May garden tasks: Midwest
May is the month that Midwest gardeners have been waiting for since February. After months of indoor seed starting and cold-shoulder soil conditions, May delivers the warm-season planting window. But it delivers it across a very wide date range depending on.
May is the month that Midwest gardeners have been waiting for since February. After months of indoor seed starting and cold-shoulder soil conditions, May delivers the warm-season planting window. But it delivers it across a very wide date range depending on location.
Per UMN Extension, last frost dates: Minneapolis May 7, Chicago April 22, St. Louis April 7. A St. Louis gardener is already harvesting radishes and setting out squash while a Minneapolis gardener is still waiting for the last frost.
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Warm-season planting calendar
Per University of Illinois Extension:
Zone 6 (St. Louis, Columbus, Cincinnati) — plant May 1—15:
- Tomatoes, peppers, eggplant (transplant)
- Squash, cucumbers, melons (direct sow or transplant)
- Beans (direct sow when soil 60°F+)
- Basil, sweet corn
Zone 5 (Chicago, Milwaukee, Des Moines) — plant May 10—25:
- Tomatoes, peppers: May 10—15
- Basil: May 15—20
- Squash, cucumbers: May 15—20 (or direct sow)
Zone 4 (Minneapolis-St. Paul, northern WI) — plant May 15—June 1:
- Tomatoes: May 15—25
- Peppers: May 20—30 (very frost-sensitive; needs warmest soil)
- Squash, cucumbers: direct sow May 20 (fast germination means no head start needed)
- Basil: May 25—June 1
Per UMN Extension, when transplanting tomatoes and peppers into zone 4—5 soil in mid-May, soil temperature may still be in the 55—60°F range — functional but not optimal. Per UMN, black plastic mulch raises soil temperature 8—10°F over bare soil, improving early-season growth substantially.