Planting Guides

When to Plant Tomatoes in Portland: Complete Guide + Best Varieties for Zone 8b

Portland, Oregon

USDA Zone 8b

Last Frost: Mar 20

Last updated: December 4, 2025

Learn when to plant tomatoes in Portland with specific dates for Zone 8b. Compare 6 varieties & discover which grow best in Oregon's maritime climate.

DDorothy "Dot" Williams

December 4, 2025

Portland tomato planting guide with seedlings ready for Zone 8b transplanting — — Image © PlantReference.org 2025

Quick Answer

Start tomato seeds indoors February 15-22 in Portland. Transplant outdoors April 2-9 after March 19 last frost for Zone 8b success.

TL;DR

Plant tomato seeds indoors February 15-22 in Portland for optimal Zone 8b success. Transplant outdoors April 2-9 after last frost risk passes on March 19. 'Stupice' and 'Early Girl' excel in Portland's cool maritime climate, while 'Cherokee Purple' thrives in the long 235-day growing season.

Product Recommendations

XLUX Soil Moisture Meter T10 Soil Test Kit

https://www.amazon.com/dp/B014MJ8J2U

This 3-in-1 meter tests soil moisture, pH, and light levels without batteries. The 7-inch probe measures Portland clay soil moisture at root depth. Essential for Portland's variable spring moisture and dry summer conditions. Prevents overwatering during cool periods and underwatering during hot stretches. Accurate pH readings help monitor soil amendments needed for clay soil improvement.

Price: $10.99-$14.99

Gardener's Supply Company Heavy Duty Tomato Ladder

https://www.gardeners.com/buy/heavy-duty-tomato-ladder/8593294.html

These 6-foot galvanized steel ladders support Portland's vigorous indeterminate varieties like Cherokee Purple and Brandywine. Built-in cross-rungs eliminate tying as plants grow. Weather-resistant coating handles Portland's wet springs without rusting. Easy assembly and seasonal storage. Accommodates the 8-10 foot growth potential in Portland's 235-day season.

Price: $24.95-$34.95

Wall O Water Season Extender Plant Protector

https://www.amazon.com/dp/B000BQUFXY

Water-filled chambers provide 10-15°F temperature protection around individual plants during Portland's variable spring weather. Allows safe April transplanting when nighttime temperatures drop to 35-40°F. Solar energy stored in water releases slowly at night, maintaining warmer root zone temperatures crucial for early growth. Reusable for multiple seasons with easy storage.

Price: $18.99-$24.99

Rain Drip R560DP Drip Irrigation Kit for Vegetable Gardens

https://www.amazon.com/dp/B000BQZPZO

Complete 100-foot drip irrigation system for gardens up to 250 square feet. Delivers consistent soil moisture tomatoes need during Portland's dry summers when rainfall drops below 1 inch monthly. Pressure-compensating emitters ensure uniform distribution regardless of elevation. Timer-compatible for automated watering during vacations. Reduces water waste and prevents leaf wetness.

Price: $39.99-$59.99

Bonide Copper Fungicide RTU Ready-to-Use Spray

https://www.amazon.com/dp/B004GUMAEC

Ready-to-use copper-based organic fungicide prevents late blight in Portland's maritime climate. OMRI-listed for organic gardening and safe until harvest day. Easy spray application without mixing. Essential during extended cool, wet periods when late blight pressure peaks. Protects susceptible heirlooms like Cherokee Purple and Brandywine.

Price: $12.99-$17.99

Frequently Asked Questions

When exactly should I start tomato seeds indoors in Portland?

Start tomato seeds indoors between February 15-22 for optimal Portland timing. This provides 6-8 weeks for strong seedling development before the April 2-9 transplant window. Portland's cool February indoor temperatures often require heating mats to maintain the 75-80°F (24-27°C) soil temperature needed for reliable germination.

What tomato varieties grow best in Portland's Zone 8b climate?

Solanum lycopersicum 'Stupice' and Solanum lycopersicum 'Early Girl' perform exceptionally well in Portland's maritime climate. Both varieties set fruit at cool temperatures (45-50°F nights) that persist through May in Portland. Solanum lycopersicum 'Cherokee Purple' thrives in Portland's moderate summers and long 235-day growing season, while Solanum lycopersicum 'Sungold' provides continuous cherry tomato production.

How do I protect tomatoes from Portland's late spring frosts?

Use Wall O Water season extenders or floating row covers for individual plant protection during cool April nights. Portland's March 19 average last frost can extend into early April in some years. Season extenders provide 10-15°F temperature protection, allowing safe April 2-9 transplanting even when overnight temperatures drop to 35-40°F.

When can I safely transplant tomatoes outside in Portland?

Transplant tomatoes April 2-9 in Portland, approximately two weeks after the March 19 average last frost date. Soil temperatures should consistently reach 55°F (13°C) before transplanting. Portland's variable spring weather makes waiting until early April safer than risking late March transplanting, even though statistical frost risk has passed.

What's the biggest challenge growing tomatoes in Portland?

Late blight disease poses the greatest threat to Portland tomatoes, thriving in our cool, moist spring and fall conditions. Prevent late blight with proper plant spacing, soil-level watering, and preventive copper fungicide applications during extended cool, wet periods. Choose resistant varieties like Solanum lycopersicum 'Early Girl' and remove infected plant material immediately.

How long is Portland's tomato growing season?

Portland enjoys a 235-day frost-free growing season from March 19 to November 9, providing excellent opportunities for both early and late-maturing varieties. This extended season allows heat-sensitive heirlooms like Solanum lycopersicum 'Brandywine' to reach full maturity while providing multiple harvests from early varieties throughout the season.

Should I grow tomatoes in containers or raised beds in Portland?

Raised beds work best in Portland due to our heavy clay soil and wet winter/spring conditions. Raised beds provide the drainage tomatoes need while warming faster in spring than ground-level plantings. If using containers, choose at least 20-gallon (76 L) sizes for indeterminate varieties and install drip irrigation to prevent the water stress that causes blossom end rot.

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Tagged with

#when to plant tomatoes Portland #Portland Zone 8b gardening #Oregon tomato planting guide #Pacific Northwest tomatoes #Portland gardening calendar #Zone 8b planting dates #Oregon vegetable gardening #Portland frost dates #maritime climate tomatoes #Pacific Northwest growing season

Written By

Dorothy "Dot" Williams

Dot grew up on a small farm in rural Virginia and has maintained a vegetable garden for decades. After retiring from teaching elementary school, she became a Master Gardener volunteer and spends her time mentoring new gardeners at community garden plots in Richmond. She's especially knowledgeable about heirloom varieties, seed saving, and traditional growing methods passed down from her grandmother. Dot's no-nonsense advice comes from extensive trial and error—she's seen every tomato disease, pest problem, and weather disaster imaginable. Her biggest pet peeve is gardeners who overcomplicate simple tasks. "Plants want to grow," she often says. "Your job is to not get in their way."