Why weaning takes four weeks
A plantlet grown in a tissue-culture cup has lived its whole life at near 100% humidity, on sugar-rich agar, under gentle light. It has barely needed to protect itself. Its leaves carry only a thin waxy cuticle, its stomata — the pores that open and close to control water loss — have never had to close, and its roots were built for gel, not air. Take it out of the cup and put it on a windowsill at 50% humidity and it can lose water faster than it takes it up within an hour. That is why most failed deflasks wilt on day one or two and never recover.
Weaning, or acclimatisation, is the process of lowering humidity gradually so the plant can build a proper cuticle, train its stomata and grow functional roots in a real substrate. We use a four-week schedule on our benches in York. It is not the fastest possible, but it is the one that loses the fewest plantlets, particularly with expensive variegated aroids where every plant counts. This chart prints that schedule with real dates, so you know on any given morning which phase you are in.
Day 0: the deflask itself
Work on a clean surface with clean hands. Ease the plantlets out of the cup, then rinse every trace of agar from the roots in tepid water. Agar is a sugar gel, and any left on the roots becomes food for moulds in the warm, humid dome that follows; this is the most common cause of losses in the first week. A short soak in a root-conditioning solution such as X-Vitro helps roots that have only known gel. Separate clumps gently if they come apart easily; if not, plant the clump as one and divide later.
Choosing the rooting media
Plantlets need air and moisture at the roots in equal measure. Grade-A long-fibre sphagnum moss, squeezed until damp but never wrung dry, is the most forgiving choice and the one we use for most aroids. A 50/50 mix of fine perlite and screened fine pine bark drains faster and suits growers who tend to overwater. A fine pumice matrix suits anyone planning to move the plants into semi-hydro later. Whatever you choose, it must be sterile or freshly opened; garden compost and old potting mix bring fungus gnats and moulds the plantlet cannot fight. More on media is in our step-by-step acclimatisation guide.
Phase 1 (days 1–7): sealed
Keep the dome or box closed at 95–100% humidity, under soft LED light of around 60–100 µmol/m²/s for 12–14 hours a day, with bottom heat near 22–25°C. Do not vent. The plant is forming its first real cuticle. Check daily through the lid for grey fluffy mould at the base of the stems, which usually means agar was left behind; remove affected material at once.
Phase 2 (days 8–14): first breaths
Crack the vent about a quarter, or lift the lid for 30 minutes a day, aiming for 85–90% humidity. This is when stomata start to work. Watch the leaves for an hour after venting: if they droop, close up and try again the next day. Look through the clear cup wall for white root tips; new roots are the best sign the plant has accepted the media.
Phase 3 (days 15–21): half open
Open the vents 50–75% and let humidity settle at 70–80%. Give the first feed at quarter strength, a balanced fertiliser at around EC 0.4–0.6 mS/cm. Check turgor an hour after opening; firm, upright leaves mean the plant is coping.
Phase 4 (days 22–28): dome off
Remove the cover and let the plants harden at 55–65% humidity, either in the room or a cabinet. If your room sits well below that in winter, keep the plants in a cabinet or on a humidity tray rather than rushing them. At the end of the week a rooted plantlet is ready to step up into a 6cm clear slotted pot with a fine starter mix, then into a genus blend such as our Monstera & Philodendron mix once roots fill the pot.
Using the check log
Write the humidity, temperature, leaf turgor, any mould and whether root tips are visible at each check. Patterns matter more than single readings: a plantlet that droops after every vent needs a slower step, while one with roots against the wall by day 10 can move a little faster. If you buy cups from us, our tissue-culture range includes the dome, moss and starter pots this chart assumes.