What to Plant in September by Zone: 12 Best Flowers & Seeds to Grow Now
What to Plant in September by Zone: 12 Best Flowers & Seeds to Grow Now
September is one of the most exciting months in the garden calendar. Depending on where you live, it's either the last hurrah of summer or the glorious beginning of your best growing season yet. Whether you're in a cool northern zone wrapping up the season or a warm southern zone just getting started, there are incredible flowers and seeds you can plant right now. This guide breaks it all down by USDA hardiness zone so you know exactly what to plant, when to start, and where to buy the best seeds.
At Trailing Petunia, we specialize in premium pelleted flower seeds — the kind that professional growers and passionate home gardeners trust for reliable germination and stunning results. Let's dig in.
September Planting by USDA Hardiness Zone
Before we get into the 12 best plants, here's a quick zone-by-zone overview so you can plan with confidence:
| Zone | September Climate | Best September Strategy |
|---|---|---|
| Zones 3-4 | First frost imminent; nights dropping fast | Start seeds indoors for spring; plant cold-hardy violas outdoors |
| Zones 5-6 | Cooling temps; frost possible late September | Direct sow snapdragons & violas; start lisianthus indoors |
| Zones 7-8 | Warm days, cool nights — ideal for cool-season flowers | Prime time for snapdragons, violas, stock, and lisianthus starts |
| Zones 9-10 | Still warm but beginning to cool — main growing season starts | Plant almost everything: snapdragons, zinnias, marigolds, lisianthus, gerbera, pentas |
| Zone 11+ | Tropical; heat easing slightly | Plant heat-tolerant varieties; begin cool-season starts indoors |
12 Best Flowers & Seeds to Plant in September
1. Snapdragons — The King of Fall Cool-Season Flowers
Best for: Zones 5-10 (direct sow or transplant); Zones 3-4 (start indoors)
Snapdragons are the undisputed champion of September planting. They love cool weather, tolerate light frost, and produce tall, elegant spikes perfect for cutting. September is the ideal time to direct sow or transplant snapdragons in Zones 7-10, where they'll bloom through fall and even into winter. In cooler zones, start them indoors now for strong spring transplants.
Our Snapdragon Rocket Mix produces tall, professional-grade cut flower stems in a gorgeous blend of colors. For something more refined, try our Monaco Plumblossom Snapdragon or the stunning Monaco Purple Snapdragon — both pelleted for precision planting.
Pro tip: In Zones 7-10, direct sow snapdragons in September for blooms by November-December. They'll reward you all the way through spring.
2. Lisianthus — The Luxury Cut Flower Worth Starting Now
Best for: Start indoors in all zones; transplant outdoors in Zones 8-10 by late fall
Lisianthus is the most luxurious cut flower you can grow from seed, and September is the perfect time to start them indoors. With a 5-6 month growing period, seeds started in September will produce breathtaking blooms by late winter or early spring — just in time for Valentine's Day and spring weddings.
Lisianthus requires patience but rewards you with rose-like blooms that last weeks in the vase. Our pelleted lisianthus seeds are professionally graded for maximum germination success. Browse our full lisianthus collection at Trailing Petunia.
Pro tip: Lisianthus needs warm soil (75-80F) to germinate. Use a heat mat and keep seedlings under grow lights for best results when starting in September.
3. Zinnias — Last Call for Warm-Zone Gardeners
Best for: Zones 9-11 (direct sow); Zones 7-8 (early September only)
In Zones 9-11, September is still prime zinnia territory. These fast-growing, heat-loving annuals will establish quickly in the still-warm soil and bloom prolifically before temperatures drop. In Zone 7-8, get seeds in the ground in early September for a final flush of color before frost.
Our Zinnia Crestar Mix is a premium cut flower variety with large, double blooms in a stunning color range — perfect for late-season bouquets and pollinator gardens.
4. African Marigolds — Bold Color for Warm Zones
Best for: Zones 8-11 (direct sow in September)
African marigolds planted in September in warm zones will establish strong root systems and deliver a spectacular show of giant blooms through fall. They're also excellent companion plants, deterring pests naturally while adding bold golden color to your garden.
Our Endurance Sunset Gold Triploid Marigold is a standout variety — massive blooms, exceptional heat tolerance, and a rich golden-orange color that glows in the fall garden.
5. Gerbera Daisy — Start Indoors for Spring Blooms
Best for: Start indoors in all zones; direct sow in Zones 9-11
Gerbera daisies are cheerful, long-lasting cut flowers that take 4-5 months from seed to bloom. Starting them indoors in September means you'll have gorgeous, vibrant blooms ready for late winter and spring. In Zones 9-11, you can direct sow in September for outdoor establishment.
Our Gerbera Daisy Royal Deep Pink Dark Eye is a showstopper — rich, saturated color with a dramatic dark center that makes every stem look like it came from a professional florist.
6. Violas — The Frost-Hardy Fall Favorite
Best for: All zones (Zones 3-6 direct sow early September; Zones 7-10 direct sow all month)
Violas are the workhorses of the fall garden. They're frost-tolerant, compact, and produce a continuous carpet of cheerful blooms well into winter in mild climates. September is the ideal time to direct sow violas in most zones — they establish quickly in cooling soil and will bloom right through the season.
Our Viola Admire White With Pink Wing is an elegant variety with crisp white petals and delicate pink markings — perfect for borders, containers, and window boxes.
7. Pentas — Pollinator Powerhouse for Warm Zones
Best for: Zones 9-11 (direct sow); Zones 7-8 (start indoors)
Pentas are a butterfly and hummingbird magnet, producing clusters of star-shaped flowers in vivid colors. In warm zones, September planting gives pentas time to establish before the peak of fall, delivering months of color and wildlife activity. They thrive in heat and are surprisingly drought-tolerant once established.
Our Honey Cluster Red Pentas is a premium pelleted variety with brilliant red star flowers that attract pollinators all season long.
8. Cineraria — Shade-Loving Color for Fall and Winter
Best for: Start indoors in all zones; direct sow in Zones 9-11
Cineraria (Pericallis) is an underrated gem for fall and winter color, especially in shaded spots where other flowers struggle. Starting seeds indoors in September gives you vibrant, daisy-like blooms in a rainbow of colors by late winter. They're perfect for pots, window boxes, and shaded garden beds.
Our Cineraria Resort Mix delivers a spectacular blend of jewel-toned colors — electric blues, purples, pinks, and reds — that light up shady spaces all winter long.
9. Sunflowers — Final Flush in Warm Zones
Best for: Zones 9-11 (direct sow early September)
In Zones 9-11, early September is your last window for a final flush of sunflowers before temperatures drop too low. Fast-maturing varieties can go from seed to bloom in 60-70 days, meaning you'll have gorgeous golden blooms by mid-to-late November.
Our Always Sunny Gold Sunflower is a compact, multi-branching variety that produces an abundance of cheerful golden blooms — perfect for cutting and containers.
10. Vinca — Heat-Tough Beauty for Warm September Gardens
Best for: Zones 9-11 (direct sow); Zones 7-8 (start indoors)
Vinca (Catharanthus) is one of the toughest, most reliable flowering annuals you can grow. It thrives in heat and humidity, making it perfect for warm-zone September planting. Vinca establishes quickly and blooms continuously with minimal care — ideal for borders, mass plantings, and containers.
Our Vinca Mediterranean XP Dark Red is a vigorous, heat-tolerant variety with rich, deep red blooms and a spreading habit that fills containers and beds beautifully.
11. Monaco Snapdragons — Premium Cut Flowers for Fall
Best for: Zones 6-10 (direct sow or transplant in September)
The Monaco series represents the pinnacle of snapdragon breeding for cut flower production. These professional-grade varieties produce exceptionally long stems, dense flower spikes, and outstanding vase life. September planting in Zones 6-10 sets you up for a spectacular fall and winter cut flower harvest.
Choose from our Monaco Plumblossom for a unique, soft lavender-pink tone, or the bold Monaco Purple for deep, dramatic color. Both are pelleted for easy, precise sowing.
12. Petchoa — The Hybrid That Does It All
Best for: Zones 8-11 (direct sow or transplant in September); Zones 6-7 (start indoors)
Petchoa is the exciting hybrid cross between petunia and calibrachoa — combining the large, showy blooms of petunias with the weather-toughness and prolific flowering of calibrachoa. The result is a plant that performs beautifully in containers, hanging baskets, and garden beds with minimal fuss.
Our Petchoa Caliburst Nectarine is a stunning new variety with warm, peachy-nectarine blooms that glow in the fall garden.
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September Planting Tips for Success
- Know your last frost date. In cooler zones, September planting is all about timing relative to your first fall frost.
- Use pelleted seeds for precision. Pelleted seeds are coated for easier handling — especially important for tiny seeds like lisianthus, snapdragons, and violas.
- Start cool-season flowers early in the month. In Zones 5-7, aim to get seeds in the ground or started indoors in the first two weeks of September.
- Warm-zone gardeners: embrace the season shift. In Zones 9-11, September is the beginning of your best growing season. Take full advantage by planting generously.
- Use grow lights for indoor starts. Natural light alone is rarely sufficient as days shorten in fall.
- Water consistently but don't overwater. Seedlings need consistent moisture but excellent drainage. Overwatering in cooler temperatures is a common cause of damping off.
Related Growing Guides
- Snapdragon Seeds: The Complete Guide to Growing Premium Cut Flowers From Seed
- Lisianthus Seeds: The Complete Guide to Growing Premium Cut Flowers From Seed
- Zinnia Seeds: The Ultimate Guide to Growing the Best Cut Flowers
- African Marigold Seeds Growing Guide | Giant Marigold Flowers
- A Simple Guide to Growing Vibrant Flowers from Seeds at Home
Frequently Asked Questions: September Planting by Zone
What can I plant in September in Zone 3-4?
In Zones 3-4, September is your last chance to direct sow cold-hardy annuals like violas and snapdragons before frost. Focus on starting seeds indoors for overwintering or spring transplants. Hardy violas can handle light frost and are excellent for fall color.
What flowers can I plant in September in Zone 5-6?
Zones 5-6 gardeners can plant snapdragons, violas, marigolds for late bloom, and start lisianthus seeds indoors in September for spring transplants. Pansies and violas thrive in the cooling temperatures of fall in these zones.
What should I plant in September in Zone 7-8?
Zone 7-8 gardeners have a fantastic September planting window. Direct sow snapdragons, violas, stock, zinnias for late bloom, and start lisianthus, gerbera daisy, and cineraria seeds indoors. Fall is prime planting season in these zones.
What can I plant in September in Zone 9-10?
September is the start of the main growing season in Zones 9-10. Plant snapdragons, lisianthus, gerbera daisies, pentas, vinca, zinnias, marigolds, sunflowers, and more. The cooling temperatures make September ideal for establishing cool-season flowers.
Can I start lisianthus seeds in September?
Yes! September is an excellent time to start lisianthus seeds indoors in most zones. Lisianthus requires a long growing period of 5-6 months to bloom, so starting in September sets you up for stunning spring and early summer cut flowers.
Are snapdragons good for fall planting?
Absolutely. Snapdragons are one of the best flowers to plant in September. They thrive in cool weather, tolerate light frost, and produce stunning cut flowers. In Zones 7-10, they can be direct sown or transplanted in September for fall and winter blooms.
What is the easiest flower to start from seed in September?
Zinnias, marigolds, and sunflowers are among the easiest flowers to start from seed in September in warmer zones (8-10). For cooler zones, violas and snapdragons are reliable and forgiving for beginner seed starters.
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Happy planting! September is one of the most rewarding months to be a gardener — no matter your zone, there's something beautiful waiting to grow. Shop our full collection of premium pelleted flower seeds at Trailing Petunia and get growing today.
Also visit our bulk seeds sister site: Trailing Petunia Bulk Seeds for larger quantity orders.