Seasonal Action Guide
What to Do in the Garden in May (Cool-Climate US)
The short answer
May is the pivot month for cool-climate gardens. The headline jobs: harden off indoor-grown seedlings over about two weeks, then transplant or direct-seed heat-loving vegetables, sweet corn, beans, tomatoes, peppers, in mid-to-late May or the first week of June per University of Minnesota Extension, which is when frost danger typically passes in these zones. Plant annual flowers and summer bulbs from the last week of May, mulch beds, and begin fertilizing.
It's also the first harvest month: asparagus, rhubarb, and early sowings of radishes, spinach, and lettuce come in while the warm-season crops are just going out.
Plant and transplant
- Transplant or direct-seed heat-loving vegetables (sweet corn, beans, tomatoes, peppers) in mid-to-late May or the first week of June, after frost danger passes (UMN Extension).
- Harden off seedlings for about two weeks before transplanting: a few hours outside in shade at first, longer and sunnier each day (UMN Extension).
- Plant annual flowers from the last week of May through the end of June, the best window in the Upper Midwest.
- Plant summer bulbs from the last week of May through the second week of June, and perennials from late May onward.
- Move houseplants to shady spots outdoors only after frost danger has passed (Purdue Extension).
Prune and maintain
- Prune early-spring-flowering trees and shrubs as their blossoms fade, not before (Purdue Extension).
- Mulch beds; May through the end of June is the best window (UMN Extension).
- Begin season-long weed control (May through September) and start fertilizing from the last week of May.
- Lawns: early May through June is prime sodding time, and regular watering season begins (UMN lawn care calendar).
- Pinch chrysanthemums and annuals for compact, bushier growth.
Harvest
- Harvest asparagus by cutting or snapping spears at or just below soil level (Purdue Extension).
- Harvest rhubarb by grasping the stalk and pulling it up.
- Pick early plantings of radishes, spinach, and lettuce.
- Remove blossoms from newly planted strawberries so plants put energy into establishment.
Sources
Reviewed 2026-07-18. We cite university Extension, government, and established horticultural sources — and never invent pesticide rates or dangerous treatments.
- University of Minnesota Extension — Upper Midwest home garden care schedule — Heat-loving vegetables go out mid-to-late May or first week of June; annuals/summer bulbs/perennials from last week of May; mulch May-June; fertilize from last week of May; weed control May-September
- Purdue University Extension — May garden calendar (Indiana Yard and Garden) — Plant frost-tender plants once frost danger passes; prune spring bloomers after flowering; harvest asparagus, rhubarb, early greens; pinch mums and annuals; move houseplants out after frost
- University of Minnesota Extension — Starting seeds indoors — Harden off seedlings over two weeks before transplanting outdoors
Keep going
Garden Tasks for January (Warm-Climate US)
Seasonal Action Guide
Garden Tasks for February (Warm-Climate US)
Seasonal Action Guide
Garden Tasks for March (Warm-Climate US)
Seasonal Action Guide
Garden Tasks for March (Cool-Climate US)
Seasonal Action Guide
Garden Tasks for September (Cool-Climate US)
Seasonal Action Guide
Garden Tasks for April (Cool-Climate US)
Seasonal Action Guide
Garden Tasks for August (Cool-Climate US)
Seasonal Action Guide
Garden Tasks for December (Cool-Climate US)
Seasonal Action Guide