Standing in the garden center in late May, you might think you’ve missed the window for planting annuals this year. I’ve definitely been there—staring at my empty flower beds while my neighbors’ gardens already burst with color, wondering if I’d have to wait until next spring.
Good news! Many fast-growing annuals can still catch up even when planted later in the season. With the right choices, you’ll have a stunning display of flowers in just a few weeks.
Not every annual is worth the late investment, though. Some need more time than the season has left, while others thrive when planted with summer heat just around the corner. Here’s what to grab—and what to leave behind—when you’re planting in late May.
1. Zinnias: The Late-Season Superstar
From seed to bloom in just 60 days, zinnias are the ultimate procrastinator’s friend in the garden. Their heat tolerance makes them perfect for late May planting when soil has thoroughly warmed up.
Plant them in full sun and watch them rocket upward, producing brilliant blooms until frost. The variety ‘Profusion’ series grows especially quickly, offering flowers in weeks rather than months.
My neighbor once planted zinnias on Memorial Day weekend and still had the most colorful yard on the block by mid-July. They’re practically foolproof for gardeners who are running behind schedule.
2. Cosmos: Quick Color With Minimal Fuss
Cosmos seeds sprout within days and race toward the sky at an impressive pace. Their feathery foliage creates an airy backdrop even before the daisy-like flowers appear about 7 weeks after planting.
These drought-tolerant beauties actually prefer poor soil—fertilizing them too much results in fewer flowers and more greenery. The ‘Sonata’ series reaches just 2 feet tall, making it perfect for borders without staking.
Last summer, I scattered cosmos seeds in late May in a neglected corner of my yard. By early July, those same spots were a sea of pink and white blooms that attracted countless butterflies.
3. Sunflowers: From Seed To Tower In Weeks
The rapid growth of sunflowers will amaze you—some varieties can shoot up 6 inches per week! For late May planting, choose shorter, quicker varieties like ‘Sunny Smile’ or ‘Teddy Bear’ that mature in just 60-70 days.
Direct sow the seeds where you want them to grow, as sunflowers dislike transplanting. Their deep taproot helps them withstand summer heat and drought once established.
A friend planted sunflower seeds along her fence on Memorial Day weekend, and by July 4th, she had an impressive display of sunny blooms that continued well into fall. Few plants deliver such dramatic results in such a short timeframe.
4. Marigolds: The Speedy Workhorse
Marigolds don’t mess around when it comes to quick results. Seed-grown plants flower in just 8 weeks, while nursery transplants bloom almost immediately after planting.
Their pest-repelling properties make them functional as well as ornamental. French marigolds mature faster than the larger African varieties, so opt for these if you’re in a hurry.
I’ve had great success tucking marigold transplants between slower-growing vegetables in late May. Not only did they brighten up the garden within days, but they also seemed to keep harmful insects away from my tomato plants all season long. Their ability to handle heat makes them ideal for late spring planting.
5. Morning Glories: Rapid Climbing Color
Morning glories actually prefer being planted directly in late spring when soil has warmed. Their vines grow with astonishing speed, sometimes adding several inches daily in warm weather.
Soak seeds overnight before planting to speed germination. Within 8-12 weeks, you’ll enjoy their trumpet-shaped blooms unfurling each morning.
The ‘Heavenly Blue’ variety has been my go-to for covering unsightly areas quickly. After planting seeds beside my mailbox post in late May last year, the vines had completely transformed it into a flowering column by August. For fastest results, choose a sunny spot and provide something for them to climb.
6. Nasturtiums: Edible Beauty In A Flash
Both the leaves and flowers of nasturtiums are edible, adding a peppery kick to summer salads. Their seeds germinate rapidly in warm soil, making late May an ideal planting time.
Choose mounding varieties like ‘Jewel Mix’ for containers or trailing types like ‘Gleam’ for hanging baskets. The plants flourish in poor soil and actually produce more flowers when not overfed.
After starting some nasturtium seeds in a window box last Memorial Day, I was garnishing plates with their bright blooms by early July. Their resilience to neglect makes them perfect for gardeners who don’t have time for fussy plants during busy summer months.
7. Bachelor’s Buttons (Cornflowers): Quick Blue Blooms
The classic blue flowers of bachelor’s buttons appear just 7-8 weeks after planting seeds. Their drought tolerance and preference for lean soil make them remarkably low-maintenance once established.
Direct sow the seeds where you want them to grow, as they don’t transplant well. The ‘Blue Boy’ variety is particularly fast to flower and produces abundant blooms.
These were my grandmother’s favorite quick-fix for bare spots in her garden. She’d scatter seeds in late May after removing spring bulb foliage, and by July, those patches would be covered in blue flowers that attracted pollinators all summer long.
8. Portulaca (Moss Rose): Heat-Loving Speed Demon
Portulaca thrives in conditions that would kill other annuals—blazing sun, poor soil, and drought. Their succulent leaves store water, making them virtually indestructible during summer heat waves.
The low-growing habit makes them perfect for edging, rock gardens, or containers. Flowers open in the morning and close in late afternoon, repeating the show daily for months.
I planted portulaca in a neglected strip along my driveway last May, an area where the reflected heat would wilt most plants. Within weeks, it formed a colorful carpet that required zero maintenance all summer. For quickest results, buy cell packs of started plants rather than growing from seed.
9. Calendula: Speedy Medicinal Beauty
Often called pot marigold (though unrelated to true marigolds), calendula produces daisy-like blooms in just 6-8 weeks from seed. Its edible petals add color to salads, while its medicinal properties have been valued for centuries.
The plants prefer cooler temperatures, making them ideal for northern gardens or partially shaded spots in southern regions. Deadhead regularly to encourage continuous blooming through summer.
My herb garden looked sadly empty in late May after I removed bolting lettuce. A quick sowing of calendula seeds filled the gaps beautifully by early July, providing both ornamental value and useful flowers for making skin-soothing salves. Their ability to self-seed means they’ll return year after year.
10. Annual Phlox: Instant Carpet Of Color
Annual phlox (Phlox drummondii) creates a fast-growing carpet of star-shaped blooms in just weeks. Unlike its perennial cousin, this quick-growing annual performs beautifully even when planted late in the season.
The ‘Twinkle Star’ mix offers unique star-shaped flowers with pointed petals. Plants stay compact at 6-8 inches tall, making them perfect for borders or containers.
When I needed to quickly fill in bare spots left by spring bulbs last year, annual phlox seedlings planted in late May created a seamless transition. By mid-June, the area was completely covered in blooms that continued until frost. For fastest results, purchase started plants rather than beginning from seed.
11. Sweet Alyssum: Fragrant Filler In No Time
The honey-scented blooms of sweet alyssum appear just weeks after planting. Their low-growing habit makes them perfect for edging beds or softening the edges of containers.
Heat-tolerant varieties like ‘Snow Princess’ or ‘Knight’ series continue blooming through summer without the mid-season break that older types require. Their cascading growth habit covers ground quickly.
Last year, I tucked alyssum transplants around newly planted roses in late May. By the time the roses began blooming in June, they were surrounded by a fragrant white carpet that attracted beneficial insects and pollinators. The plants kept going strong until frost, requiring almost no maintenance beyond occasional watering.
12. Celosia: Dramatic Plumes In Record Time
Celosia’s flame-like flower heads develop remarkably quickly, especially in warm soil. The feathery plumes or brain-like crests (depending on variety) appear just 8-10 weeks after planting.
Their tropical origins make them perfectly suited for late spring planting when soil has thoroughly warmed. The ‘Fresh Look’ series is particularly fast to bloom and holds up well in summer heat.
When I needed something dramatic for a bare spot near my patio last May, celosia transplants filled the bill perfectly. By July 4th, their vibrant red and gold plumes had reached full size, creating a conversation piece that lasted until frost. Their ability to dry right on the plant extended their ornamental value well into fall.
13. Impatiens For Sunny Spots
While impatiens grow quickly, planting them in late May often leads to disappointment in sunny locations. By this time, summer heat is approaching, and these shade-lovers simply can’t establish quickly enough to withstand direct sunlight.
Their shallow root systems make them especially vulnerable to drought stress during the establishment phase. When planted late, they often remain stunted or suffer from chronic wilting despite regular watering.
I learned this lesson the hard way after planting impatiens in a sunny border in late May. Despite daily watering, they struggled all season and never matched the vigor of those I’d planted in April in shadier spots. Save these for early spring planting or stick to shady locations for late starts.
14. Pansies And Violas
The sweet faces of pansies and violas are irresistible in spring displays, but planting them in late May is throwing money away in most regions. These cool-season bloomers begin to decline once temperatures consistently exceed 70°F.
When planted late, they rarely have time to establish before summer heat causes them to become leggy and stop flowering. Their compact form quickly deteriorates into sparse, stretched-out plants with few blooms.
The garden center near me often discounts pansies heavily in late May. Despite the tempting price, I’ve found they’re simply not worth the effort this late. Better to save your garden space and budget for heat-loving annuals that will perform all summer long.
15. Snapdragons From Seed
Starting snapdragons from seed in late May rarely produces satisfying results. These cool-weather lovers need months to develop from seed to flowering stage, making late starts problematic.
Snapdragons prefer to set roots during cooler spring temperatures. When started late, they often produce minimal blooms before fall weather arrives, giving little return on your effort.
I tried direct-sowing snapdragon seeds in late May several years ago, hoping for late summer blooms. The results were disappointing—spindly plants that produced just a few flowers before frost. If you love snapdragons and it’s already late May, purchase well-developed transplants instead of seeds.
16. Lobelia From Seed
The delicate blue flowers of lobelia are garden favorites, but starting them from seed in late May is an exercise in frustration. Their tiny seeds need 15-20 weeks from sowing to flowering—time the season no longer offers.
Lobelia also struggles during the heat of summer, often going dormant until cooler fall temperatures return. This makes late planting particularly problematic in warmer regions.
After an unsuccessful attempt at May-sown lobelia last year, I’ve learned to either plant established lobelia transplants in early spring or choose heat-tolerant alternatives like blue ageratum for late May planting. The newer ‘Heat Electric Blue’ variety shows better summer performance but still benefits from early planting.