Every spring we get the same question at the greenhouse: “Is it safe to plant yet?” Knowing when to plant flowers in Michigan depends on what you’re putting in the ground and where you are in the state. Here in Macomb County we’ve been growing flowers for years, and as most Michiganders know, one warm week in April doesn’t mean winter is done with us.
This guide walks you through what to plant and when — month by month, from the first cool-season seeds in March all the way through fall bulb planting in October. We wrote it for southeast Michigan gardeners specifically, but if you’re anywhere in zones 5b through 6a, most of the timing will work for you too. Just know your own last frost date and adjust from there.
When to plant flowers in Michigan: growing zones and frost dates
Most of southeast Michigan — including Macomb, Oakland, and Wayne counties — falls in zone 6a. That means average winter lows between -10°F and -5°F. Head up toward the Thumb or west toward Lansing and you’re in 5b, where it gets a bit colder. The zone tells you which perennials will survive winter and which annuals you can push earlier in spring.
Last frost dates for flower planting in southeast Michigan
For Macomb County and the surrounding area, the average last frost falls around May 10-15. Some years it’s earlier, some years we get a surprise frost in late May. We’ve seen it happen.
That date is your anchor. Frost-tender plants — your petunias, impatiens, tomatoes, peppers — go in the ground after it. Cold-hardy plants can go out weeks earlier.
When to plant flowers in Michigan in March and April
March in Michigan still feels like winter most days. But there’s already work to do if you want a head start on the season.
Cool-season vegetables to start early
By mid-March you can start seeds indoors for tomatoes, peppers, and eggplant. They need 6-8 weeks inside before transplanting, which lines them up perfectly for a late-May move outdoors.
Outside, once the soil thaws enough to dig (usually late March to early April), you can direct sow peas, spinach, lettuce, radishes, and kale. These cool-season crops actually prefer the cold. They’ll bolt once summer heat arrives, so getting them in early gives you the longest harvest window.
Hardy annuals and pansies
Pansies are the toughest annual flowers you can plant. They handle frost without flinching. You can plant them as soon as you bring them home — even if nighttime temps dip into the 20s. They come in almost every color, and they’ll keep blooming right through until the heat of June slows them down.
Snapdragons, violas, and dianthus are in the same category. They’ll give you color on the porch weeks before it’s safe to plant anything else. We put pansies in our own display wagons in early April and they look great through Mother’s Day. If you’re itching to garden in April, these are your plants.
When to plant flowers in Michigan in May (after last frost)
May is the main event in Michigan gardening. Once you’re past that mid-May frost date, the floodgates open.
Annual flowers: petunias, geraniums, impatiens, and more
This is what we grow the most of at the greenhouse, and for good reason — annuals give you nonstop color from Memorial Day through the first hard frost in October.
Petunias go in hanging baskets, porch pots, and garden beds. They want full sun and they’ll bloom all summer if you deadhead the spent flowers. Geraniums are another workhorse — tough, heat-tolerant, and they look great in containers. Impatiens are your shade plant. If you’ve got a north-facing porch or a spot under the trees, impatiens and begonias will thrive where sun-lovers won’t.
Calibrachoa (million bells) have become one of our best sellers. They look like tiny petunias, spill beautifully over hanging baskets, and they don’t need deadheading. If you haven’t tried them yet, grab a basket next time you stop by.
Plant all of these after May 15 in Macomb County. One late frost can wipe out a flat of impatiens overnight — we’ve seen it, and it’s not fun. If you’re unsure, keep an eye on the 10-day forecast. When nighttime lows stay above 45°F consistently, you’re in the clear.
Warm-season vegetables: tomatoes, peppers, squash
The same mid-May rule applies to your vegetable garden. Tomatoes, peppers, cucumbers, squash, and beans all need warm soil (at least 60°F) and no frost risk.
A tip we share at the stand every year: don’t rush tomatoes. A tomato planted May 20 in warm soil will outgrow one planted May 5 in cold soil every time. The plant just sits there and sulks until the ground warms up.
Herbs like basil, cilantro, and dill can go out at the same time. Basil especially hates cold — wait until nights are reliably above 50°F.
When to plant sunflowers in Michigan
Sunflowers are one of the most searched-for plants in Michigan, and the timing is simple: plant sunflower seeds directly in the ground in mid to late May, after your last frost date.
Don’t start them indoors. Sunflowers have a long taproot and they don’t transplant well. Just push the seeds about an inch into the soil, space them 6 inches apart, and thin to 12-18 inches once they sprout. Pick a spot with full sun — they’re called sunflowers for a reason.
Most varieties take 70-100 days from seed to bloom, which means a late-May planting gives you flowers in August and September. For a longer show, do a second sowing in mid-June. You’ll have sunflowers well into fall.
One thing people don’t always expect: sunflowers are heavy feeders. They’ll do fine in average Michigan soil, but a scoop of compost in the planting hole makes a real difference in stem thickness and flower size.
If you want the classic giant sunflower — the kind that towers over the fence — look for Mammoth or Russian Giant varieties. For cut flowers and bouquets, try ProCut Gold or Sunrich. The smaller branching types give you more blooms per plant, which is nice if you’re growing them for arrangements rather than height.
When to plant perennials in Michigan
Perennials — the plants that come back year after year — have a wider planting window than annuals. You can plant them in spring (April through June) or in early fall (September through mid-October).
Spring planting gives roots a full growing season to establish before winter. Fall planting works too, but you need to get them in the ground at least 4-6 weeks before the first hard frost so the roots can settle in.
Some perennials we see do especially well in Macomb County: coneflowers (echinacea), black-eyed Susans, daylilies, hostas, and bee balm. They all handle our clay soil, our winters, and our humidity. If you’re building a low-maintenance garden bed, these are where we’d start.
A few things to keep in mind with perennials: most won’t bloom heavily in their first year. The old saying is “first year they sleep, second year they creep, third year they leap.” Be patient. They’re an investment that pays off over time.
When you’re shopping for perennials, check the tag for sun requirements and mature size. A common mistake is planting something that needs full sun in a shady spot, or putting a 4-foot-tall plant in front of a 1-foot border. And don’t skip the mulch — 2-3 inches of shredded bark around your perennials keeps moisture in and weeds out, especially through that first summer while the roots are getting established.
Summer and fall planting (June through October)
The planting season doesn’t end in May. There’s plenty to do through summer and into fall.
June is a good time to succession plant beans, cucumbers, and summer squash for a second harvest. If you have gaps in the flower beds, fill them with annuals from the greenhouse — we’re stocked through July.
By July and August the focus shifts to fall planning. Start broccoli, cauliflower, kale, and Brussels sprouts indoors in July, then transplant them out in August for a fall harvest. Direct sow carrots and beets by early August — they actually taste sweeter after a light frost.
September is for mums, ornamental kale, and fall color. It’s also the best time to divide and transplant perennials — the cooler weather and fall rain help them establish without summer heat stress. If your coneflowers or daylilies have gotten too big for their spot, split them now and share the extras with a neighbor.
What can I plant in October in Michigan?
October still has plenty of planting to do. Here’s what goes in the ground before the freeze:
Spring-blooming bulbs — tulips, daffodils, crocuses, and alliums. Plant before the soil freezes, usually by mid-November in our area.
Garlic — push individual cloves 2 inches deep, mulch heavily, and forget about them until spring. October-planted garlic is ready to harvest the following July.
Cover crops — winter rye or crimson clover will hold the soil through winter. Turn it under in spring to add organic matter.
Trees and shrubs — the cooler temps and fall rain make October a good time for transplanting while the soil is still workable.
Michigan clay soil benefits from anything that adds organic matter — years of turning in cover crops and compost will slowly transform heavy clay into something your plants actually enjoy growing in.
FAQ: Michigan planting questions
When is it safe to plant flowers in Michigan?
Hardy annuals like pansies can go out in late April. Tender annuals — petunias, geraniums, impatiens — should wait until after the last frost, which falls around May 15 in southeast Michigan.
What month do you plant sunflowers in Michigan?
Plant sunflower seeds directly in the ground in mid to late May, after your last frost date. In Macomb County that’s typically around May 15. Sunflowers don’t transplant well, so direct sowing is the way to go.
What can I plant in October in Michigan?
October is the time for garlic, spring-blooming bulbs like tulips and daffodils, and cool-season cover crops. You can also transplant trees and shrubs while the soil is still workable.
Is it safe to plant annuals now in Michigan?
It depends on the date. Before mid-May, stick to cold-tolerant annuals like pansies, snapdragons, and violas. After May 15 in southeast Michigan, it’s safe to plant tender annuals like petunias, calibrachoa, and impatiens.
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We’re Oliver Greenhouse, a family flower grower on 24 Mile Road in Macomb, Michigan. We grow annuals, hanging baskets, porch pots, and vegetable starts right here at the greenhouse. Still unsure when to plant flowers in Michigan? Come visit us and we’ll help you figure out what can go out now and what should wait.
