 – Nov 20 | 90–180 |
| Salvia | Mar 20 | — | May 29 | — | Aug 7 – Oct 30 | 70–90 |
| Sedum (Stonecrop) | Mar 20 | — | Jun 5 | — | Oct 2 – Dec 4 | 60–90 |
| Snapdragon | Mar 13 | May 8 | May 22 | — | Jul 31 – Oct 2 | 70–100 |
| Sunflower | May 1 | May 29 | May 29 | — | Aug 21 – Oct 30 | 70–100 |
| Sweet Alyssum | Apr 3 | May 8 | May 22 | — | Jul 3 – Sep 11 | 45–60 |
| Sweet Pea | Apr 10 | Apr 17 | May 22 | — | Aug 7 – Oct 9 | 65–85 |
| Tulips | — | — | — | Aug 10 | Jul 13 – Aug 3 | 15–30 |
| Vinca (Annual) | Mar 6 | — | Jun 5 | — | Aug 14 – Oct 30 | 70–90 |
| Yarrow | Mar 20 | May 22 | Jun 5 | — | Aug 14 – Nov 20 | 60–90 |
| Zinnia | Apr 24 | May 29 | May 29 | — | Aug 7 – Oct 30 | 60–70 |
Monthly Planting Guide for Jefferson County
Gardening Guides & Resources
Helpful guides from The Ultimate Homestead to improve your garden in Jefferson County.
Frequently Asked Questions
What planting zone is Jefferson County, ID?
Jefferson 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 Jefferson County, ID?
Based on 31 years of NOAA weather station data, the median last spring frost in Jefferson County falls around May 22. In 8 out of 10 years, last frost lands between May 1 and June 17 — a 47-day window of variability. Use June 17 as your conservative safe-to-plant date for frost-sensitive crops.
When is the first fall frost in Jefferson County, ID?
The median first fall frost in Jefferson County arrives around September 21. In cold years it can arrive as early as September 4; 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 Jefferson County?
Jefferson County has a frost-free growing season of approximately 122 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 6.15 days per decade.
What is the soil like in Jefferson County for gardening?
Jefferson County has predominantly Loam soil with a pH range of 6.3–7.8 and Well Drained drainage. Most vegetables and herbs grow well with standard composting and seasonal soil amendment.
What is grown commercially in Jefferson County?
Jefferson County has commercial agriculture that includes Potatoes, Wheat, Hay, Dairy. These crops reflect the local climate and soil conditions — what succeeds commercially often translates well to home gardens in the same area.
Is Jefferson County a good location for home gardening?
Jefferson County scores 34/100 (Challenging) on our Microclimate Index, which combines frost reliability, drought pressure, soil challenge, elevation risk, and long-term climate trend. Gardening here benefits from close attention to frost timing and season extension due to the challenging microclimate factors.
Your Jefferson County Garden Planner — Free
A 22-page printable planner built for Jefferson 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