Planting Guides

When to Plant Basil in Anchorage: Complete Guide + Best Varieties for Zone 4b

Anchorage, Alaska

USDA Zone 4b

Last Frost: May 20

Last updated: October 30, 2025

Learn when to plant basil in Anchorage with specific dates for Zone 4b's 118-day growing season. Expert advice for Alaska's challenging herb climate.

TTom Erikson

October 30, 2025

Basil plants growing successfully in Anchorage greenhouse with mountain backdrop showing Alaska growing conditions — — Image © PlantReference.org 2026

Quick Answer

Start basil seeds indoors March 25-April 8 in Anchorage. Transplant outdoors after May 20 when soil reaches 60°F consistently.

TL;DR

Growing basil in Anchorage requires starting seeds indoors by March 25-April 8 and transplanting after May 20. The 118-day growing season demands protected cultivation in greenhouses or containers that can move indoors. Focus on hardy varieties like Ocimum basilicum 'Genovese' and avoid heat-lovers like Holy Basil that won't mature in Alaska's short season.

Frequently Asked Questions

When should I start basil seeds indoors in Anchorage?

Start basil seeds indoors between March 25-April 8 for Anchorage's Zone 4b climate. This timing provides 6-8 weeks of indoor growth before transplanting after the last frost date of May 20. Seeds need consistent 75-80°F temperatures to germinate properly, which requires heat mats in Alaska's cool spring conditions.

Can I grow basil outdoors year-round in Anchorage?

No, basil cannot survive outdoors year-round in Anchorage due to freezing temperatures from September through May. Basil is extremely frost-sensitive and suffers damage when temperatures drop below 50°F. However, you can grow basil indoors during winter or treat varieties like Ocimum basilicum 'African Blue' as houseplants for continued harvests.

What basil varieties work best in Alaska's short growing season?

Ocimum basilicum 'Genovese', Ocimum basilicum 'Spicy Globe', and Ocimum basilicum 'Cardinal' perform best in Anchorage's 118-day growing season. These varieties mature in 60-75 days and tolerate cooler conditions better than heat-loving types like Thai or Holy Basil. Compact varieties like Spicy Globe require less maintenance in the short season.

How do I protect basil from Anchorage's cool summer nights?

Use row covers when nighttime temperatures drop below 55°F, grow basil in containers that can be moved to protected areas, and position plants near south-facing walls for heat reflection. Water-filled containers nearby provide thermal mass to moderate temperature swings. Never leave basil exposed when frost warnings are issued, even in summer.

Should I grow basil in containers or in-ground in Anchorage?

Container growing is strongly recommended for Anchorage basil cultivation. Containers allow you to move plants to optimal locations for heat and protection, provide better soil drainage and faster soil warming, and enable bringing plants indoors during unexpected cool spells. Use minimum 5-gallon containers for full-size varieties and 2-3 gallon containers for compact types like Ocimum basilicum 'Spicy Globe'.

When can I transplant basil outdoors in Anchorage?

Transplant basil outdoors between May 20-June 1, only after soil temperatures consistently reach 60°F and nighttime temperatures stay above 50°F. Check soil temperature with a thermometer rather than relying on air temperature. Cold soil permanently stunts basil growth, so patience is critical even if the calendar says it's time to plant.

How do I prevent basil from bolting in Anchorage's variable weather?

Remove flower buds immediately when they appear, harvest regularly to keep plants in vegetative growth, and provide consistent growing conditions without temperature stress. Even in Alaska's short season, hot July spells can trigger bolting. Regular harvesting every 7-10 days keeps plants productive and prevents the switch to reproductive growth.

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Tagged with

#basil planting Alaska #Zone 4b herbs #Anchorage gardening #short season basil #Alaska container gardening #basil seed starting #cold climate herbs #Genovese basil Alaska #basil frost protection #Alaska herb growing

Written By

Tom Erikson

Tom is a lifelong Alaskan who gardens in Anchorage, where the growing season is short but intense. He works for the state cooperative extension service and has spent years figuring out what works in a climate where the ground freezes deep, the growing season starts in late May, and you get 19 hours of daylight in June. Tom grows cold-hardy vegetables, maintains a collection of boreal-adapted perennials, and experiments with season extension using cold frames and row covers. He writes about the realities of northern gardening—the unique advantages (those long summer days produce remarkable growth) and the genuine limitations. Tom's tone is calm and practical, with the quiet humor of someone who's gardened through Alaskan winters for decades.