Pennsylvania’s May weather swings between cool nights and warm days, favoring flowers that adapt to temperature fluctuations. If you are searching for the best flowers to plant in may in pennsylvania, you need varieties that handle late frosts and sudden heat. This guide covers top picks, planting tips, and common mistakes to avoid.
May is a transition month. Soil warms up slowly, especially in northern counties. Rain is frequent, but dry spells can occur. Choose flowers that thrive in these conditions.
Best Flowers To Plant In May In Pennsylvania
These flowers perform well across Pennsylvania’s USDA zones 5 to 7. They tolerate cool nights, resist pests, and bloom from late spring through fall.
Marigolds
Marigolds are tough annuals that love the sun. They germinate quickly in warm soil. Plant them after the last frost date, usually mid-May in most areas.
- Varieties: French, African, and signet marigolds
- Sun: Full sun (6+ hours daily)
- Soil: Well-drained, average fertility
- Spacing: 8–12 inches apart
Marigolds repel nematodes and deer. They bloom until the first hard frost. Deadhead spent flowers to encourage more blooms.
Zinnias
Zinnias are heat-loving annuals that thrive in Pennsylvania’s May warmth. They come in many colors and sizes. Direct sow seeds after soil reaches 60°F.
- Choose a sunny spot with good drainage
- Sow seeds ¼ inch deep
- Water gently until seedlings emerge
- Thin to 6–18 inches apart depending on variety
Zinnias attract butterflies and bees. They resist powdery mildew if spaced properly. Cut flowers frequently for more blooms.
Petunias
Petunias are versatile annuals for beds, containers, and hanging baskets. They tolerate cool nights but need warmth to bloom heavily. Plant transplants after frost danger passes.
- Types: Grandiflora, multiflora, spreading
- Sun: Full sun to partial shade
- Water: Keep soil moist but not soggy
- Fertilizer: Use balanced liquid feed every 2 weeks
Petunias benefit from pinching back leggy stems. Remove faded flowers to prevent seed formation.
Snapdragons
Snapdragons are cool-season annuals that handle Pennsylvania’s May temperature swings. They bloom best in spring and fall. Plant them early in May for a long display.
These flowers come in dwarf, medium, and tall varieties. Tall types need staking. Deadhead regularly to extend blooming.
Cosmos
Cosmos are easy annuals from seed. They thrive in poor soil and full sun. Sow seeds directly in May after the soil warms.
- Height: 2–5 feet depending on variety
- Bloom time: June to frost
- Maintenance: Low; no fertilizer needed
Cosmos self-sow readily. Thin seedlings to prevent overcrowding. They attract pollinators and make excellent cut flowers.
Impatiens
Impatiens are shade-loving annuals that bloom from May until frost. They need consistent moisture and protection from hot afternoon sun. Plant transplants after soil warms.
New Guinea impatiens tolerate more sun than standard types. Watch for downy mildew in humid areas. Space plants 10–12 inches apart for good air circulation.
Begonias
Begonias are reliable for shady spots in Pennsylvania gardens. Wax begonias tolerate sun better than tuberous types. Plant them in May after frost risk ends.
- Water: Allow soil to dry slightly between waterings
- Soil: Rich, well-drained with organic matter
- Fertilizer: Use half-strength liquid feed monthly
Begonias bloom continuously until frost. Remove yellow leaves to keep plants tidy.
Sunflowers
Sunflowers are fast-growing annuals that love Pennsylvania’s May sun. Sow seeds directly after the last frost. Choose varieties suited to your space.
- Select a sunny location with shelter from wind
- Sow seeds 1 inch deep, 6 inches apart
- Water deeply once a week
- Thin to 12–24 inches apart for tall varieties
Sunflowers attract birds and bees. Harvest seeds for snacks or leave them for wildlife.
Lantana
Lantana is a heat-tolerant annual in Pennsylvania. It thrives in hot, humid weather. Plant transplants in May after soil warms thoroughly.
Lantana blooms in clusters of yellow, orange, pink, or red. It is drought-tolerant once established. Prune lightly to maintain shape.
Geraniums
Geraniums are classic annuals for beds and containers. They prefer cool nights and warm days. Plant them in May after frost danger passes.
- Sun: Full sun to partial shade
- Water: Let soil dry between waterings
- Deadheading: Remove spent blooms regularly
Geraniums can overwinter indoors if brought inside before frost. They are deer-resistant.
Dahlias
Dahlias are tender perennials grown as annuals in Pennsylvania. Plant tubers in May after soil reaches 60°F. They need full sun and rich soil.
Dahlias bloom from mid-summer until frost. Stake tall varieties. Water deeply once a week. Pinch early growth for bushier plants.
Cleome
Cleome, or spider flower, is a tall annual that adds drama to gardens. It self-sows readily. Sow seeds directly in May after frost.
Cleome tolerates heat and humidity. It attracts hummingbirds and butterflies. Remove spent flowers to control self-seeding.
Nasturtiums
Nasturtiums are edible annuals that thrive in poor soil. They bloom best in cool weather. Sow seeds directly in May after frost.
- Sun: Full sun to partial shade
- Soil: Poor to average, well-drained
- Water: Moderate; avoid overwatering
Nasturtiums repel aphids and whiteflies. Use flowers and leaves in salads.
Sweet Alyssum
Sweet alyssum is a low-growing annual that blooms from May to frost. It tolerates cool nights. Plant transplants or sow seeds directly.
This flower works well as a ground cover or border. It attracts beneficial insects. Trim back after first bloom to encourage reblooming.
Planting Tips For Pennsylvania Gardens
Follow these steps for success with May-planted flowers in Pennsylvania.
Prepare The Soil
Test soil pH before planting. Most flowers prefer pH 6.0–7.0. Amend clay soil with compost or aged manure. Sandy soil needs organic matter to retain moisture.
- Remove weeds and rocks
- Loosen soil to 8–10 inches deep
- Mix in 2–3 inches of compost
- Rake smooth before planting
Time Your Planting
Check your local frost dates. In Pennsylvania, last frost ranges from late April in the southeast to late May in the northwest. Use a soil thermometer to confirm soil temperature.
- Wait until soil reaches 60°F for warm-season flowers
- Plant cool-season flowers like snapdragons earlier
- Harden off transplants over 7–10 days
- Plant on overcast days or in late afternoon
Water Correctly
May can be rainy or dry. Water deeply once a week if rainfall is less than 1 inch. Avoid overhead watering to prevent fungal diseases.
Use drip irrigation or soaker hoses for best results. Water in the morning so foliage dries by evening.
Mulch And Fertilize
Apply 2–3 inches of organic mulch around flowers. Mulch conserves moisture and suppresses weeds. Use shredded bark, straw, or grass clippings.
Fertilize annuals every 2–4 weeks with a balanced fertilizer. Slow-release granules work well for low-maintenance gardens.
Common Mistakes To Avoid
Many gardeners make these errors when planting flowers in May. Avoid them for better results.
Planting Too Early
Warm-season flowers like zinnias and marigolds suffer in cold soil. Wait until soil temperature is consistently above 60°F. Planting too early leads to stunted growth or rot.
Overcrowding
Follow spacing recommendations on seed packets or plant tags. Overcrowded plants compete for water and nutrients. They also develop more diseases.
Ignoring Sun Requirements
Some flowers need full sun, others prefer shade. Check light conditions in your garden before buying plants. Place sun-lovers in south-facing beds.
Skipping Hardening Off
Transplants from greenhouses need gradual exposure to outdoor conditions. Hardening off over a week prevents shock. Start with a few hours of shade, then increase sun and wind exposure.
Regional Considerations For Pennsylvania
Pennsylvania’s climate varies by region. Adjust your flower choices based on your location.
Southeastern Pennsylvania
This area has milder winters and longer growing seasons. May is warm enough for most annuals. Plant heat-tolerant varieties like lantana and zinnias.
Central Pennsylvania
Central regions have moderate temperatures. May frosts are possible until mid-month. Choose resilient flowers like marigolds and petunias.
Northern And Mountainous Areas
These areas have shorter growing seasons and cooler nights. Plant cool-season flowers like snapdragons and pansies. Wait until late May for warm-season varieties.
Frequently Asked Questions
What are the best flowers to plant in May in Pennsylvania for shade?
Impatiens, begonias, and coleus thrive in shade. They bloom from May until frost with minimal care.
Can I plant perennial flowers in May in Pennsylvania?
Yes, perennials like coneflowers, black-eyed Susans, and daylilies can be planted in May. They establish well in warm soil.
How do I protect May-planted flowers from late frost?
Cover plants with frost cloth or old sheets overnight. Remove covers in the morning. Watering before frost can also protect roots.
What flowers bloom all summer in Pennsylvania?
Zinnias, marigolds, petunias, and cosmos bloom from June until frost. Deadhead regularly for continuous flowers.
Should I use seeds or transplants for May planting?
Seeds work well for fast-growing annuals like sunflowers and cosmos. Transplants give a head start for slower varieties like petunias and geraniums.
Final Thoughts On May Planting
May is an ideal month to start a colorful garden in Pennsylvania. The best flowers to plant in may in pennsylvania include marigolds, zinnias, petunias, and snapdragons. These varieties handle temperature swings and bloom for months.
Prepare soil properly, time planting correctly, and water consistently. Avoid common mistakes like planting too early or overcrowding. With these tips, your garden will thrive from spring through fall.
Experiment with different flowers each year. Note what works best in your microclimate. Gardening is a learning process, and May offers a great starting point for a beautiful season.