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Created article Getting Scion and Rootstock Timing Right for Greenhouse Tomatoes
Created article Getting Scion and Rootstock Timing Right for Greenhouse Tomatoes
by Paramount Seeds on Sep 01 2026
Why Timing Matters
Grafting relies on rootstock and scion reaching the same stem diameter (1.5–2.5mm) at the same time. Most rootstocks are more vigorous than scions, so if seeded together, the rootstock will be too thick by the time the scion is ready. The fix: seed the scion first.
Seeding Offset by Rootstock
Seed your scion 2–4 days before the rootstock under standard conditions (22–25°C day / 18–20°C night):
- Maxifort F1 / DR0141TX F1: Highly vigorous — seed scion 3–4 days earlier
- Multifort F1 / Estamino F1: Moderate vigour — seed scion 2–3 days earlier
Treat these as starting points. Measure stem diameter from day 10 and adjust your offset for the next cycle based on what you observe.
Planning Your Schedule
- Set your target graft date (work backwards from transplant, allowing 7–10 days post-graft for healing).
- Most rootstocks hit graft-ready stage in 10–14 days from germination.
- Seed scion 2–4 days before rootstock per the table above.
- Monitor stem diameter daily from day 10 — don't rely on calendar days alone.
- For large volumes, seed rootstock in two batches 2 days apart to widen your grafting window.
When Timing Goes Wrong
- Rootstock too thick: Drop night temp 2–3°C and reduce watering slightly.
- Scion too thick: Graft early if mismatch is <0.5mm; otherwise adjust offset for next batch.
- Both too thin: Raise day temp 1–2°C and check light levels — thin stems usually mean insufficient DLI.
Grafting Method & Diameter Tolerance
- Cleft grafting: Most forgiving — up to 0.5mm mismatch acceptable.
- Clip grafting: Aim for within 0.3mm.
- Tube grafting: Least tolerant — diameters must closely match.
See our step-by-step grafting guide for full technique details.
Environmental Adjustments
- Low light / winter: Extend offset 1–2 days or add supplemental lighting.
- High summer temps: Reduce offset by 1 day; monitor more frequently.
- Over-wet substrate: Slows stem thickening — keep at 60–70% field capacity. See our guide on growing media moisture management.
- Primed seed: Primed seed germinates more uniformly and may slightly compress the days-to-graft window.
After Grafting: Next Steps
Once your graft has healed and plants are established, review our guides on pruning indeterminate tomatoes, plant spacing, and pollination to carry your crop through to harvest.
Choosing the Right Rootstock
Timing is only part of the equation. See our rootstock selection guide, rootstock varieties comparison, and deep-dive on Maxifort vs DR0141TX to select the best match for your system.
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