Planting Guides

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

Portland, Oregon

USDA Zone 8b

Last Frost: Mar 20

Last updated: October 30, 2025

Plant squash in Portland from mid-April through June for summer varieties, May 15-June 15 for winter types. Zone 8b's 235-day season supports all squash varieties.

DDr. Sarah Green

October 30, 2025

Butternut squash vines growing in Portland Oregon garden bed with Mt. Hood visible in background — — Image © PlantReference.org 2026

Quick Answer

Plant summer squash in Portland from mid-April through June, winter squash May 15-June 15. Portland's Zone 8b supports all varieties with proper disease management.

TL;DR

Plant squash in Portland from mid-April through June, with last frost March 19 and first frost November 9. Your 235-day growing season supports all varieties—summer squash mature in 50-60 days, winter squash need 80-110 days. Start seeds indoors March 1-15 or direct sow after soil reaches 60°F. Choose disease-resistant varieties for Portland's humid conditions.

Frequently Asked Questions

When should I plant squash in Portland Oregon?

Plant summer squash from mid-April through June when soil temperature reaches 60°F (15°C) consistently. Start winter squash May 15-June 15 to ensure 80-110 days before November 9 first frost. Direct seed after April 15 for main crop or start seeds indoors March 15-April 1 for earlier transplants.

What are the best squash varieties for Portland's Zone 8b climate?

Disease-resistant varieties perform best in Portland's humid conditions. Top choices include Cucurbita pepo 'Black Beauty' zucchini, Cucurbita moschata 'Waltham Butternut', Cucurbita maxima 'Blue Hubbard', and Cucurbita pepo 'Delicata'. These varieties resist powdery mildew and thrive in Portland's long, cool growing season.

How do I prevent powdery mildew on squash in Portland?

Proper spacing and air circulation are critical—space summer squash 36 inches (90 cm) apart, winter squash 6-8 feet (180-240 cm) apart. Water at soil level using drip irrigation, never overhead sprinklers. Apply preventive milk spray (1:9 ratio with water) starting in July. Choose resistant varieties and remove affected leaves immediately when spotted.

Can I grow winter squash successfully in Portland?

Yes, Portland's 235-day growing season is ideal for all winter squash varieties. Plant by June 15 for varieties needing 80-100 days, by June 1 for longer-season butternut (100-110 days). The mild fall weather allows full maturation before November frost, and proper storage conditions extend use through spring.

What spacing do squash need in Portland's humid climate?

Summer squash need 36-inch (90 cm) spacing between plants with 48-inch (120 cm) row spacing for adequate air circulation. Winter squash require 6-8 feet (180-240 cm) between plants and 8-10 feet (240-300 cm) between rows. Portland's humidity makes proper spacing critical for preventing fungal diseases like powdery mildew.

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Written By

Dr. Sarah Green

Sarah earned her doctorate in plant biology and spent time working in botanical garden education before transitioning to freelance writing and consulting. Now based in Portland, Oregon, she teaches plant identification workshops at local community centers and maintains a modest collection of over 60 houseplants in her small apartment. Sarah specializes in helping beginners understand plant science without the jargon—her approach focuses on practical observation over theory. She's killed her fair share of fiddle leaf figs and finally cracked the code on keeping them alive.