17 flowers to plant in May

May is a good month to plant marigolds, gladiolus, cosmos, dahlias, roses, nasturtiums, peonies, lilies, and more. In most areas, the last frost has passed by May and the soil is warm. Warm soil helps seeds sprout fast and helps tender bulbs and tubers start to grow. Here are 17 flowers to plant in May, with planting depth, spacing, and sun needs for each one.

1. Marigolds

Plant marigolds in May from seed or from garden center starts. They bloom fast and handle summer heat.

Choose a sunny location with well-drained soil. If planting seeds, sow them about ¼ inch deep and water gently. In warm soil they often sprout within a week. If using transplants, space them 8 to 12 inches apart depending on the variety. Water after planting and keep the soil slightly moist until they’re established.

2. Gladiolus

Gladiolus grows tall flower spikes that add height to a bed. It grows from corms. NC State Extension lists it as hardy in USDA zones 7 to 10. In colder zones, dig the corms in fall and store them indoors over winter.

Plant gladiolus after the danger of frost has passed. Iowa State University Extension advises: “Make successive plantings every 2 weeks for continuous bloom from mid-summer to early fall. Gladiolus corms bloom approximately 8 to 10 weeks after planting.” Plant the corms 4 to 6 inches deep in well-drained soil and full sun. Plant them in groups for a fuller look.

3. Cosmos

Cosmos are easy to grow in May once the soil has warmed. Most gardeners grow them from seed, though some nurseries sell starts. They bloom all summer with little care and draw pollinators.

Sow seeds directly into the garden about ½ inch deep and 6 to 12 inches apart. Choose a sunny spot, but don’t be too fussy about soil type (these plants will grow in most soils). Water after planting. Once seedlings appear, water less. Cosmos do best in dry conditions.

4. Dahlias

Dahlias are a staple for May planting. By May, the soil is warm enough to plant dahlia tubers in the ground.

Choose a sunny spot with well-drained, fertile soil. Plant the tubers 4 to 6 inches deep, with the growing eye facing up. Space them 18 to 24 inches apart. Dahlias will bloom from mid-summer through frost. Most of the larger plant cultivars benefit from staking as they grow.

5. Roses

Roses come in many colors, shapes, and sizes, from climbers to compact shrubs.

Plant roses in spring, from late March to May depending on where you live, or in fall. Avoid planting in the heat of midsummer. Water new roses often during the growing season and feed them so they keep blooming.

6. Nasturtiums

Nasturtiums grow fast and have edible flowers and leaves. Plant them in flower beds or in the corners of a vegetable garden. Trailing types spill over the edges of containers and raised beds.

Nasturtiums prefer full sun and need only average soil. Sow seeds about 1 inch deep and 8 to 12 inches apart. The seeds have a hard coat, so soaking them in water for a few hours before planting can help speed up germination. Avoid excess fertilizer rich in nitrogen, as it can encourage growing leaves over flowers.

7. Peonies

Peonies have large, full blooms and come back for decades. There are many peony varieties in a wide range of colors. In May, plant peonies that come in nursery pots. Plant bare-root peonies in fall.

Peonies need at least 6 hours of full sun a day to bloom well. They grow best in well-drained soil with a pH near neutral. Space them 3 to 5 feet apart. They grow slowly, but they become almost shrub-like once established.

Do not over-fertilize peonies, since too much fertilizer can cut down on blooms. Water during dry spells. Avoid soggy soil, which can lead to root rot.

8. Lilies

Lilies are easy to grow. They come in many colors, sizes, and flower shapes.

Pick a sunny spot with some shelter from wind for tall lilies. Plant the bulbs about 4 inches deep in well-draining soil. In heavy clay, build a raised, mounded bed with compost so water drains away from the bulbs.

Watch for pests such as aphids. Water when the soil is dry. A layer of compost mulch helps hold moisture.

Once established, lilies need little care. Cut off spent blooms to keep the plants tidy. Divide crowded clumps every few years.

9. Black-eyed Susans

Black-eyed Susans can be planted in May from either seeds or nursery starts. Choose a sunny location with well-drained soil. Sow seeds below the surface or plant transplants about 12 to 18 inches apart. Water after planting and keep soil moist until the plants are established. Plants grown from seed may not bloom the first year. After that, they return in future seasons with bright yellow flowers from mid-summer through fall.

10. Crocosmia

Crocosmia is an easy flower with bright red, orange, or yellow blooms. It looks tropical, but NC State Extension lists it as hardy in USDA zones 6 to 9.

Plant crocosmia corms in spring or fall. You can also buy young plants and set them out once the weather warms.

The flowers attract hummingbirds and butterflies. In zones where it is hardy, crocosmia comes back each year with little work.

11. Zinnia

Zinnias come in many colors, forms, and sizes. They make good cut flowers because the blooms last a long time in a vase.

Zinnias come in every color except blue. Most cultivars grow up to 3 feet tall, with single or double flowers from summer until frost. Give them full sun.

Dwarf zinnias have small, daisy-like flowers on short stems. Use them to edge garden beds and paths. They come in white, pink, lavender, purple, scarlet, yellow, gold, and bicolors.

12. Calendula

Calendula grows well when planted in May, especially in cooler climates. Sow seeds ¼ to ½ inch deep in well-drained soil with full sun to partial shade. Calendula tolerates cooler nights, so it’s a good early-season flower. Water regularly, especially during dry spells, and remove spent blooms to encourage more flowers. These cheerful yellow and orange blooms attract pollinators and are also edible, making them a useful addition to vegetable gardens.

13. Alyssum

Alyssum is a low, spreading plant most often sold in white, pink, or purple. By May, the soil is warm enough for alyssum seeds to germinate quickly, or for transplants to settle in with minimal stress.

You can sow seeds directly into well-drained soil in full sun to partial shade. Sprinkle them on the surface and press them in. Alyssum seeds need light to germinate, so don’t bury them under the soil.

If you’re using baby plants from the nursery, plant them about 6 to 8 inches apart. Water well after planting and keep the soil slightly moist until they’re established. Alyssum grows fast in warm spring weather and often begins blooming a few weeks after sowing.

In cooler zones, planting in May gives you blooms through early summer. In warmer zones, alyssum can bloom well into fall, especially if you trim it back after the first flush of flowers.

14. Sunflowers

Sunflowers are one of the easiest flowers to plant in mid-spring. Most gardeners plant them from seed than from nursery starts.

May is an ideal time to plant sunflowers, especially if your soil has warmed to at least 50°F (10°C) and there’s no more risk of frost. Choose a sunny spot with well-drained soil. Sunflowers grow best with full sun to grow strong stems and large blooms.

Loosen the top few inches of soil and clear away any weeds or debris to prepare the planting area. Sow sunflower seeds about ½ inch deep and space them 6 to 12 inches apart, depending on the variety. Some sunflowers stay compact at a few feet tall, while others can grow over ten feet high. Check your seed packet for the expected mature height and spacing recommendations. It will also list the estimated number of days from planting to bloom, which helps you plan your garden timeline.

Water after planting and keep the soil moist until the seedlings emerge (usually within 7 to 10 days). Once the plants are a few inches tall, thin them if needed so each has enough space to grow. Taller varieties may need staking later in the season, especially in windy areas.

15. Echinacea

Echinacea is a pollinator favorite native to North America. May is a good time to plant echinacea, also known as coneflower, especially in areas where the soil has warmed and the danger of frost has passed. May planting gives the roots time to grow strong before the heat of summer and often results in blooms by midsummer that last well into fall.

Choose a spot with full sun and well-drained soil. Echinacea tolerates poor soil but needs soil that doesn’t stay soggy. If your soil is heavy (like clay), mix in compost or sand to improve drainage before planting.

You can plant echinacea from nursery starts or sow seeds directly, though seed-grown plants may not bloom until the second year. Space plants about 18 to 24 inches apart to give them room to grow. Water well after planting and keep the soil moist while the plants get established. Once settled, echinacea is drought-tolerant and low-maintenance.

16. Lavender

Lavender is a good choice for May planting in most regions, especially once the soil has warmed and is no longer cold and soggy. Lavender loves full sun and well-drained soil. Choose a spot that gets at least 6 hours of direct sunlight each day. If your soil is heavy or clay-rich, mix in sand or gravel to improve drainage. Lavender does not like wet roots.

Plant nursery-grown lavender starts 18 to 24 inches apart to allow for air flow and mature size. Water well after planting, but let the soil dry out between waterings. Once established, lavender is drought-tolerant and thrives with minimal care. Planting in May gives your lavender starter plants time to settle in before summer heat and encourages flowering in the first season.

17. Sweet peas

Sweet peas can still be planted in May in cooler climates. In warmer areas, they are planted earlier, but you can start them in partial shade to help them through the summer.

Soaking the seeds overnight before planting can help with germination. Sow seeds 1 inch deep and 2 to 3 inches apart. Provide a trellis or support as sweet peas are natural climbers. Keep the soil moist and expect blooms in 60 to 70 days if conditions are right. Cut the flowers often to get more blooms.

Flowers to plant in May FAQs

Is it too late to plant flowers in May?

No. May is a good month to plant most summer flowers, including marigolds, zinnias, cosmos, and sunflowers. Plant after your last frost date.

Which bulbs can I plant in May?

Plant summer bulbs such as gladiolus, dahlias, lilies, and crocosmia in May once the soil is warm. Iowa State University Extension suggests planting gladiolus every 2 weeks until early July for blooms into fall.

Can I plant peonies in May?

Yes, if they come in nursery pots. Plant bare-root peonies in fall.

What flowers grow fast from seed in May?

Marigolds, cosmos, zinnias, nasturtiums, alyssum, and sunflowers sprout and grow fast in warm May soil.