Planting Guides

When to Plant Basil in Boston: Complete Guide + Best Varieties for Zone 6b

Boston, Massachusetts

USDA Zone 6b

Last Frost: Apr 20

Last updated: October 30, 2025

Learn when to plant basil in Boston with specific dates for Zone 6b. Compare varieties, get complete timeline, discover which basil grows best in Massachusetts.

KKevin Doyle

October 30, 2025

Basil plants growing in Boston garden with timing guide for Zone 6b Massachusetts planting — — Image © PlantReference.org 2026

Quick Answer

Plant basil in Boston after April 20 when soil temperature reaches 60°F. Start seeds indoors March 1-15 for transplanting after last frost.

TL;DR

Plant basil in Boston after April 20 when nights stay above 50°F. Start seeds indoors March 1-15 for best results. Genovese and Thai varieties thrive in Zone 6b's 183-day season. Harvest continuously through October for maximum yield.

Frequently Asked Questions

When is the latest I can plant basil in Boston?

You can plant heat-tolerant varieties like Thai and Holy basil as late as mid-July in Boston. These late plantings often produce excellent fall crops when cooler weather improves leaf quality. For best results, choose quick-maturing varieties and provide extra protection as temperatures cool in September.

Can I grow basil year-round indoors in Boston?

Yes, basil grows well indoors in Boston during winter months. Use grow lights providing 14-16 hours of bright light daily and maintain temperatures between 65-75°F. Indoor plants require excellent drainage and benefit from supplemental humidity during Boston's dry winter heating season.

Which basil variety produces the most in Boston's climate?

Genovese basil typically produces the highest yields in Boston gardens, often providing 1-2 pounds of leaves per plant over the growing season. Thai basil also produces heavily but requires more frequent flower removal. Purple varieties generally produce less but offer unique culinary and ornamental value.

How do I prevent my basil from going to seed too quickly?

Prevent bolting by harvesting regularly and removing flower spikes immediately when they appear. In Boston's climate, Thai and Lemon basil varieties are particularly prone to early flowering during hot July weather. Cut stems just above leaf pairs rather than picking individual leaves to encourage continued growth.

What should I do if my basil leaves turn black in Boston?

Black leaves on basil typically indicate chilling injury from temperatures below 50°F, which can occur during cool Boston nights in May or September. Remove damaged leaves immediately and provide protection during future cold spells. Plants usually recover if root systems remain healthy.

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Written By

Kevin Doyle

Kevin is a landscape contractor in the Boston area who specializes in cold-climate perennial gardens and hardscaping. He studied landscape design and worked at a prominent nursery on the North Shore before starting his own design-build firm. Kevin's gardens are built to handle New England weather—freeze-thaw cycles, nor'easters, late springs, and heavy snow loads. He's particularly interested in native perennials and shrubs that provide four-season interest without constant maintenance. Kevin writes about cold-hardy plant selection, winter garden structure, and building landscapes that look good even in February.