Planting Guides

When to Plant Cucumbers in Boise: Complete Guide + Best Varieties for Zone 6a

Boise, Idaho

USDA Zone 6a

Last Frost: May 5

Last updated: October 30, 2025

Plant cucumbers in Boise after May 20 when soil reaches 60°F. Zone 6a's 158-day season allows multiple harvests with proper timing and variety selection.

LLily Nakamura

October 30, 2025

Boise gardener transplanting cucumber seedlings into prepared garden bed in Zone 6a spring conditions — — Image © PlantReference.org 2026

Quick Answer

Plant cucumber seeds indoors April 20-25, transplant outdoors May 20. Direct sow from May 25 through July 15 for continuous harvest.

TL;DR

Plant cucumbers in Boise after May 20 when soil temperatures reach 60°F. Start seeds indoors April 20-25 for transplanting. Best varieties for Zone 6a include Cucumis sativus 'Marketmore 76', Cucumis sativus 'Boston Pickling', and Cucumis sativus 'Straight Eight'. Fall crop can be planted until July 15 for harvest before October 10 first frost.

Frequently Asked Questions

When is the last safe date to plant cucumbers in Boise?

July 15 is the absolute latest for planting cucumbers in Boise. This gives quick-maturing varieties like Cucumis sativus 'Boston Pickling' (50-55 days) time to produce before the October 10 average first frost. Plant only fast-maturing varieties for late-season success and consider row covers for frost protection.

Can I plant cucumbers earlier than May 20 in Boise if I use protection?

You can plant 1-2 weeks earlier using Wall O' Water plant protectors, cold frames, or row covers, but soil temperature is still critical. Even with air protection, cold soil (below 60°F) causes slow growth and potential root rot. Use soil thermometers to verify temperature before planting, regardless of air temperature protection.

Which cucumber varieties handle Boise's hot August temperatures best?

Cucumis sativus 'Lemon' cucumber excels in Boise's summer heat, rarely developing bitter compounds. Cucumis sativus 'Marketmore 76' also maintains quality through heat stress better than Cucumis sativus 'Straight Eight'. Provide afternoon shade cloth (30% density) when temperatures exceed 90°F consistently to prevent stress-induced bitterness.

How often should I water cucumbers during Boise's dry summers?

Water deeply twice weekly (1-1.5 inches total) during normal weather, switching to daily watering during heat waves above 85°F. Boise's low humidity increases water stress rapidly. Check soil moisture at 4-inch depth—it should be consistently moist but not waterlogged. Mulch heavily to reduce evaporation.

Do I need to start cucumber seeds indoors in Zone 6a or can I direct sow?

Both methods work in Boise's Zone 6a climate. Start indoors (April 20-25) for earliest harvest and to extend your growing season. Direct sowing works well from May 25 onward when soil warms reliably. Indoor starting gives you 3-4 weeks advantage and lets you plant through black plastic mulch for faster establishment.

What's the best succession planting schedule for continuous cucumber harvest in Boise?

Plant every 3 weeks: May 25 (spring crop), June 15 (main season), July 15 (fall crop). This provides continuous harvest July through October while spreading disease and pest risk. Focus on Cucumis sativus 'Boston Pickling' for later plantings as it handles variable fall weather better than slicing varieties.

How do I know when soil is warm enough for cucumber planting in Boise?

Use a soil thermometer at 4-inch depth—wait until temperatures consistently reach 60°F, ideally 65-70°F. This typically occurs around May 20-25 in Boise. Air temperature can be deceiving; cold soil causes seed rot and stunted growth even if air feels warm. Black plastic mulch can warm soil 5-10°F faster for earlier planting.

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#cucumber planting #Boise gardening #Zone 6a vegetables #cucumber varieties #Idaho gardening #cucumber timing #frost dates #succession planting #cucumber growing #garden planning

Written By

Lily Nakamura

Lily is a Master Gardener and high-desert homesteader outside Boise. She and her husband moved to Idaho from the Bay Area and had to completely relearn gardening for a climate with alkaline soil, intense sun, hard freezes, and limited water. Lily now grows a large vegetable garden, maintains a small orchard of cold-hardy fruit trees, and raises cut flowers for the local farmers market. She writes about the specific challenges of intermountain gardening—short seasons, temperature swings, and the importance of soil amendment in high-pH soils. Lily is honest about the learning curve: high-desert gardening is humbling, and she thinks more gardening writers should admit when conditions are genuinely difficult.