Question:
When can I plant flowers and vegetables in my garden this spring?Answer:
The last frost date in spring is the factor to consider when determining when to plant. The last frost date varies from year to year, but in most years it is late April in southern Iowa and mid-May in northern Iowa. As you approach the likely last frost day, look at the ten-day forecast. If temperatures below or near freezing are not predicted, it is safe to plant annuals and vegetables.
Frost and Freeze Dates in Iowa
When you can plant annuals or vegetables in the spring also depends on the type of plant.
Vegetables
Warm-season crops must be planted after the threat of frost has passed. Plants purchased from greenhouses or started indoors should be hardened off or acclimated to outdoor conditions for several days before planting. Initially, place plants in a shady, protected location and then gradually expose them to longer periods of sunlight.
Cool-season crops are plants that prefer cool temperatures and grow best in spring or fall. Many tolerate a light frost, often surviving down to 28°F or even 25°F with little damage to flowers or leaves. This means these crops can be planted up to 3 or 4 weeks before the last frost date in spring, depending on the crop.
Warm and Cool Season Vegetables
Annuals
Annuals can also be divided into warm- and cool-season types. Just like with vegetables, cool-season annual flowers can be planted several weeks before the last frost date in spring. The link below outlines cool-season annuals. Nearly all other annual flowers found in the garden center are warm-season plants and should only be planted outside after the threat of frost has passed, and they have been hardened off.