Cool Climate Vegetable Gardening: Seed Starting Schedule for Zones 5 & 6

Starting a vegetable garden from seed is rewarding but challenging, especially in cooler climates like USDA Zones 5 and 6 where unpredictable frosts and cold soil test a gardener's patience. This guide, adapted from a class at Phelan Gardens in Colorado Springs, provides a month-by-month planting calendar tailored to short-season regions—with principles applicable to similar zones nationwide.

Vegetable Planting Guide for Cool Climates

The chart below uses mid-month dates as benchmarks (e.g., "mid-April" not "April 1"). It covers spring planting through fall harvest windows, helping you avoid common mistakes like planting corn too early. Staggering quick-maturing crops ensures continuous production.

Vegetable	Mar	Apr	May	Jun	Jul	Aug	Sep
Asparagus	●	●	●
Beans			●	●	●
Beets			●
Broccoli		●			●
Cabbage		●
Carrots		●
Cauliflower		●
Collards		●			●
Corn			●
Cucumber			●
Eggplant			●
Garlic		●					●
Kale		●
Lettuce		●	●	●	●	●
Melon			●
Onion		●	●
Peas	●	●			●
Pepper			●
Potatoes	●	●
Pumpkin			●
Radish		●		●	●
Spinach		●				●
Squash			●
Tomatoes			●	●

● = optimal planting window

Short-Season Tomato Strategies

Tomatoes are the quintessential challenge for cool-climate gardeners. The growing season often isn't long enough for standard varieties to set fruit before cold nights return. Beyond season extenders like Wall O' Waters and cold frames, selecting early- to mid-season varieties is essential.

Recommended Short-Season Tomatoes

• 'Stupice'
• 'Fourth of July'
• 'Eva Purple Ball'
• 'Juliet'
• 'Bloody Butcher'
• 'Sheyenne'
• 'Oregon Spring'
• 'Jetsetter'
• 'New Big Dwarf'
• 'Polar Star'
• 'Sugar Baby'
• 'Gregori's Altai'
• Cherry/grape types: 'Sweet 100', 'Yellow Pear', 'Jelly Bean', 'Sungold', 'Spoon'

Other Short-Season Vegetables

Many crops naturally mature quickly and tolerate cool temperatures, making them ideal for short seasons:

• 'White Bush Scallop' Patty Pan Squash
• 'Sugar Baby' Watermelon
• 'Spacemaster' Cucumber
• 'Raven' Zucchini
• 'Speedy Sweet' Corn
• 'Norkotah Russet' Potato

Kohlrabi, leafy greens, radish, broccoli, green beans, peas, and carrots also produce rapidly. Stagger plantings every 2–3 weeks for a continuous harvest.

For more season-extension techniques, consult the Pacific Northwest Extension Service guides. With careful planning, even the coolest gardens can yield abundant harvests.

(Editor's Note: Originally published May 4, 2009. Comments welcome; original authors may not respond.)