Planting Calendar & Schedule for Humboldt, IA

Understanding Your Planting Dates

How to read this chart

Each row shows a different plant, and the columns show the key steps for getting it started in your garden:

• Start Seeds Indoors — Begin seeds inside to get a head start on the season, especially in colder climates or for plants that need a long growing period.
• Transplant Outdoors — Move your seedlings outside once the weather and soil have warmed. This applies whether you grew the seedlings yourself or bought starter plants from a nursery.
• Direct Sow — Plant seeds directly into the ground. Some plants grow best this way because they don’t like being moved once they sprout. This method is sometimes called “direct sowing.”
• Last Planting Date — This is the final recommended date to plant for the season. Planting after this date may not leave enough time for the plant to mature before frost or cold weather.

Important: These are starting windows—not a guarantee that you can plant anytime between the first and last dates. Many cool-season plants—like lettuce and other tender greens—cannot grow through hot summer weather and will need to “take a break” until conditions cool again.

Using your planting dates

The dates in the chart show the earliest typical times to begin planting based on average frost dates for your area. These dates are a guide, not a guarantee, since weather varies from year to year. You don’t need to plant on the first date—just be sure to plant before the “Last Planting Date” so your plants have time to mature before frost.

Frost Dates Calculator

What “N/A” means

“N/A” indicates that the starting method isn’t typically recommended for that crop.

Past planting windows

If the Last Planting Date has passed, that crop will appear greyed out.

Why this chart isn’t zone-based

USDA zones describe winter temperatures and help gardeners choose perennial plants, whereas spring and fall frost dates determine when gardeners can plant vegetables. That’s why this calendar uses your ZIP code to provide more accurate planting dates for annual plants.

Planting Zone Guide

Optional Moon-favorable dates

If you prefer to follow traditional planting by the Moon, use the toggle above the chart to show dates aligned with the Moon’s phases. This feature is optional and does not change your frost-based planting windows.

Gardening by the Moon guide

Looking for flower planting dates?

Flower timing works differently from that of vegetables. Many flowers depend on hardiness, growth speed, and whether they’re annuals, perennials, or bulbs—not just frost dates.

Flower Planting Calendar and Guide