B) Cool forcing / finishing in an unheated cold house (SOP)
Cooler, more natural cycle – compact, hardened plants with lower energy demand
The aim of the cold house (cool) finishing route is not “as fast as possible”, but a compact habit, good stress tolerance and lower energy input. The key points: cool but frost-free conditions, good ventilation, under‑irrigation, and avoiding “wet plants” (especially before despatch and packing).
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In short Objective & risk B1 Planting (immediately) B2 Climate & ventilation B3 Pruning & pinching B4 Irrigation & feeding B5 Crop protection (IPM) B6 Despatch window “Send out dry” Common mistakes Why is it an advantage?
In short – cold-house route in 10 points
- Immediate potting: pot straight into the final container on arrival – do not leave semi-finished material standing for days.
- Storage (if unavoidable): only in cool and light; dark storage reduces quality and increases Botrytis risk.
- Planting depth: in a cool cycle usually 3–4 cm deeper than the original tray level (stability).
- Substrate: peat-based, coarser structure with reliable drainage.
- Climate: cool–light–frost‑free; too much heat = stretching.
- Temperature limits (day+night average): work with “maximum average” values per period.
- Irrigation: preferably from below (ebb and flow/capillary/dripper); overhead irrigation should be avoided.
- Pruning: “real” cut-back after c. 4 weeks (target: c. 10 cm), then pinching at 5 leaves on dominant shoots.
- IPM: prevention = dry foliage + air exchange + hygiene; not every product works the same in the cold.
- Despatch: it is advisable to despatch flowering, finished batches – “send out dry”.
Related: “Send out dry” → Irrigation principles →
PHARMAROSA® NEONATAL
Cool forcing / finishing in an unheated cold house – scheduling table (indicative 10–12 weeks; cool, light, frost‑free)
| Stage / operation | 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 |
| Receipt → immediate planting into the final sales pot + watering‑in (preferably from below) | ◆ | | | | | | | | | | |
| Planting 3–4 cm deeper (stable stand) + well‑drained, coarser-structured substrate | ◆ | | | | | | | | | | |
| Cool–light–frost‑free conditions + frequent, gentle air exchange (dehumidification, leaf drying) | ■ | ■ | ■ | ■ | ■ | ■ | ■ | ■ | ■ | ■ | ■ |
| Plant spacing: tight start → early spacing once canopies close (to reduce humidity and fungal pressure) | | | ◆ | ◆ | | | | | | | |
| Real cut-back c. 4 weeks after potting (guideline: ~10 cm above the compost surface) | | | | | ◆ | | | | | | |
| Pinching of strong basal shoots 2–3 weeks later (standard: pinch at the first 5 leaves) | | | | | | | ◆ | ◆ | | | |
| Irrigation & nutrition: under‑irrigation + stable management (pH/EC targets depending on measurements) | ■ | ■ | ■ | ■ | ■ | ■ | ■ | ■ | ■ | ■ | ■ |
| Crop protection principle: Botrytis prevention (leaf drying, air exchange, hygiene, IPM monitoring) | ■ | ■ | ■ | ■ | ■ | ■ | ■ | ■ | ■ | ■ | ■ |
| Finishing / flowering (temperature- and light‑dependent; in a cool rhythm it can take longer) | | | | | | | | ■ | ■ | ■ | ■ |
| Hardening / preparing for transport + “send out dry” (reducing packing risk) | | | | | | | | | | ■ | ■ |
| Saleability / despatch | | | | | | | | | | | ◆ |
◆ = one‑off operation / milestone
■ = continuous phase in the given weeks
Temperature guidelines (average day+night, reference values): up to 1 March 8–10 °C; 1 March–1 April: 12–14 °C; 1 April–1 May: 15–16 °C; after 1 May: 16–17 °C. In a cool cycle, the key is rapid leaf drying and frequent, gentle air exchange. Irrigation preferably from below; overhead irrigation should be avoided. Transport always in a dry state.
Objective & risk points (in the cold house)
- Objective: compact, hardened plants, a stable spring despatch window, lower energy input.
- Main risk: humid pockets and slow leaf drying → Botrytis; secondary: stretching at too high a temperature.
- Quality criteria: uniform bush shape, clean foliage, stable substrate, batch can be packed in a dry state.
B1) Immediate planting into the sales pot after receipt
Basic rule
- NEONATAL material must not stand unprocessed for days. Plant immediately or within a very short time.
- If there is a delay: cool + light; dark storage must be avoided.
Planting depth (cold-house logic)
- Guideline: c. 3–4 cm deeper than the level in the original tray.
- Reason: more stable stand, “no wobble”, better framework building.
- Important: do not bury petioles or leaves.
Pot size & plants per pot (starting standard)
| Pot size | NEONATAL / pot (guideline) | Comment |
| 2 litre | 2 pcs | Fast, compact; batch uniformity is key |
| 3 litre | 3 pcs | Fuller stand, stable on‑bench appearance |
| 6 litre | 4 pcs | Premium appearance, strong bush |
Substrate quality
- Peat‑based, coarser structure → reliable drainage and aeration.
- There is no universal recipe: it must be fine‑tuned to water quality and the irrigation system.
Details: Pot size & plants per pot → Substrate, pH, EC →
B2) Cool–light–frost‑free conditions, ventilation regime
In a cold house, the aim is to keep temperatures down to achieve compact growth, while maintaining frost‑free conditions and fast leaf drying. Excessive heat results in rapid stretching and softer tissues.
Indicative maximum average temperature (day+night)
| Period | Recommended maximum average temperature |
| Until 1 March | 8–10 °C |
| 1 March – 1 April | 12–14 °C |
| 1 April – 1 May | 15–16 °C |
| After 1 May | 16–17 °C |
Ventilation
- Frequent, gentle air exchange → humidity should not build up, foliage must dry quickly.
- Earlier spacing once the canopy is closing.
Frost protection in an unheated system
- Fleece/agrifabric for cold nights.
- Short periods of slight cooling may occur, but in stronger cold spells covering is essential.
B3) Pruning & pinching schedule (in a cool cycle)
In a cool cycle plants respond more slowly, therefore well‑timed interventions are key to a uniform bush shape. Objective: round, compact plants – not rapid stretching.
Cut-back (guideline)
- Timing: c. 4 weeks after potting (depending on development stage).
- Height: guideline ~10 cm above the substrate surface.
- Several plants per pot: identical cutting height is essential – otherwise dominance and one‑sided plants occur.
Pinching (dominant basal shoots)
- Strong basal shoots often appear 2–3 weeks later.
- Proven method: pinch at the first 5 leaves (counted from the shoot tip).
Details: Pruning & pinching management →
B4) Irrigation (preferably from below) and nutrient management
Irrigation – preference: from below
- Best option: ebb and flow benches.
- Alternative: capillary bed/mat or dripper to every pot.
- Overhead irrigation should be avoided: long leaf‑wetness periods → high fungal risk.
Rhythm
- No fixed calendar: weather and substrate decide.
- Basic principle: do not let it dry out completely, but avoid prolonged wetness (lack of air = risk).
pH/EC targets (if measured)
- Substrate pH: about 5.3–5.8; irrigation solution pH: about 5.5–5.8 (guideline values).
- EC logic: cool / less frequent irrigation → higher EC can work; warm / frequent irrigation → lower EC is better.
More details: Irrigation → Substrate, pH, EC →
B5) Crop protection principles in a cool environment (IPM)
- No universal spray calendar: interventions as required, based on monitoring.
- Effectiveness rule in the cold: not every solution works at low temperatures → product choice must reflect this.
- Most frequent climate‑related risk: Botrytis → prevention: leaf drying, air exchange, hygiene, under‑irrigation.
General principles: IPM & sustainability →
B6) Saleability / despatch window
With the cold-house route the target is typically to supply the spring market with compact, flowering finished plants. The batch should be ready and stable – it is generally not advisable to “hold, cut back and re‑grow for later”, as this may reduce quality.
Time requirement (guideline, temperature‑dependent)
- Early spring: finishing often takes 8–10 weeks (after pinching).
- Later (May–June): 6–8 weeks is often sufficient.
- Total throughput: indicatively ~10–12 weeks from receipt to finished product.
Despatch: “send out dry” (especially from cold houses)
- Finished batches should be transported in a dry state (foliage and crop should not be wet).
- Timing of the last irrigation: substrate must not be dripping at loading.
- If there is a waiting period: cool, light, well‑ventilated conditions.
Detailed protocol: “Send out dry” →
Common mistakes (quick troubleshooting)
- Stretching: temperature too high → more aggressive ventilation and keeping temperature down.
- Botrytis foci: humid patches → hygiene + air exchange + isolation, strict under‑irrigation.
- Wet despatch: poor irrigation timing → adjust water management before despatch.
- Dark storage: quality decline → only cool–light storage for short periods.
Why is the cold-house route an advantage for the buyer?
- Compact, hardened plants: better stress tolerance at planting and along the supply chain.
- Lower energy input: more natural cycle, stable cost base.
- Stable spring despatch: more predictable timing.
- Own‑root advantage: simpler structure, fewer risk points – more stable branching and regeneration.
Would you like to discuss your starting settings for the cold-house route?
We briefly review your target product, plants per pot, a climate routine matching your temperature limits, the under‑irrigation system and the pruning & pinching timeline, tailored to your cold house.
Request a consultation Or write to us directly: [email protected]
PharmaRosa® NEONATAL – B) Cold-house route
Compact, hardened plants – with a cool, stable production regime.