Running a cut flower operation means one thing above all else: you need blooms ready when your customers want them — not two weeks early, not a week late. For greenhouse growers, that precision comes from succession planting: staggering your seed starts so you're harvesting continuously rather than all at once.
This month-by-month greenhouse succession planting calendar is built for commercial cut flower growers, market farmers, and floral wholesalers who rely on a steady, predictable harvest window. Whether you're supplying florists, farmers markets, or a CSA flower subscription, this guide will help you plan your seed starts, manage bench space, and keep your cooler stocked from late winter through hard frost.
Bookmark this page. Come back to it every month. Your future self — the one with a full cooler and happy wholesale accounts — will thank you.
Home gardeners can find smaller packs at trailingpetunia.com.
Why Succession Planting Is Non-Negotiable for Cut Flower Growers
A single planting of zinnias, for example, will give you a flush of blooms over roughly three to four weeks. After that, the plants slow down, stems get shorter, and quality drops. If you planted everything at once, you're scrambling to fill orders during the gap.
Succession planting solves this by staggering starts every two to three weeks so that as one planting peaks, the next is just coming into its prime. The result is a rolling harvest that extends your season by weeks — sometimes months — and keeps your revenue consistent.
In a greenhouse, you have even more control. You're not at the mercy of last frost dates for your starts. You can push earlier, extend later, and dial in timing with precision that field-only growers simply can't match.
How to Use This Calendar
This calendar assumes you have a heated greenhouse capable of maintaining 60–70°F nights and 70–80°F days during germination. Adjust timing by two to three weeks earlier or later depending on your zone, your target market dates, and your specific greenhouse conditions.
Each month includes:
- What to start — crops suited to that timing window
- Succession interval — how often to re-sow for continuous harvest
- Notes for commercial growers — variety tips, spacing, and harvest timing
Month-by-Month Greenhouse Seed Starting Calendar
January – Early Season Push
Goal: Get your first wave of cool-season crops started and plan your warm-season succession schedule.
January starts are all about cool-tolerant crops that can handle the lower light levels of midwinter. Focus on crops that will be ready for late March and April markets.
What to start:
- Snapdragons (10–12 weeks to harvest)
- Lisianthus (16–20 weeks — start now for June harvest)
- Stock
- Ranunculus (if overwintering in greenhouse)
Succession interval: Every 3 weeks for snapdragons; lisianthus is a single long-season start.
Grower notes: Lisianthus is notoriously slow and fussy at germination. Use a heat mat set to 75°F and expect 2–3 weeks to emergence. Don't rush transplanting — they need 6–8 true leaves before moving to the bench.
February – Warm-Season Succession Begins
Goal: Start your first wave of warm-season crops and continue cool-season succession.
February is when the real succession planning kicks in. You're now starting crops that will hit peak harvest in May and June — prime time for weddings, Mother's Day, and spring markets.
What to start:
- Zinnias (first succession — 8–10 weeks to harvest in greenhouse)
- Sunflowers (first succession — 6–8 weeks)
- Celosia
- Gomphrena
Succession interval: Every 2–3 weeks for zinnias and sunflowers.
Grower notes: For cut flower zinnias, the Zinnia Sun Formula Mix is a reliable commercial performer with long, strong stems and excellent vase life. Start in 72-cell trays and transplant at 3–4 true leaves. Don't direct sow in the greenhouse — transplants establish faster and give you better spacing control.
For sunflowers, the Pro Cut Bicolor DMR is a pollen-free cut flower variety that won't stain arrangements — a must for wholesale accounts.
March – Peak Succession Window
Goal: Maintain 2–3-week succession intervals on all warm-season crops; harden off cool-season transplants.
March is your busiest seed-starting month. You're juggling multiple crops at different stages, hardening off your January and February starts, and ramping up bench space.
What to start:
- Zinnias (second and third succession)
- Sunflowers (second succession)
- Cosmos
- Marigolds (for filler and dried flower programs)
Succession interval: Every 2 weeks for zinnias; every 3 weeks for sunflowers.
Grower notes: Cosmos are fast — 6–8 weeks from seed to harvest — and they're a high-value filler that florists love. They also self-regulate spacing well in the field, making them low-maintenance once established.
For a deeper look at building a multi-crop cut flower program, see our post on Best Bulk Cut Flower Seeds to Grow Featuring Lisianthus, Zinnias & More.
April – Transition to Field Production
Goal: Begin transitioning greenhouse starts to field or high tunnel; continue succession starts for summer harvest.
By April, your greenhouse is likely at capacity. This is the month to start moving your hardened-off transplants to the field or high tunnel and free up bench space for the next succession wave.
What to start:
- Zinnias (fourth succession — targeting July/August harvest)
- Sunflowers (third succession)
- Gomphrena (for dried flower program)
- Strawflowers
Succession interval: Every 2–3 weeks.
Grower notes: Zinnia Dreamland Mix is an excellent compact variety for high tunnel production where height control matters. Pair it with taller Zinnia Sun series varieties in the open field for a full range of stem lengths.
For tips on building a pollinator-friendly cut flower farm that also supports your local ecosystem, check out How to Grow a Pollinator Paradise with Bulk Flower Seeds.
May – Summer Succession in Full Swing
Goal: Keep succession intervals tight; monitor for heat stress in the greenhouse.
May brings rising temperatures that can stress seedlings in an unventilated greenhouse. Shade cloth, roll-up sides, and active ventilation become critical. Focus on heat-tolerant crops for your summer succession.
What to start:
- Zinnias (fifth succession — targeting August/September harvest)
- Sunflowers (fourth succession)
- Celosia (excellent heat tolerance)
Succession interval: Every 2 weeks.
Grower notes: Celosia is one of the most heat-tolerant cut flowers you can grow and one of the most profitable per stem. It also dries beautifully, giving you a secondary revenue stream in your dried flower program. Start in 72-cell trays and transplant at 3–4 true leaves.
For a broader look at summer planting strategy, see The Best Bulk Flower Seeds to Plant This Summer for Vibrant Blooms.
June – Midsummer Starts for Fall Harvest
Goal: Start your fall succession crops; evaluate mid-season performance and adjust intervals.
June starts are your bridge to fall markets — harvest festivals, fall weddings, and the September/October farmers market surge. Don't skip this window. Growers who stop starting seeds in June often find themselves with an empty cooler in September.
What to start:
- Zinnias (sixth succession — targeting September/October harvest)
- Sunflowers (fifth succession)
- Gomphrena (long-season filler for fall)
Succession interval: Every 2–3 weeks.
Grower notes: The Sunflower Pro Cut Gold Lite DMR is a pollen-free, single-stem variety that performs exceptionally well in summer heat and produces clean, market-ready stems through October.
July – Last Call for Warm-Season Crops
Goal: Make your final warm-season succession starts; begin planning for cool-season fall crops.
July is your last reliable window for warm-season crops in most zones. Anything started after mid-July risks running out of season before it reaches harvest maturity — unless you're in Zone 9 or 10, or you have a heated greenhouse to extend into fall.
What to start:
- Zinnias (final succession — Zones 7–10 only)
- Sunflowers (final succession)
- Strawflowers (for dried flower program)
Succession interval: Final start — no further succession needed.
Grower notes: This is also the month to audit your bulk seed inventory. What ran out faster than expected? What did you over-order? Use this data to refine your succession plan for next year. Buying in bulk — 1,000-seed packs — gives you the flexibility to run multiple successions without running short mid-season. See our guide on Buying Bulk Seeds To Grow Many Cut Flower Varieties for more on building a smart seed inventory.
August – Cool-Season Transition
Goal: Shift greenhouse focus to cool-season crops for fall and early winter harvest.
August is the pivot month. Warm-season crops are winding down in the greenhouse, and it's time to start thinking about what will fill your cooler in October and November.
What to start:
- Snapdragons (for October/November harvest)
- Stock
- Lisianthus (for late winter/early spring — long lead time)
Succession interval: Every 3 weeks for snapdragons.
Grower notes: Cool-season crops need to be established before temperatures drop below 50°F at night. Get your snapdragon starts in by mid-August to ensure they're well-rooted before fall sets in.
September Through December – Greenhouse-Only Production
Goal: Maintain heated greenhouse production for winter markets; plan next year's succession calendar.
For growers with heated greenhouses, September through December is an opportunity to serve florists and event planners who struggle to source locally grown flowers in winter. Snapdragons, stock, and ranunculus can all be harvested through the winter months with proper heat and supplemental lighting.
Use the slower pace of winter to review your succession records, refine your variety selection, and place your bulk seed orders for next year. Early ordering ensures you get the varieties you want — popular cut flower varieties like the Zinnia Sun Cherry and Sunflower Sunfinity Hybrid sell out fast.
Succession Planting Quick-Reference Table
| Crop | Weeks to Harvest | Succession Interval | Best Start Months |
|---|---|---|---|
| Zinnia (cut flower) | 8–10 weeks | Every 2–3 weeks | Feb–July |
| Sunflower (single stem) | 6–8 weeks | Every 2–3 weeks | Feb–July |
| Lisianthus | 16–20 weeks | Single start | Jan, Aug |
| Snapdragon | 10–12 weeks | Every 3 weeks | Jan, Aug–Sep |
| Celosia | 10–12 weeks | Every 3 weeks | Mar–May |
| Cosmos | 6–8 weeks | Every 2–3 weeks | Mar–May |
| Gomphrena | 12–14 weeks | Every 3–4 weeks | Feb–June |
| Strawflower | 10–12 weeks | Every 3 weeks | Apr–July |
| Stock | 10–14 weeks | Every 3 weeks | Jan, Aug |
Related Posts
- Best Bulk Cut Flower Seeds to Grow Featuring Lisianthus, Zinnias & More
- Buying Bulk Seeds To Grow Many Cut Flower Varieties
- How to Grow a Pollinator Paradise with Bulk Flower Seeds
- The Best Bulk Flower Seeds to Plant This Summer for Vibrant Blooms
- Cool-Weather Color and Sun-Kissed Texture: Planting Lobelia and Strawflowers from Seed
FAQ
How many successions of zinnias should I plant per season?
Most commercial cut flower growers run 5–7 successions of zinnias from February through July, with each succession spaced 2–3 weeks apart. This produces a continuous harvest from May through October. The exact number depends on your market demand, bench space, and zone.
Can I succession plant in a cold greenhouse or high tunnel?
Yes, but your start dates will shift. A cold greenhouse (unheated, frost-protected) extends your season by 4–6 weeks on each end compared to field production, but you won't be able to start as early as a heated greenhouse. Focus on cold-tolerant crops like snapdragons, stock, and ranunculus for early and late-season production.
What's the best cut flower for a beginner succession planting program?
Zinnias are the go-to starting point. They germinate quickly (3–5 days at 75°F), grow fast, and are forgiving of minor timing errors. They also have strong market demand and excellent vase life. Start with a reliable cut flower variety like the Zinnia Sun series and add crops as you gain confidence.
How do I track my succession planting schedule?
A simple spreadsheet works well. Track start date, crop, variety, tray count, transplant date, and expected harvest window for each succession. Color-code by harvest month so you can see at a glance whether you have gaps. Review it weekly during peak season.
When should I stop starting seeds for the season?
For warm-season crops, your cutoff is typically 8–10 weeks before your first expected frost date (for zinnias and sunflowers). For cool-season crops in a heated greenhouse, you can continue starting through August and September for fall and winter harvest.
How much seed do I need for a succession planting program?
Plan on 1,000-seed packs as your base unit. A single 1,000-seed pack of zinnias, started in 72-cell trays with 90% germination, gives you roughly 900 transplants — enough for a 100-foot bed at 9-inch spacing. For 6 successions, you'll need 4–6 packs depending on your planting density and germination rate.
Does succession planting work for dried flowers too?
Absolutely. Crops like gomphrena, strawflowers, and celosia benefit from succession planting just as much as fresh-cut crops. Staggering your starts means you're harvesting at peak dryness throughout the season rather than processing a massive batch all at once.