11 Flowers to Direct Sow in May

While spring is unpredictable, by mid-May, most of us are in the clear when it comes to frosts. Our friends at high elevations and northerly climates (one more month, Nome) remain susceptible to chill blasts and can start seeds indoors for transplanting in June. In many areas, the spring transition is sweeping the garden and making way for warm-season color, from perennials emerging to seed sowing.

May brings ideal planting and growing conditions with its cool nights and warm, sunny days for germination and growth. This month is prime for direct sowing flower seeds. Some are best sown before the final frost, while others need warm air and soil temperatures. Our list of flowers to direct sow in May includes those for post-frost seeding, from one to two weeks to two to four weeks after.

Your climate and plant selection determine the best planting timeline. In warm climates, you’re likely well underway with seeding and planting warm-season blooms in May, but the long growing season may warrant successional rounds. In cool climates, wait until soil temperatures warm to get the most success. Check seeding and packet guidelines in relation to your final frost date to make sure the selection is a fit for your May growing area.

Here are some of the best flowers to direct sow in May!

The Watchman Hollyhock

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The Watchman Hollyhock Seeds

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Bright Lights Blend Cosmos

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Bright Lights Blend Cosmos Seeds

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Teddy Bear Dwarf Sunflower

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Teddy Bear Dwarf Sunflower Seeds

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Zinnia

	botanical name Zinnia elegans
	sun requirements Full sun
	height 1-3′
	hardiness zones 2-11

Zinnias bring a sea of color to the annual display with their vibrant ray flowers from magenta to lime green to orange. The heat-loving blooms last from early summer through frost with little maintenance. Depending on the variety, blooms rise on single stalks or blanket low, mounding foliage.

Zinnias are a staple due to their ease of care, quick development, and profusion of blooms. Zinnias’ easy seeding adds to their appeal, with direct sowing as one of the best methods. Wait until a week or two after frost and when the soil warms to 70°F (21°C) or more to direct sow zinnias. The cold-sensitive annual won’t show strong germination until conditions are warm enough.

For a fresh supply of blooms all season, consider succession planting. Sow another round of seeds every two to three weeks until early summer for a nonstop bloom show.

Zinnias respond well to deadheading and regular harvesting, when they produce more flowers. The edible blooms are pretty as garnish for summer beverages and desserts. For the best vigor, ensure well-drained soil and good air circulation to prevent pests and fungal diseases, especially in humid climates.

Sunflowers

	botanical name Helianthus spp.
	sun requirements Full sun
	height 1-15′
	hardiness zones 2-11

May is the perfect time to direct sow sunflowers, as they grow quickly from seed and relish warm weather. Direct sow the sun-worshippers starting one to two weeks after the final frost. To maximize their impact, plant sunflowers in groups and seed two to three successional plantings so that when the first batch fades, another takes its place. Blooming through frost, the staggered seeding guarantees all-season color.

From dwarf and fuzzy like ‘Teddy Bear’ to tall and stately like ‘Lemon Queen’, sunflowers offer high visual interest in color and form. Prolific seeds stand after blooms fade, creating a rich food source for songbirds and small mammals.

For a fast turnaround, opt for dwarf specimens. A speedy choice is ‘ProCut® Red’ with deep crimson flowers atop single five- to six-foot stalks. They bloom 50 days after sowing. ‘ProCut® Lemon,’ ‘Gold,’ and ‘White’ round out the series of early bloomers.

Cosmos

	botanical name Cosmos spp.
	sun requirements Full sun
	height 1-6′
	hardiness zones 2-11

Cosmos are nearly effortless flowers to direct sow in May. The sun-loving rays wave on tall stems throughout the summer and into fall. Native to the Americas, the annual wildflowers need little care to thrive. In vivid yellow, apricot, bright pink, lavender, red, and chocolate, a rainbow of pollinator-attracting blooms is at our fingertips.

Cosmos performs in hot, dry conditions with variable soils. They prefer average to lean soils, and too much water, fertilizer, or organic richness hinders their vigor. The flowers self-sow in the landscape and grow quickly if you direct sow in spring. Look for ‘Apricotta’ for a sweet twist with apricot-pink shades and yellow centers. The Fleuroselect Award Winner softens the look as a vivid neutral complement.

Plant lots of cosmos for the most impact. When flowers finish blooming and go to seed, cut stems back to 12 to 18 inches, and they rebloom quickly. Let the cut stems fall so new seeds germinate for the next generation of blooms.

Nasturtium

	botanical name Tropaeolum spp.
	sun requirements Full sun to partial shade
	height 1-2′
	hardiness zones 10-12

Nasturtium joins our easy-to-grow list of plants. Aim to direct sow these flowers one to two weeks after the final frost, or around May for most zones. The best germination occurs when soil temperatures are between 55-65°F (13-18°C). Nasturtium prefers cool, mild summers to trail and bloom. In warm climates, wait to plant until fall or late winter to enjoy as a cool-season annual.

With bright, tubular flowers in red, orange, and yellow, pollinators like hummingbirds, butterflies, and hawk moths visit for nectar. Nasturtiums are a cascading fit for beds, hanging baskets, window boxes, and containers. The edible leaves and flowers have a peppery taste and make a lovely garnish for salads and platters.

For a quick turnaround from seed, look for dwarf selections like ‘Tom Thumb’ and ‘Jewel Blend’ for compact habits and early maturing. Other varieties bring unique colors like ‘Black Velvet’ and ‘Cherry Rose.’ ‘Alaska’ has variegated foliage in blue-green and creamy white.

Hollyhock

	botanical name Alcea rosea
	sun requirements Full sun
	height 3-8′
	hardiness zones 5-9

Old garden favorites, hollyhocks are biennials or short-lived perennials with towering blooms that line tall, straight stems. In rich colors from heirloom varieties in velvety black to magenta, scarlet, and soft yellow, they create a showy back-of-the-border backdrop.

Hollyhocks bring bold drama to the garden display and the vase. Shorter varieties are versatile in smaller spaces and don’t require staking like statuesque ones, whose stalks can reach eight feet tall. Fast to grow from seed, they’re ready to sow about one to two weeks after the final frost. 

Hollyhocks reseed readily and are invasive in some areas. They grow best in moist, organically rich soils.

Amaranth

	botanical name Amaranthus spp.
	sun requirements Full sun
	height 2-4′
	hardiness zones 2-11

Amaranth is a historic grain grown for its protein-rich seeds (also a favorite for songbirds). The highly ornamental tassel flowers in pendulous or upright plumes decorate as a spectacular annual. 

Flowering from late summer through frost, amaranth also adds lasting color and texture to fresh and dried floral designs. ‘Emerald Tassels’ and ‘Coral Fountain’ feature ropes of trailing blooms. ‘Hot Biscuits’ bears mellow amber and tawny plumes for a warm, textural filler.

Enjoy the splash of contrast for visual interest, and leave some blooms standing to go to seed. The seeds dry on the stem as a late-season food source for foraging birds.

Marigolds

	botanical name Tagetes spp.
	sun requirements Full sun
	height 6″-3′
	hardiness zones 2-11

Marigolds are tough annuals with sunny pompom blooms and hidden powers as companion plants for herbs and vegetables. Their minty aroma and chemical makeup repel certain pests while attracting other beneficials. African marigolds have the highest concentration of these compounds.

Marigolds bloom reliably, sometimes taking a break during peak summer heat to resume once temperatures moderate. They grow quickly from seed in warm, well-drained soils. Direct sow these flowers in May, one to two weeks after the last frost and when soils warm to 70-80°F (21-27°C).

French marigolds produce large single or double pompoms. In yellow, gold, and garnet, the frilled petals contrast handsomely with feathery, dark green foliage. ‘Lemon Drop’ delights with cheerful color, prolific blooms, a dwarf habit, and aromatic leaves and petals. ‘Red Metamorph’ is deep scarlet in cool temperatures and takes on splashes of yellow in warm weather. At two to three feet tall, it creates a lovely blooming hedge border.

Starflower

	botanical name Lomelosia stellata
	sun requirements Full sun to partial shade
	height 18-24″
	hardiness zones 2-11

Starflowers form intricately patterned seed pods with high visual interest. Their light periwinkle blue flowers open to papery, cupped seedheads with dark, starry, five-pointed centers. The arrangement of creamy cups forms small spheres at one and a half inches across.

The little globes add high detail to the cutting garden and fresh and dried florals. The annuals flower prolifically from mid-summer through frost for harvests at both bloom and seed stages. Multibranching stems are long and thin with silvery-green leaves.

Starflowers are deer-resistant and attract pollinators. Scatter them in well-draining soils with light coverage at ⅛ inch deep. Soils near 65-70°F (18-21°C) are ideal for germination.

Strawflower

	botanical name Xerochrysum bracteatum
	sun requirements Full sun to partial shade
	height 1-5′
	hardiness zones 8-10

Strawflower has stiff, papery blooms that run from spring until frost. The daisy ray petals with disk florets are also called “everlastings” because they hold their red, yellow, and pink colors on the stem and in fresh and dried arrangements.

Carefree annuals, strawflower is drought-tolerant and grows in average to dry soils. Deadhead faded flowers to encourage new shoots and more blooms.

‘King Size Silvery Rose’ is supersized with three to four-foot stems and double blooms in white, soft rose, and pink shades. ‘Silvery Rose’ dries to light silver to brighten arrangements. Direct sow these two to four weeks after the last frost.

Gomphrena

	botanical name Gomphrena globosa
	sun requirements Full sun to partial shade
	height 1-4′
	hardiness zones 2-11

Gomphrena is an old-fashioned, durable performer with papery pink, red, gold, magenta, or white flowers. The perfectly globe-shaped, cheery pompom blooms bring a burst of long-flowering color to the border. The tough summer annual that withstands heat, humidity, and dry conditions. It may overwinter in warm climates and even reseed, but not aggressively.

‘Fireworks’ is a favorite for its easy growth, tall stems, and hot pink powder puffs. Each puff glows with detailed bright yellow tips. ‘Fireworks’ has an airy texture, blooms more prolifically than other gomphrenas, and reaches three to four feet tall to float above other plants.

‘QIS Fiery Sunrise Blend’ strikes in reds, pinks, and oranges. A significant pollinator draw with recurrent color, the petite blooms are cut-and-come-again. Lasting on the stem and in a vase, this easy wave of color is best direct-sown two to four weeks after the last frost.

Scarlet Sage

	botanical name Salvia coccinea
	sun requirements Full sun to partial shade
	height 2-3′
	hardiness zones 9-11

Salvia coccinea is a compact sage with a neat habit and spikes of red tubular flowers that bloom from early summer through frost. Emerging earlier than other salvias, the North American native species has cultivars in pink, white, and coral. ‘Coral Nymph’ bears warm, coral-pink blooms, while ‘Summer Jewel Pink’ sparkles in pure pink.

Direct sow seeds in warm climates anytime and in cool climates post-frost and as soil temperatures warm (for a late bloom). The seeds need light to germinate, so sow them by pressing them lightly into the soil surface. Keep the site moist and look for germination in two to three weeks.

Scarlet sage is heat and drought-tolerant and grows with little tending. Remove faded bloom spikes to promote more flowers. While it perennializes in warm, frost-free zones, it grows quickly as an annual in cooler areas. It also reseeds in zones 6 and above for successional seasons of color. As a bonus, the aromatic foliage is deer and rabbit-resistant.