Most beginner grows don't fail at germination — they fail during the transplant. Roots snap, plants sit for a week refusing to grow, or the entire tray wilts overnight. The fix is a repeatable process, not luck.
When to transplant
Wait until seedlings have 2–3 true leaves (not the initial cotyledons) and roots poke through the bottom of the starter cube. Rushing past this stage is the single biggest cause of transplant failure.
Pre-transplant checklist
- Reservoir pH: 5.8–6.2
- Starter EC: 0.8–1.0 mS/cm (roughly half strength)
- Water temp: 18–22 °C
- Lights: dimmed to ~50 % for 48 hours after transplant
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The transplant, step by step
- Soak the starter cube in plain pH-adjusted water for 5 minutes to hydrate the roots.
- Nest the cube in the net cup — don't force it. If it's a tight fit, use a slightly larger net cup rather than crushing roots.
- Backfill with clay pebbles up to the base of the stem. Avoid burying the stem itself.
- Lower into reservoir so water touches the bottom 1 cm of the cube but not the pebbles.
- Dim the lights for 2 days. This one step alone prevents 80 % of transplant wilting.
- Raise EC to full strength after 5–7 days once new growth is visible.
What to do if it wilts anyway
Cover the plant with a clear cup or dome for 24 hours to raise humidity. Nine out of ten "dead" transplants recover overnight.
Transplant supplies we keep on the bench
Last checked: 2026-07-05 · affiliate disclosure
| Product | Role | Reusable? | Where | |
|---|---|---|---|---|
Grodan Rockwool Starter Cubes Start here | $15 | Germination + transplant medium | No — one grow | Check price |
Hydroton Clay Pebbles | $20 | Net-cup fill around the cube | Yes — rinse in peroxide | Check price |
2-inch Net Pots (50-pack) | $12 / 50 | Holds cube + pebbles in the reservoir lid | Yes | Check price |
Combo pH + EC Pen | $15 | Check pH 5.8–6.2 and EC 0.8–1.0 before transplant | 1–2 years | Check price |
General Hydroponics pH Up & Down Kit | $20 | Adjust reservoir pH into the safe window | Years per bottle pair | Check price |
- Price
- $15
- Role
- Germination + transplant medium
- Reusable?
- No — one grow
- Price
- $20
- Role
- Net-cup fill around the cube
- Reusable?
- Yes — rinse in peroxide
- Price
- $12 / 50
- Role
- Holds cube + pebbles in the reservoir lid
- Reusable?
- Yes
- Price
- $15
- Role
- Check pH 5.8–6.2 and EC 0.8–1.0 before transplant
- Reusable?
- 1–2 years
- Price
- $20
- Role
- Adjust reservoir pH into the safe window
- Reusable?
- Years per bottle pair
Related: Hydroponics for Beginners · pH and EC for Beginners · 10 Common Hydroponic Mistakes · The Kratky Method Explained · How to Clean Your Hydroponic System
Frequently asked questions
Can I transplant soil-grown seedlings into hydroponics?
Yes — rinse the roots thoroughly under lukewarm water to remove every trace of soil, then follow the transplant steps. Expect a slightly longer settling period.
Why do my seedlings wilt right after transplant?
Almost always light shock or root shock. Dim the lights for 48 hours and cover the plant with a humidity dome. Full recovery is normal within a day.
How long until I see new growth after transplant?
5–7 days is typical. If nothing has moved in 10 days, check reservoir temperature — cold water below 16 °C stalls root growth completely.
When should you transplant seedlings into a hydroponic system?
Wait until seedlings have 2–3 true leaves (not the initial cotyledons) and roots poke through the bottom of the starter cube. Transplanting earlier is the single biggest cause of failure.
What EC and pH should you use for freshly transplanted seedlings?
Start at pH 5.8–6.2 and EC 0.8–1.0 mS/cm — about half strength. Raise to full strength after 5–7 days once new growth appears.
Should you dim grow lights after transplanting?
Yes. Dim to roughly 50% for 48 hours after transplant. This single step prevents about 80% of transplant wilting.
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