Cloning Environment & Venting Plan
The dome transition is where healthy rooted clones die. Enter your propagation method and stick date to get environment targets for the propagation phase, a day-by-day dome venting schedule keyed to when your first roots appear, and the estimated date clones are ready for open-air conditions. Companion to the Rooting Timeline Tracker.
Build your dome venting schedule
Match this to your propagation method and temperature. Use the Rooting Timeline Tracker for personalized first-roots dates.
Override with actual root date
If you've already observed first roots, switch the offset above to match the actual day. The venting schedule updates to calendar dates from that real observation point.
Environment for this method
—
Select a propagation method.
Common dome venting mistakes
- Removing the dome before roots appear. The dome's job is to replace the humidity the clone's roots would otherwise provide. Before roots form, the clone cannot take up water — remove the dome and the leaves desiccate within hours. Venting starts at first roots, not at a fixed day count.
- Going from sealed to fully open in one step. Stomata (leaf pores) need time to adjust to regulating moisture loss. Sudden full dome removal after days of 90%+ RH causes wilt even in well-rooted clones. The 8-day progressive protocol exists specifically to avoid this.
- Misting the leaves directly. Mist the dome walls, not the leaves. Direct leaf misting promotes powdery mildew and can clog stomata. Condensation on dome walls indicates adequate humidity without directly wetting plant tissue.
- High PPFD during propagation. Clones don't need strong light — they need just enough for minimal photosynthesis while directing energy to root production. T5 or a dimmed LED at 24–36" is ideal. High-intensity veg lighting applied to rootless cuttings causes stress without benefit.
Venting starts
—
Dome fully off
—
Environment targets
DOME TEMP
—
DOME RH
—
PPFD
—
DOME VPD
—
POST-DOME VPD
—
—
Venting schedule
The dome venting protocol — four stages
Set method and stick date — get your venting start date
Select your propagation method and the day you stuck cuttings. The "first roots expected" offset defaults to method-appropriate timing — adjust it down if your clones root faster than typical, or up if conditions are suboptimal. The venting start date is the anchor for the entire schedule. If you've already observed actual first roots, switch the offset to match the real day observed rather than the estimated one.
Maintain dome environment through Phase 1
Before venting starts, the target is 85–95% RH and 75–80°F air temperature inside the dome. The dome creates this environment passively — mist the dome walls (not the leaves) if condensation has completely cleared. Condensation on dome walls is your visual humidity indicator. Keep PPFD at 75–150 µmol/m²/s — T5, CFL, or a dimmed LED at 24–36" above the canopy. Do not apply full veg-level lighting to rootless cuttings.
Follow the venting schedule exactly on the calendar dates shown
The schedule progresses: 15 min venting twice daily → 30 min → 1 hour → dome off during lights-on only → dome fully removed. Each phase lasts 2 days. The calendar dates in the schedule are based on your actual stick date and first-roots offset — they account for your specific timeline. If a clone wilts during a venting session, close the dome and give it another full day before trying again. Wilting during venting means roots aren't established enough yet — it's a diagnostic, not a failure.
Maintain 60–70% RH for 48 hours after dome removal
The transition to open air isn't complete when the dome comes off. Clones that have been in 85–95% RH need a couple of days at 60–70% RH before they're fully acclimated to standard veg conditions. If your grow room is below 55% RH, run a humidifier near the clone tray for the first 48 hours post-dome. After that, they're ready to go into veg conditions. Use the VPD Calculator to confirm clone/seedling VPD (0.4–0.8 kPa) in their new environment.
Why the 8-day venting protocol, not just "open when rooted"
A clone that has been rooting in 90% RH for 8–10 days has stomata that have barely regulated water loss — they've been in a near-saturated environment. Suddenly dropping to 55–60% RH causes the leaf surface to lose water faster than the newly-formed root system can replace it, even though the roots technically exist. The 8-day protocol gives stomata time to recalibrate their regulation behavior progressively. Each stage of the protocol reduces RH by roughly 5–8 percentage points — small enough that the stomata adjust, large enough that the transition completes in reasonable time.
Stomatal regulation, VPD during propagation, and why light needs to be low
Clone propagation is a race between two processes: the cutting's water loss through transpiration, and the root development that will eventually allow water uptake to replace that loss. The dome environment is designed to reduce the transpiration side of that equation to near zero until roots can support the other side. See the Propagation Guide for the full cloning reference.
0.3–0.6
Clone dome VPD (kPa)
Much lower than veg VPD (0.8–1.2 kPa). Low VPD minimizes transpiration so the rootless cutting doesn't desiccate. Stomata barely open in high-humidity conditions.
75–150
Target PPFD (µmol/m²/s)
One-quarter to one-sixth of flowering PPFD. Clones need light for minimal photosynthesis but high PPFD drives transpiration and stresses a cutting that can't replace lost water.
8 days
Progressive acclimation period
Time for stomata to adjust from minimally-active (dome) to actively-regulating (open air). 8 days of progressive exposure prevents the wilting that kills rooted clones when dome is removed too fast.
What the dome is actually doing
Cannabis leaves lose water through stomata — microscopic pores on the leaf surface. Transpiration rate is driven by the vapor pressure gradient between the leaf interior (nearly 100% RH) and the surrounding air. In a high-humidity dome (85–95% RH), this gradient is very small — the air is almost as humid as the leaf interior, so very little water escapes. This is how a rootless cutting survives: it's not taking up water (no roots), but it's barely losing water either.
As roots develop, the cutting gains the ability to take up water through its stem base. The venting protocol transfers the clone from "survival by low transpiration" to "survival by normal water uptake" gradually, giving roots time to establish enough capacity to support increasing transpiration demand.
Why PPFD must stay low during propagation
Light drives photosynthesis — but it also drives stomatal opening and transpiration. High PPFD causes stomata to open wider to exchange CO₂ and O₂ for photosynthesis, which simultaneously increases water loss. A cutting under 600+ µmol/m²/s light is losing water at active veg rates while having no roots to supply replacement water. Low PPFD (75–150 µmol/m²/s) provides enough light for minimal photosynthesis while keeping stomatal opening — and thus transpiration — at a level the cutting can survive.
| Method | Dome RH target | VPD target | Key maintenance |
|---|---|---|---|
| Humidity dome | 85–95% | 0.3–0.6 kPa | Mist dome walls if condensation clears. Keep vents closed until first roots. |
| Aeroponic cloner | 65–75% (room) | 0.6–0.9 kPa | Reservoir at 68–72°F. Change water every 5–7 days. Clean nozzles monthly. |
| Open-air | 70–80% (ambient) | 0.5–0.8 kPa | Mist leaves lightly every few hours. Only viable in naturally humid environments. |
Common dome venting questions
My clone wilted during venting — what do I do?
Close the dome immediately and give it a full day of recovery. Wilting during venting means roots aren't established enough to support transpiration at lower RH. It's not failure — it's a diagnostic telling you to slow down. After the dome is back on and the clone recovers turgor, try the same venting duration again the next day. If it wilts again at the same duration, stay in that phase for another day before advancing. The clone will tell you when it's ready to progress. Clones that wilt once and recover usually transplant successfully; clones that wilt and don't recover (leaves stay limp after dome is replaced) may not have viable roots.
How do I know when the dome is actually ready to come off?
Two signals together: the clone holds structure (no wilting) for a full lights-on period without the dome, and the tug test shows firm resistance. A clone that passes both tests is ready for full dome removal. If it holds structure but has soft tug resistance, it has enough roots for the dome to come off but may benefit from another day before transplanting. If it wilts without the dome but the tug test shows resistance, the root system is established but the stomata haven't acclimated yet — continue the Phase 4 protocol (dome off during lights-on, dome on at lights-off) for another day.
Can I skip phases if my clones look vigorous?
You can compress the schedule if clones are genuinely robust — strong tug resistance, thick new leaf growth, very vigorous root tips. In that case, you can combine Phase 1 and 2 into a single day (30 minutes from the start rather than 15 minutes), and similarly compress Phase 3 and 4. The 8-day schedule is conservative by design — designed for clones that have average root mass at the standard first-roots date. Aeroponic clones that root in 5 days often have vigorous enough roots that the schedule can be compressed to 5–6 days. Watch the clone's response, not the calendar.
Do I need to vent if I have a vented dome lid?
Sort of — but you still need to follow a gradual protocol. Vented dome lids have adjustable vents that you can crack slightly during the early phases (Phase 1 and 2) rather than physically lifting the dome. This is actually easier and more consistent than lifting the dome, since you can dial in a consistent crack width. The protocol timing is the same: crack slightly for Phase 1, open the vents halfway for Phase 2, open fully for Phase 3, then remove dome for Phase 4 and 5. Vented lids make the protocol easier to follow precisely.
What RH should my grow room be for newly transplanted clones?
60–70% RH for the first 3–5 days post-transplant, which corresponds to the clone/seedling VPD target of 0.4–0.8 kPa. After that, you can transition to standard vegetative VPD (0.8–1.2 kPa). If your grow room runs at 50–55% RH during veg, run a small humidifier near the transplanted clones for the first few days — the jump from dome RH to a dry veg room can cause transplant shock even in well-rooted clones. Use the VPD Calculator with the corrected temperature and RH to confirm you're in the clone/seedling target range.
Propagation environment essentials
The dome environment is simple to maintain with the right equipment. Heat mat, vented dome, and a $10 hygrometer inside the dome cover the essentials.
Humidity domes — vented lids
Vented 7" humidity dome ($10–15), standard 3" dome ($6–10), dome with adjustable vents ($12–18). Vented lids make the progressive venting protocol much easier — you can dial in exact vent width rather than timing dome lifts. Tall domes (7") accommodate clones with more lateral growth. Standard 10×20 trays fit standard cell inserts and heat mats.
Heat mats & thermostats
10×20 heat mat ($15–25), mat with thermostat ($35–60). Maintains root zone at 72–78°F independently of ambient temperature. The thermostat version is worth it — without one, the mat can overshoot on warm days and push root zone above 82°F (pythium risk). Probe under the tray reads actual root zone temperature.
Hygrometers for inside the dome
Compact digital hygrometers ($8–15). Put one inside the dome to confirm actual dome RH — not the ambient RH of the room. Dome interior can vary significantly from room conditions depending on how well the dome seals. Knowing the actual dome RH lets you identify whether condensation loss means humidity is dropping below the 85% target.
Propagation media
Rapid Rooter plugs, Jiffy pellets, rockwool cubes, coco plugs. Media choice directly affects rooting speed and the dome venting timeline — aeroponic cloners root fastest (5–7 days), soil slowest (10–14 days). Pre-moisten all media to field capacity before use. Oversaturated media reduces oxygen at the root zone and slows callus formation.
Aeroponic cloners
Turbo Klone, Clone King, Ez-Clone systems. Eliminates the dome entirely — no humidity management needed beyond maintaining room RH at 65–75%. Roots 30–50% faster than plug methods. The tradeoff: requires reservoir temperature management (68–72°F) and regular nozzle cleaning to prevent pythium. Worth it for growers running 3+ clone batches per year.
Rooting gel & hormones
Clonex, Olivia's Clone Solution, GH RapidStart. Rooting gel at 3,000–8,000 ppm IBA accelerates callus formation and root initiation by 2–4 days. Pour a small amount into a shot glass and dip each cutting — never double-dip the container. Rooting hormone is not strictly required but improves success rate and reduces time to first roots, which directly shortens the dome phase.