Why Continuous Production Is a Scheduling Problem, Not a Growing Problem
A farm can grow excellent lettuce and still miss a standing order every week, because supply comes in waves. Three bays planted on the same day mature on the same day, the packing line is overwhelmed on Tuesday and idle on Friday, and the buyer notices the variability long before the grower does.
Continuous supply is produced by a calendar, not by good intentions. This guide covers how to build one: work backwards from harvest, size batches to your weekly commitment, build in propagation lead time and a contingency margin, and level the labour rather than the ambition.
Work Backwards From the Delivery Date
- Start at the committed delivery date and subtract harvest and packing time, grow-out time, transplant handling, and propagation time
- Add a buffer at each stage rather than one large buffer at the end; small buffers absorb realistic variation, one big buffer hides slippage until it is too late to fix
- Account for seasonal variation in cycle time. A 35-day summer lettuce crop can be 55–60 days in a low-light winter unless you add light or heat
- Set the seeding day and write it in the calendar as a fixed commitment with an owner
- Plan the propagation capacity from the seeding schedule, not the other way round
Cycle Times by Crop and Season
| Crop | Propagation | Grow-out, summer | Grow-out, winter | Notes |
|---|---|---|---|---|
| Butterhead lettuce | 14–21 days | 28–35 days | 45–60 days | Most seasonal-sensitive common crop |
| Crisphead / iceberg | 18–24 days | 45–55 days | 65–80 days | Plan winter cycles carefully; head fill stalls in low light |
| Baby leaf | Direct seeded | 21–28 days | 30–45 days | Multiple cuts possible on some species |
| Spinach | Direct or 14 days | 28–35 days | 40–55 days | Bolting risk in long hot days; shade or variety selection |
| Basil | 14–21 days | 28–35 days | 45–60 days | Cut-and-come-again; needs warmth year-round |
| Coriander / cilantro | Direct seeded | 25–35 days | 35–50 days | Succession plant every 10–14 days for steady supply |
| Microgreens | None | 7–14 days | 10–18 days | Shortest cycle; scheduling is a daily discipline |
| Strawberry | Plug plants | 60–90 days to first fruit | 90–120 days | Long production window once established |
| Tomato | 21–28 days | 60–80 days to first pick | 80–100 days | Continuous harvest over many months |
Batch Sizing: Match the Harvest to the Commitment
The most common scheduling error is planting in convenient round numbers instead of in the quantity the market needs. Batch size follows from the weekly commitment and the expected pack-out.
| Step | Calculation | Example |
|---|---|---|
| Weekly commitment | From the supply agreement | 2,000 kg/week of packed lettuce |
| Pack-out rate | Saleable ÷ harvested | 90% |
| Required harvest | Commitment ÷ pack-out | 2,222 kg harvested/week |
| Yield per plant | From your historical average | 0.22 kg |
| Plants to transplant | Harvest ÷ yield per plant | 10,100 plants/week |
| Transplant loss allowance | Historical establishment rate | 4% loss → 10,520 plants |
| Propagation requirement | Plants ÷ germination and cull rate | At 92% → 11,435 plugs/week |
Then divide that batch into as many weekly blocks as your cycle allows, so that every week has a block at each growth stage. A 35-day crop with weekly planting runs five blocks simultaneously: propagation, week 1, week 2, week 3, and harvest. That is what produces a flat harvest profile.
Levelling Labour, Not Just Volume
- Plot labour by week, not just kg by week. Transplanting and harvesting are the two peaks; if both land in the same week, you will be short-handed every time
- Stagger the blocks by a few days if a single weekly block overloads one day
- Keep propagation on a fixed weekday so nursery work becomes routine rather than reactive
- Reserve maintenance windows. A calendar with no slack will eventually skip the annual service
- Plan around holidays and peak demand weeks — retail orders often rise 20–40% around holidays, and your calendar should build stock in advance
Contingency: Plan for a Bad Week
| Risk | Calendar response |
|---|---|
| Crop loss in one block | Hold 5–10% spare production capacity, or a fast-turn short-cycle crop as a filler |
| Seasonal cycle stretch | Add days to the winter plan from historical data, not from the seed catalogue |
| Propagation failure | Seed 5–8% above requirement and keep a rolling spare plug batch |
| Labour absence at peak | Cross-train and keep one flexible block that can be moved a week |
| Equipment downtime | Do not schedule 100% of growing area at once; keep a serviceable fraction free |
| Demand spike | Agree an uplift mechanism with the buyer in advance, including notice period |
Keeping the Calendar Honest
- Record actual against planned for every block: transplant date, harvest date, harvested kg, pack-out
- Re-baseline cycle times seasonally. The calendar built in June will be wrong in December if you do not update it
- Review the plan monthly and re-phase any block that has drifted, rather than accepting the slip
- Keep one version. A calendar in three spreadsheets is not a calendar
- Link it to the KPI pack. Plan attainment is only meaningful if the plan is written down first — see our crop production guide for the agronomic inputs behind each block
FAQ
How far ahead should a hydroponic planting calendar be set?
At least one full crop cycle plus propagation lead time — typically eight to twelve weeks for leafy greens, and a full season for fruiting crops. Review it monthly and re-baseline cycle times at each season change.
How do I size each planting batch?
Work from the weekly supply commitment: divide by pack-out rate to get required harvest, divide by yield per plant to get plants, then add transplant loss and propagation loss allowances to get the seeding quantity.
Why does my harvest come in waves?
Blocks planted on the same day mature on the same day. Split each batch into weekly blocks so that every week has plants at each growth stage, which produces a flat weekly harvest profile.
How much extra should I seed as a buffer?
Five to eight percent above the transplant requirement is typical, covering germination variability, culling and transplant losses. Track your actual establishment rate and refine the figure each quarter.
How do seasonal changes affect the calendar?
Low light and cooler root zones lengthen cycles substantially — a 35-day summer lettuce crop can run 55–60 days in winter. Build winter cycle times from your own historical data and re-baseline the calendar seasonally.
Should I keep spare capacity?
Yes. Holding 5–10% of growing area unscheduled gives you somewhere to put a replacement block after a loss and space to service equipment without stopping production.
Get a Planting Calendar Built Around Your Commitment
Send your weekly volume commitment, crop mix, system layout and climate data through the quote form. We will return a phased planting calendar with batch sizes, propagation capacity requirements and a labour profile by week.