Columbia County, WA — Planting Guide
Columbia County is in USDA Zone 7a. The average last spring frost is April 28 and the first fall frost is October 11, giving you a growing season of approximately 166 days.
At an elevation of 3,157 ft, Columbia County receives approximately 21.4 in of rainfall annually. Summer highs average 90°F with winter lows around 24°F. The predominant soil type is Silt Loam.
Based on 29 years of NOAA climate station data, the last frost date here varies by 45 days year to year — ranging from April 3 in warm years to May 18 in cold years. The growing season is trending longer by about 1.35 days per decade. Columbia County scores 56/100 (Moderate) on the Microclimate Index.
🌡️ Zone
7a (0°F to 5°F min)
❄️ Last Frost
April 28
🍂 First Frost
October 11
📅 Growing Season
166 days
⛰️ Elevation
3,157 ft
🌧️ Annual Rainfall
21.4 in
Monthly Watering Calendar for Columbia County
When you'll need to water your garden — based on average monthly rainfall vs. the ~1 inch/week most gardens need.
Why it matters: Most vegetables want about 1 inch of water per week. Columbia County gets 21" a year — months that hit that 1"/week need zero supplemental watering; months that fall short, the table tells you how much to add. Saves you from drowning roots and from drought-stressing plants into bolting.
View detailed monthly data
| Month | Avg Rainfall | Rainy Days | Extra Water Needed | Watering Effort |
|---|---|---|---|---|
| Jan | 3 in | 18 days | — | None |
| Feb | 2.6 in | 13 days | — | None |
| Mar | 2.1 in | 16 days | 2.2 in | High |
| Apr | 1.7 in | 12 days | 2.6 in | High |
| May | 1.4 in | 9 days | 2.9 in | High |
| Jun | 0.9 in | 7 days | 3.4 in | Critical |
| Jul | 0.3 in | 3 days | 4 in | Critical |
| Aug | 0.3 in | 3 days | 4 in | Critical |
| Sep | 0.9 in | 4 days | 3.4 in | Critical |
| Oct | 1.9 in | 11 days | 2.4 in | High |
| Nov | 3 in | 19 days | — | None |
| Dec | 3.4 in | 17 days | — | None |
Annual total: 21.5 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.
Columbia County Soil Profile
Soil Type
Silt Loam
Soil pH
5.5-6.5
Drainage
Well Drained
Frost Risk Probability
Based on 29 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 18 | Oct 27 | 162 days |
| Cautious | May 7 | Oct 17 | 163 days |
| Average year | Apr 28 | Oct 11 | 166 days |
| Optimistic | Apr 18 | Oct 2 | 167 days |
| Aggressive (risky) | Apr 3 | Sep 22 | 172 days |
Not very — frost dates can vary by ±45 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 1.4 days per decade). Spring is arriving earlier than it used to. Good news for gardeners.
Gardening Difficulty Score
Columbia County presents some gardening challenges. Choose adapted varieties and plan around frost dates.
Local Gardening Help in Columbia 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 Columbia County's climate and soil.
County Extension Office
Columbia County Washington State University Extension Extension Office
Phone: 509-335-2811
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 Columbia County
Finding local nurseries & garden centers in Columbia County
Why Buy Local
Local nurseries carry plants that are proven to grow in your area. Staff can give you advice specific to Columbia 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 Columbia County WA" or "garden center Columbia 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 Columbia County WA" or check your extension office and local parks department. Facebook groups like "Columbia County Gardeners" or "Washington 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 Columbia County
Monthly daylight hours and peak sun — critical for onion varieties, photoperiod-sensitive plants, and solar garden planning.
Why it matters: Lettuce and cilantro "bolt" (go to seed) when days lengthen. Knowing your day-length curve helps you time spring plantings to harvest before the bolting trigger hits. Columbia County's daylight ranges shape the planting calendar.
Longest Day
15.6 hours
Summer solstice daylight
Shortest Day
8.4 hours
Winter solstice daylight
Peak Sun Hours
10.9 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 | 8.8 hr | 2.2 hr | Short day |
| February | 10.1 hr | 3 hr | Short day |
| March | 11.6 hr | 4.2 hr | Short day |
| April | 13.3 hr | 5.5 hr | Neutral |
| May | 14.8 hr | 7.3 hr | Long day |
| June | 15.6 hr | 8.6 hr | Long day |
| July | 15.2 hr | 10.9 hr | Long day |
| August | 14 hr | 9.4 hr | Long day |
| September | 12.3 hr | 7.4 hr | Neutral |
| October | 10.6 hr | 3.9 hr | Short day |
| November | 9.2 hr | 2.4 hr | Short day |
| December | 8.4 hr | 1.9 hr | Short day |
Peak sun hours factor in typical cloud cover — use these for solar panel and shade-planning calculations.
Soil Temperature & Composting in Columbia County
Monthly soil temps tell you when to plant warm-season crops, and when your compost pile is actively working.
The practical takeaway: Mulched soil swings less. The mulch insulates against both winter cold and summer heat. In Columbia County, an aggressive mulch program shifts your effective soil temperature curve toward optimal for most crops.
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 | 25°F | 29°F | ❄️ Dormant | ~36 weeks |
| Mar | 31°F | 34°F | ❄️ Dormant | ~36 weeks |
| Apr | 44°F | 42°F | 🐢 Slow | ~24 weeks |
| May | 56°F | 51°F | ♻️ Active | ~14 weeks |
| Jun | 67°F | 61°F | 🔥 Peak | ~8 weeks |
| Jul | 71°F | 68°F | 🔥 Peak | ~8 weeks |
| Aug | 72°F | 70°F | 🔥 Peak | ~8 weeks |
| Sep | 68°F | 66°F | 🔥 Peak | ~8 weeks |
| Oct | 55°F | 58°F | ♻️ Active | ~14 weeks |
| Nov | 40°F | 48°F | ❄️ Dormant | ~36 weeks |
| Dec | 29°F | 36°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 Columbia County
Computed from local climate patterns — warmer, humid conditions increase pest generations and fungal disease risk.
For new gardeners: The most successful gardeners in high-pressure regions don't spray more — they design around the problem. Crop rotation, companion planting, and resistant varieties beat reactive spraying.
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 | High | Apr, May, Jun, Jul, Aug, Sep |
| Japanese beetles | Moderate | Jun, Jul, Aug |
| Squash vine borers | Moderate | Jun, Jul |
| Tomato hornworms | Moderate | Jun, Jul, Aug |
| Cucumber beetles | Moderate | May, Jun, Jul |
| Stink bugs | Low | Jun, Jul, Aug, Sep |
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 Columbia County
Cover crops protect bare soil, fix nitrogen, suppress weeds, and improve soil structure — with planting dates calibrated for your area.
Why this matters: Bare soil is wasted soil — it loses nutrients to rain, dries out, compacts, and gets taken over by weeds. Cover crops (clovers, ryegrass, vetch, peas) are the "between seasons" trick that makes soil better every year. In Columbia County, you can fit a cover crop into the gaps.
Spring Cover Crops (3 options) — Build soil before the main growing season
| Crop | Plant By | Terminate | N-Fixing | Soil Benefit |
|---|---|---|---|---|
| Buckwheat | May 7 | Aug 9 | — | Rapid growth, attracts pollinators, suppresses weeds |
| Sorghum-sudan grass | May 7 | Aug 16 | — | Massive biomass, breaks compaction, suppresses nematodes |
| White clover | Apr 1 | Aug 16 | ✓ 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 27 | — | Deep roots break compaction, attract pollinators and beneficial insects |
Fall Cover Crops (7 options) — Plant after harvest to protect soil over winter
| Crop | Plant By | Terminate | N-Fixing | Soil Benefit |
|---|---|---|---|---|
| Austrian winter peas | Aug 5 | Apr 14 | ✓ Yes | Fixes nitrogen, good for heavy clay soils |
| Crimson clover | Aug 9 | Apr 7 | ✓ Yes | Fixes nitrogen, attracts pollinators in spring |
| Daikon radish | Aug 19 | Apr 7 | — | Deep taproot breaks compaction, excellent for clay soils |
| Hairy vetch | Aug 1 | Apr 14 | ✓ Yes | Excellent nitrogen fixer, good for depleted soils |
| Oats | Aug 30 | Apr 14 | — | Quick biomass, winterkills in cold zones — no spring tillage needed |
| Winter rye | Jul 13 | Apr 14 | — | Suppresses weeds, prevents erosion, breaks up compacted soil |
| Winter wheat | Jul 20 | Apr 7 | — | Erosion control, weed suppression, good biomass |
Wind & Microclimate in Columbia County
Why it matters: Pollinators avoid windy days. Columbia County's 9.0 mph average wind isn't enough to stop bees and butterflies — but plant fruiting crops (tomatoes, peppers, squash) in protected microclimates and you'll see noticeably better fruit set.
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: 12 mph
Prevailing wind: SW. Moderate wind — consider a temporary windbreak for young seedlings.
Windbreak Benefit
6.9/10
Moderately beneficial — a simple fence or trellis can protect delicate crops from wind stress.
Frost Pocket Risk
Moderate
Some terrain variation (645 ft range). Garden on slopes or higher ground if possible to avoid late-season frost pockets.
Rainwater Harvesting in Columbia County
How much water you can collect, when to collect it, and what size system you need for your garden.
Quick context: Most gardens use 0.5-1 gallon per square foot per week in summer. Columbia County's 21" annual rainfall is enough to cover most needs if you can capture it. Rain barrels under downspouts are the simplest entry point.
Annual Collection
10,715 gal
Per 1,000 sq ft of roof area (at 80% collection efficiency)
Recommended Setup
7 rain barrels (55 gal each)
For a typical 500 sq ft garden. Serious collectors: consider a 2,250 gal tank.
Legal Status
Unrestricted
Rainwater harvesting is fully legal in your state with no restrictions.
Best Collection Months
Jan, Feb, Nov, Dec
Highest rainfall months — your barrels will fill up quickly during these months.
Months to Draw From Storage
Jun, Jul, Aug, Sep
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 21.5 inches of rain per year
- A 1,000 sq ft roof can collect roughly 10,715 gallons annually
- Rainwater harvesting is fully legal in your state
- Stock up on stored water before your dry season (Jun, Jul, Aug)
- Use a first-flush diverter to keep roof debris out of your collection
Soil & Growing Conditions in Columbia County
Soil Type
Silt Loam
Soil pH 5.5–6.5 · Well Drained drainage
Native soil is well-suited to most vegetables and herbs with regular compost additions.
Watering Needs
Drought stress: 3.5/10
Low-to-moderate drought stress. Plan to water 1–2 times per week during peak summer. (21.4 in. annual rainfall)
Season Tips
166-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.
🥬 Vegetables to Grow in Columbia County
112 vegetables that grow well in Zone 7a with planting dates for Columbia County.
Show all 112 vegetables with planting dates
| Plant | Start Indoors | Direct Sow | Transplant | Fall Plant | Harvest | Days to Maturity |
|---|---|---|---|---|---|---|
| Acorn Squash | Mar 31 | May 5 | May 12 | — | Aug 4 – Sep 8 | 80–100 |
| Amaranth | Mar 10 | May 5 | May 12 | — | Aug 11 – Sep 29 | 90–120 |
| Artichoke | — | — | May 12 | — | Sep 15 – Nov 24 | 120–180 |
| Arugula | Mar 24 | Apr 14 | Apr 28 | Aug 2 | Jun 2 – Aug 4 | 30–50 |
| Asparagus | — | — | May 12 | — | — | 730–1095 |
| Beets | — | Apr 14 | — | Aug 2 | Jun 9 – Jul 7 | 50–70 |
| Belgian Endive | Mar 24 | Apr 14 | Apr 28 | Aug 2 | Aug 18 – Oct 13 | 110–150 |
| Bitter Melon | Mar 10 | May 5 | May 12 | — | Jul 14 – Aug 25 | 60–90 |
| Black Beans | — | May 5 | — | — | Aug 4 – Sep 22 | 90–120 |
| Bok Choy | Mar 24 | Apr 14 | Apr 28 | Aug 2 | Jun 9 – Jul 14 | 40–60 |
| Broccoli | Mar 24 | Apr 14 | Apr 28 | Aug 2 | Jun 30 – Aug 11 | 60–90 |
| Broccoli Rabe | Mar 24 | Apr 14 | Apr 28 | Aug 2 | Jun 9 – Jul 14 | 40–60 |
| Brussels Sprouts | Mar 24 | Apr 14 | Apr 28 | Aug 2 | Jul 28 – Sep 22 | 90–130 |
| Butternut Squash | Mar 31 | May 5 | May 12 | — | Aug 11 – Sep 15 | 85–110 |
| Cabbage | Mar 24 | Apr 14 | Apr 28 | Aug 2 | Jun 30 – Aug 25 | 60–100 |
| Calabash | Mar 10 | May 5 | May 12 | — | Aug 4 – Sep 29 | 80–120 |
| Cardoon | — | — | May 12 | — | Sep 15 – Oct 27 | 120–150 |
| Carrots | — | Apr 14 | — | Aug 2 | Jun 16 – Jul 21 | 60–80 |
| Cauliflower | Mar 24 | Apr 14 | Apr 28 | Aug 2 | Jun 23 – Aug 25 | 55–100 |
| Celeriac | Mar 24 | Apr 14 | Apr 28 | Aug 2 | Aug 11 – Sep 15 | 100–120 |
| Celery | Mar 24 | Apr 14 | Apr 28 | Aug 2 | Jul 21 – Sep 15 | 80–120 |
| Celtuce | Mar 24 | Apr 14 | Apr 28 | Aug 2 | Jun 30 – Aug 11 | 60–90 |
| Chard | Mar 24 | Apr 14 | Apr 28 | Aug 2 | Jun 23 – Aug 11 | 50–60 |
| Chayote | Mar 10 | May 5 | May 12 | — | Sep 15 – Nov 24 | 120–180 |
| Chickpeas | Mar 24 | Apr 14 | Apr 28 | Aug 2 | Jul 21 – Sep 1 | 80–110 |
| Chicory | Mar 24 | Apr 14 | Apr 28 | Aug 2 | Jun 30 – Aug 11 | 60–85 |
| Chinese Cabbage | Mar 24 | Apr 14 | Apr 28 | Aug 2 | Jun 23 – Jul 21 | 50–70 |
| Christmas Lima Beans | Mar 10 | May 5 | May 12 | — | Aug 4 – Sep 8 | 80–100 |
| Collard Greens | Mar 24 | Apr 14 | Apr 28 | Aug 2 | Jun 23 – Aug 25 | 55–75 |
| Corn | — | May 5 | — | — | Jul 7 – Sep 1 | 60–100 |
| Cowpeas | — | May 5 | — | — | Jul 7 – Aug 18 | 60–90 |
| Cress | Mar 24 | Apr 14 | Apr 28 | Aug 2 | May 12 – Jun 2 | 14–21 |
| Crookneck Squash | Mar 31 | May 5 | May 12 | — | Jun 30 – Jul 28 | 45–60 |
| Crosne | — | Apr 14 | — | Aug 2 | Sep 15 – Nov 17 | 150–200 |
| Cucumber | Mar 31 | May 5 | May 12 | — | Jul 7 – Sep 1 | 50–70 |
| Daikon | — | Apr 14 | — | Aug 2 | Jun 9 – Jul 7 | 50–70 |
| Delicata Squash | Mar 31 | May 5 | May 12 | — | Aug 4 – Sep 8 | 80–100 |
| Edamame | — | May 5 | — | — | Jul 21 – Sep 1 | 75–100 |
| Eggplant | Feb 24 | May 5 | May 12 | — | Jul 21 – Sep 22 | 65–85 |
| Endive | Mar 24 | Apr 14 | Apr 28 | Aug 2 | Jun 16 – Jul 21 | 45–65 |
| Escarole | Mar 24 | Apr 14 | Apr 28 | Aug 2 | Jun 23 – Jul 21 | 50–70 |
| Fava Beans | Mar 24 | Apr 14 | Apr 28 | Aug 2 | Jul 14 – Aug 25 | 75–100 |
| Fennel | Mar 10 | May 5 | May 12 | — | Jul 14 – Aug 25 | 60–90 |
| Garlic | — | — | — | Aug 30 | Nov 29 – Apr 11 | 90–240 |
| Green Beans | — | May 5 | — | — | Jun 30 – Aug 25 | 50–65 |
| Horseradish | — | — | May 12 | — | Sep 15 – Nov 24 | 120–180 |
| Hot Peppers | Feb 24 | May 5 | May 12 | — | Jul 21 – Oct 27 | 70–120 |
| Hubbard Squash | Mar 31 | May 5 | May 12 | — | Aug 25 – Sep 29 | 100–120 |
| Jicama | Mar 10 | May 5 | May 12 | — | Sep 15 – Nov 24 | 120–180 |
| Kabocha | Mar 31 | May 5 | May 12 | — | Aug 11 – Sep 8 | 85–100 |
| Kai Lan | Mar 24 | Apr 14 | Apr 28 | Aug 2 | Jun 16 – Jul 14 | 45–60 |
| Kale | Mar 24 | Apr 14 | Apr 28 | Aug 2 | Jun 23 – Aug 18 | 50–70 |
| Kidney Beans | — | May 5 | — | — | Aug 4 – Sep 8 | 85–110 |
| Kohlrabi | Mar 24 | Apr 14 | Apr 28 | Aug 2 | Jun 16 – Jul 21 | 45–65 |
| Komatsuna | Mar 24 | Apr 14 | Apr 28 | Aug 2 | Jun 2 – Jul 7 | 35–50 |
| Leeks | Mar 24 | Apr 14 | Apr 28 | Aug 2 | Jul 28 – Oct 13 | 90–150 |
| Lentils | Mar 24 | Apr 14 | Apr 28 | Aug 2 | Jul 21 – Sep 1 | 80–110 |
| Lettuce | Mar 24 | Apr 14 | Apr 28 | Aug 2 | Jun 2 – Aug 11 | 30–60 |
| Lima Beans | — | May 5 | — | — | Jul 7 – Aug 18 | 60–90 |
| Loofah | Mar 10 | May 5 | May 12 | — | Aug 25 – Oct 27 | 100–150 |
| Luffa | Mar 10 | May 5 | May 12 | — | Aug 11 – Oct 27 | 90–150 |
| Mache | Mar 24 | Apr 14 | Apr 28 | Aug 2 | Jun 9 – Jul 14 | 40–60 |
| Malabar Spinach | Mar 10 | May 5 | May 12 | — | Jul 7 – Aug 4 | 55–70 |
| Melon | Mar 31 | May 5 | May 12 | — | Jul 21 – Sep 8 | 70–100 |
| Microgreens | Mar 24 | Apr 14 | Apr 28 | Aug 2 | May 5 – Jun 2 | 7–21 |
| Mitsuba | Mar 24 | Apr 14 | Apr 21 | Aug 2 | Jun 16 – Aug 11 | 50–70 |
| Mizuna | Mar 24 | Apr 14 | Apr 28 | Aug 2 | Jun 2 – Jun 30 | 30–45 |
| Mustard Greens | Mar 24 | Apr 14 | Apr 28 | Aug 2 | Jun 2 – Aug 4 | 30–50 |
| Napa Cabbage | Mar 24 | Apr 14 | Apr 28 | Aug 2 | Jun 23 – Jul 28 | 55–75 |
| New Zealand Spinach | Mar 10 | May 5 | May 12 | — | Jul 7 – Aug 4 | 55–70 |
| Okra | Mar 10 | May 5 | May 12 | — | Jul 7 – Sep 1 | 50–65 |
| Onion | Mar 24 | Apr 14 | Apr 28 | Aug 2 | Jul 28 – Sep 15 | 90–120 |
| Pac Choi | Mar 24 | Apr 14 | Apr 28 | Aug 2 | Jun 9 – Jul 7 | 40–55 |
| Parsnip | — | Apr 14 | — | Aug 2 | Jul 28 – Sep 8 | 100–130 |
| Patty Pan Squash | Mar 31 | May 5 | May 12 | — | Jun 30 – Jul 28 | 45–60 |
| Peas | Mar 24 | Apr 14 | Apr 28 | Aug 2 | Jun 23 – Aug 18 | 55–70 |
| Peppers | Feb 24 | May 5 | May 12 | — | Jul 14 – Sep 22 | 60–90 |
| Pole Beans | Mar 10 | May 5 | May 12 | — | Jul 7 – Sep 1 | 55–70 |
| Potatoes | Mar 10 | May 5 | May 12 | — | Jul 21 – Sep 29 | 70–120 |
| Pumpkin | Mar 31 | May 5 | May 12 | — | Aug 11 – Sep 29 | 85–120 |
| Purslane | Mar 24 | Apr 14 | Apr 28 | Aug 2 | Jun 9 – Jul 14 | 40–60 |
| Radicchio | Mar 24 | Apr 14 | Apr 28 | Aug 2 | Jun 30 – Aug 4 | 60–80 |
| Radish | — | Apr 14 | — | Aug 2 | May 12 – Jun 2 | 22–35 |
| Rhubarb | — | — | May 19 | — | — | 365–730 |
| Romanesco | Mar 24 | Apr 14 | Apr 28 | Aug 2 | Jul 14 – Aug 25 | 75–100 |
| Rutabaga | — | Apr 14 | — | Aug 2 | Jul 7 – Aug 11 | 80–100 |
| Salsify | — | Apr 14 | — | Aug 2 | Jul 28 – Sep 8 | 100–130 |
| Savoy Cabbage | Mar 24 | Apr 14 | Apr 28 | Aug 2 | Jul 7 – Sep 1 | 70–110 |
| Scallions | Mar 24 | Apr 14 | Apr 28 | Aug 2 | Jun 23 – Jul 21 | 50–70 |
| Scarlet Runner Beans | Mar 10 | May 5 | May 12 | — | Jul 14 – Aug 18 | 60–80 |
| Shallot | Mar 24 | Apr 14 | Apr 28 | Aug 2 | Jul 28 – Sep 15 | 90–120 |
| Shiso | Mar 10 | May 5 | May 12 | — | Jul 7 – Sep 1 | 50–70 |
| Snap Peas | Mar 10 | May 5 | May 12 | — | Jul 7 – Sep 1 | 55–70 |
| Snow Peas | Mar 24 | Apr 14 | Apr 28 | Aug 2 | Jun 23 – Aug 18 | 50–65 |
| Soybeans | — | May 5 | — | — | Jul 28 – Sep 22 | 80–120 |
| Spaghetti Squash | Mar 31 | May 5 | May 12 | — | Aug 11 – Sep 8 | 85–100 |
| Spinach | Mar 24 | Apr 14 | Apr 28 | Aug 2 | Jun 2 – Aug 4 | 35–50 |
| Squash (Summer) | Mar 31 | May 5 | May 12 | — | Jun 30 – Sep 1 | 45–65 |
| Squash (Winter) | Mar 31 | May 5 | May 12 | — | Aug 4 – Sep 29 | 80–120 |
| Sunchoke | — | — | May 12 | — | Sep 1 – Oct 27 | 110–150 |
| Sweet Corn | — | May 5 | — | — | Jul 7 – Aug 18 | 60–90 |
| Sweet Potatoes | Mar 10 | May 5 | May 12 | — | Aug 11 – Sep 29 | 90–120 |
| Tatsoi | Mar 24 | Apr 14 | Apr 28 | Aug 2 | Jun 2 – Jul 7 | 35–50 |
| Tomatillo | Mar 10 | May 5 | May 12 | — | Jul 14 – Sep 22 | 60–85 |
| Tomatoes | Mar 10 | May 5 | May 12 | — | Jul 14 – Sep 22 | 60–85 |
| Turnip | — | Apr 14 | — | Aug 2 | May 26 – Jun 30 | 40–60 |
| Watercress | Mar 24 | Apr 14 | Apr 28 | Aug 2 | Jun 9 – Jul 14 | 40–60 |
| Watermelon | Mar 31 | May 5 | May 12 | — | Jul 21 – Sep 8 | 70–100 |
| Wax Beans | — | May 5 | — | — | Jun 30 – Aug 25 | 50–65 |
| Winter Melon | Mar 10 | May 5 | May 12 | — | Aug 11 – Sep 29 | 90–120 |
| Yard Long Beans | Mar 10 | May 5 | May 12 | — | Jul 7 – Aug 18 | 55–80 |
| Zucchini | Mar 31 | May 5 | May 12 | — | Jun 30 – Aug 25 | 45–60 |
🍓 Fruits to Grow in Columbia County
31 fruits that grow well in Zone 7a with planting dates for Columbia County.
Show all 31 fruits with planting dates
| Plant | Start Indoors | Direct Sow | Transplant | Fall Plant | Harvest | Days to Maturity |
|---|---|---|---|---|---|---|
| Alpine Strawberries | — | — | May 19 | — | Aug 18 – Dec 1 | 90–180 |
| Aronia | — | — | May 19 | — | — | 730–1095 |
| Blackberries | — | — | May 19 | — | — | 365–730 |
| Blueberries | — | — | May 19 | — | — | 730–1095 |
| Boysenberries | — | — | May 19 | — | — | 365–730 |
| Cantaloupe | — | — | May 19 | — | Jul 28 – Sep 1 | 70–90 |
| Che Fruit | — | — | May 19 | — | — | 1095–1825 |
| Cranberries | — | — | May 19 | — | — | 730–1095 |
| Currants | — | — | May 19 | — | — | 730–1095 |
| Elderberries | — | — | May 19 | — | — | 730–1095 |
| Figs | — | — | May 19 | — | — | 730–1825 |
| Goji Berries | — | — | May 19 | — | — | 730–1095 |
| Gooseberries | — | — | May 19 | — | — | 730–1095 |
| Grapes | — | — | May 19 | — | — | 730–1095 |
| Ground Cherry | — | — | May 19 | — | Jul 28 – Sep 22 | 65–80 |
| Hardy Kiwi | — | — | May 19 | — | — | 1095–1825 |
| Haskaps | — | — | May 19 | — | — | 730–1095 |
| Honeydew | — | — | May 19 | — | Aug 11 – Sep 22 | 80–110 |
| Jostaberry | — | — | May 19 | — | — | 730–1095 |
| Kiwi | — | — | May 19 | — | — | 1095–1825 |
| Lingonberries | — | — | May 19 | — | — | 730–1095 |
| Loquat | — | — | May 19 | — | — | 730–1825 |
| Medlar | — | — | May 19 | — | — | 1095–1825 |
| Mulberries | — | — | May 19 | — | — | 730–1825 |
| Pawpaw | — | — | May 19 | — | — | 1095–2555 |
| Persimmon | — | — | May 19 | — | — | 1095–2555 |
| Pomegranate | — | — | May 19 | — | — | 730–1095 |
| Quince | — | — | May 19 | — | — | 1095–1825 |
| Raspberries | — | — | May 19 | — | — | 365–730 |
| Serviceberries | — | — | May 19 | — | — | 730–1095 |
| Strawberries | — | — | May 19 | — | Aug 18 – Dec 29 | 90–365 |
🌿 Herbs to Grow in Columbia County
36 herbs that grow well in Zone 7a with planting dates for Columbia County.
Show all 36 herbs with planting dates
| Plant | Start Indoors | Direct Sow | Transplant | Fall Plant | Harvest | Days to Maturity |
|---|---|---|---|---|---|---|
| Angelica | Mar 24 | Apr 14 | Apr 21 | Aug 2 | — | 365–730 |
| Anise | Mar 24 | Apr 14 | Apr 21 | Aug 2 | Jul 21 – Oct 6 | 90–120 |
| Basil | Mar 10 | May 5 | May 12 | — | Jul 7 – Sep 8 | 50–75 |
| Bee Balm | — | — | May 5 | — | Aug 4 – Oct 20 | 90–120 |
| Borage | Mar 24 | Apr 14 | Apr 21 | Aug 2 | Jun 16 – Aug 4 | 50–60 |
| Caraway | Mar 24 | Apr 14 | Apr 21 | Aug 2 | — | 365–450 |
| Catnip | — | — | May 5 | — | Jul 7 – Sep 8 | 60–80 |
| Chamomile | Mar 24 | Apr 14 | Apr 21 | Aug 2 | Jun 23 – Sep 1 | 60–90 |
| Chervil | Mar 24 | Apr 14 | Apr 21 | Aug 2 | Jun 2 – Aug 4 | 40–60 |
| Chives | — | — | May 5 | — | Jul 7 – Sep 15 | 60–90 |
| Cilantro | Mar 24 | Apr 14 | Apr 21 | Aug 2 | Jun 2 – Aug 4 | 40–60 |
| Comfrey | — | — | May 5 | — | Jul 7 – Sep 15 | 60–90 |
| Cumin | Mar 24 | Apr 14 | Apr 21 | Aug 2 | Aug 4 – Oct 6 | 100–120 |
| Dill | Mar 24 | Apr 14 | Apr 21 | Aug 2 | Jun 2 – Aug 4 | 40–60 |
| Epazote | Mar 10 | May 5 | May 12 | — | Jun 30 – Aug 25 | 45–60 |
| Fennel (herb) | Mar 24 | Apr 14 | Apr 21 | Aug 2 | Jun 23 – Sep 1 | 60–90 |
| Feverfew | — | — | May 5 | — | Aug 4 – Oct 20 | 90–120 |
| Garlic Chives | — | — | May 5 | — | Jul 7 – Sep 15 | 60–90 |
| Horehound | — | — | May 5 | — | Jul 21 – Sep 15 | 75–90 |
| Hyssop | — | — | May 5 | — | Jul 14 – Sep 15 | 70–90 |
| Lemon Balm | — | — | May 5 | — | Jul 7 – Aug 25 | 60–70 |
| Lemon Thyme | — | — | May 5 | — | Jul 14 – Sep 15 | 70–90 |
| Lovage | — | — | May 5 | — | Jul 14 – Sep 15 | 70–90 |
| Marjoram | — | — | May 5 | — | Jul 7 – Sep 15 | 60–90 |
| Mint | — | — | May 5 | — | Jul 7 – Sep 15 | 60–90 |
| Oregano | — | — | May 5 | — | Jul 7 – Sep 15 | 60–90 |
| Parsley | Mar 24 | Apr 14 | Apr 21 | Aug 2 | Jun 23 – Aug 25 | 60–80 |
| Rosemary | — | — | May 5 | — | Jul 28 – Dec 15 | 80–180 |
| Rue | — | — | May 5 | — | Jul 14 – Sep 15 | 70–90 |
| Sage | — | — | May 5 | — | Jul 21 – Sep 15 | 75–90 |
| Savory | — | — | May 5 | — | Jun 30 – Aug 25 | 50–70 |
| Sorrel | Mar 24 | Apr 14 | Apr 21 | Aug 2 | Jun 2 – Aug 4 | 40–60 |
| Tarragon | — | — | May 5 | — | Jul 7 – Sep 15 | 60–90 |
| Thai Basil | Mar 10 | May 5 | May 12 | — | Jul 7 – Sep 8 | 50–75 |
| Thyme | — | — | May 5 | — | Jul 14 – Sep 15 | 70–90 |
| Valerian | — | — | May 5 | — | Sep 8 – Dec 15 | 120–180 |
🌸 Flowers to Grow in Columbia County
53 flowers that grow well in Zone 7a with planting dates for Columbia County.
Show all 53 flowers with planting dates
| Plant | Start Indoors | Direct Sow | Transplant | Fall Plant | Bloom | Days to Maturity |
|---|---|---|---|---|---|---|
| Ageratum | Mar 17 | Apr 28 | Apr 28 | — | Jun 23 – Oct 13 | 60–75 |
| Alliums | — | — | — | Sep 6 | Oct 4 – Oct 25 | 28–42 |
| Anemones | — | — | — | Aug 16 | Aug 30 – Sep 27 | 90–120 |
| Astilbe | Feb 24 | — | May 5 | — | Jul 14 – Sep 8 | 70–100 |
| Bachelor's Button | Mar 17 | Mar 24 | Apr 28 | Aug 16 | Jun 30 – Sep 29 | 60–90 |
| Begonias | Feb 17 | — | Apr 28 | — | Jul 7 – Oct 27 | 70–90 |
| Black-eyed Susan | Feb 24 | Apr 28 | May 5 | — | Jul 14 – Nov 17 | 60–80 |
| Bleeding Hearts | Feb 24 | — | May 5 | — | Jun 23 – Jul 28 | 60–90 |
| Calendula | Mar 17 | Mar 24 | Apr 28 | Aug 16 | Jun 16 – Sep 29 | 50–70 |
| California Poppy | — | Mar 31 | — | Aug 16 | Jun 9 – Aug 18 | 60–90 |
| Celosia | Mar 31 | Apr 28 | Apr 28 | — | Jun 30 – Oct 27 | 60–90 |
| Columbine | Mar 3 | May 5 | May 5 | — | Jun 23 – Jul 28 | 70–100 |
| Coreopsis | Feb 24 | Apr 28 | May 5 | — | Jul 7 – Nov 17 | 60–80 |
| Cosmos | Mar 31 | Apr 28 | Apr 28 | — | Jul 7 – Oct 27 | 60–90 |
| Crocus | — | — | — | Sep 6 | Aug 2 – Aug 23 | 10–20 |
| Daffodils | — | — | — | Sep 6 | Aug 9 – Aug 30 | 20–40 |
| Dahlias | Mar 31 | May 5 | May 5 | — | Jul 14 – Nov 17 | 70–120 |
| Daylily | Feb 24 | — | May 5 | — | Jul 14 – Nov 17 | 60–90 |
| Dianthus | Mar 3 | Mar 24 | Apr 7 | — | May 26 – Aug 25 | 60–80 |
| Echinacea (Purple Coneflower) | Feb 24 | May 5 | May 5 | — | Jul 21 – Nov 17 | 70–90 |
| Foxglove | Mar 3 | May 5 | May 5 | — | Jun 23 – Jul 28 | 80–120 |
| Gaillardia (Blanket Flower) | Mar 10 | May 5 | May 5 | — | Jul 14 – Dec 1 | 70–100 |
| Geraniums | Feb 17 | — | Apr 28 | — | Jul 7 – Oct 27 | 70–100 |
| Gladiolus | — | Apr 28 | Apr 28 | — | Jul 7 – Nov 10 | 70–100 |
| Hostas | Feb 17 | — | May 5 | — | Jul 14 – Nov 17 | 60–90 |
| Hyacinths | — | — | — | Sep 6 | Aug 30 – Sep 20 | 14–28 |
| Hydrangeas | Feb 17 | — | May 5 | — | Jul 14 – Nov 3 | 90–150 |
| Impatiens | Mar 3 | — | May 5 | — | Jul 14 – Nov 3 | 60–75 |
| Irises | — | Division | May 5 | — | Jun 23 – Jul 28 | 60–100 |
| Larkspur | — | Mar 31 | — | Aug 2 | Jun 9 – Aug 18 | 60–90 |
| Lavender | Feb 24 | — | May 12 | — | Jul 21 – Sep 29 | 90–120 |
| Lilies | — | Division | May 5 | — | Jul 14 – Nov 3 | 70–120 |
| Lobelia | Feb 24 | — | Apr 7 | — | Jun 2 – Aug 25 | 70–80 |
| Lupine | Mar 3 | May 5 | May 5 | — | Jun 23 – Jul 28 | 75–100 |
| Marigolds | Mar 17 | Apr 28 | Apr 28 | — | Jun 23 – Sep 29 | 50–70 |
| Nasturtium | Mar 31 | Apr 28 | Apr 28 | — | Jun 23 – Oct 27 | 55–65 |
| Pansy | Feb 17 | — | Apr 28 | Aug 2 | Jun 23 – Sep 1 | 70–90 |
| Peonies | — | Division | May 5 | — | Jun 30 – Aug 4 | 90–120 |
| Petunia | Mar 3 | — | May 5 | — | Jul 14 – Nov 3 | 70–90 |
| Phlox | Feb 24 | May 5 | May 5 | — | Jul 14 – Oct 6 | 80–110 |
| Portulaca | Mar 31 | Apr 28 | Apr 28 | — | Jun 16 – Oct 13 | 50–70 |
| Ranunculus | — | — | — | Aug 16 | Sep 13 – Oct 11 | 90–120 |
| Roses | Feb 17 | — | May 5 | — | Jul 14 – Nov 17 | 90–180 |
| Salvia | Mar 3 | — | Apr 28 | — | Jul 7 – Oct 27 | 70–90 |
| Sedum (Stonecrop) | Feb 24 | — | May 5 | — | Aug 25 – Nov 17 | 60–90 |
| Snapdragon | Feb 17 | Mar 31 | Apr 28 | Aug 16 | Jul 7 – Sep 29 | 70–100 |
| Sunflower | Apr 7 | Apr 28 | Apr 28 | — | Jul 21 – Oct 27 | 70–100 |
| Sweet Alyssum | Mar 17 | Mar 31 | Apr 28 | Aug 30 | Jun 9 – Sep 1 | 45–60 |
| Sweet Pea | — | Mar 24 | — | Aug 16 | Jun 2 – Aug 25 | 65–85 |
| Tulips | — | — | — | Sep 6 | Aug 23 – Sep 13 | 15–30 |
| Vinca (Annual) | Feb 17 | — | Apr 28 | — | Jul 7 – Oct 27 | 70–90 |
| Yarrow | Feb 24 | Apr 28 | May 5 | — | Jul 7 – Nov 17 | 60–90 |
| Zinnia | Mar 31 | Apr 28 | Apr 28 | — | Jul 7 – Oct 27 | 60–70 |
Monthly Planting Guide for Columbia County
Gardening Guides & Resources
Helpful guides from The Ultimate Homestead to improve your garden in Columbia County.
Frequently Asked Questions
What planting zone is Columbia County, WA?
Columbia County is in USDA Hardiness Zone 7a. 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 Columbia County, WA?
Based on 29 years of NOAA weather station data, the median last spring frost in Columbia County falls around April 28. In 8 out of 10 years, last frost lands between April 3 and May 18 — a 45-day window of variability. Use May 18 as your conservative safe-to-plant date for frost-sensitive crops.
When is the first fall frost in Columbia County, WA?
The median first fall frost in Columbia County arrives around October 11. In cold years it can arrive as early as September 22; in mild years as late as October 27. Harvest or protect frost-sensitive crops — tomatoes, peppers, basil, squash — before this date.
How long is the growing season in Columbia County?
Columbia County has a frost-free growing season of approximately 166 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 longer by about 1.35 days per decade.
What is the soil like in Columbia County for gardening?
Columbia County has predominantly Silt Loam soil with a pH range of 5.5–6.5 and Well Drained drainage. Most vegetables and herbs grow well with standard composting and seasonal soil amendment.
What is grown commercially in Columbia County?
Columbia County has commercial agriculture that includes Wheat, Hay, Apples, Potatoes, Cattle. These crops reflect the local climate and soil conditions — what succeeds commercially often translates well to home gardens in the same area.
Is Columbia County a good location for home gardening?
Columbia 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.
Your Columbia County Garden Planner — Free
A 22-page printable planner built for Columbia County (Zone 7a). 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