How to Deflask Carnivorous Tissue Culture

Deflasking is the moment a tissue culture plantlet leaves its sterile vessel and starts living in the real world. It is the step people are most nervous about and, for carnivorous plants, the step where the standard advice will actively kill your plants.

The process itself is the same one we use for tropical aroids. Three things change, and all three matter more than anything else on this page.

The three changes, up front

1. Every drop of water is mineral free. Distilled, reverse osmosis or rain. That includes the rinse water and the peroxide soak, not just what you water with afterwards.
2. The media has no nutrients in it. Pure long fibre sphagnum, or a peat and perlite mix. Never an aroid mix, never potting compost, never anything with fertiliser.
3. More light once it is hardened off. Most carnivorous plants want considerably more light than a tropical plantlet, with Nepenthes the exception.

Get those three right and the rest is ordinary acclimation.

What you will need

• Distilled or RO water, more than you think.
• Long fibre sphagnum, or peat and perlite. Unfertilised, always.
• A humidity dome, a propagator lid, or a clear tub.
• Hydrogen peroxide, a few drops per cup of water.
• Small pots or a community tray.
• Scissors and a bit of patience.

Step by step

1. Let it rest

Leave the sealed vessel somewhere at room temperature in normal room light for a day or two. The plantlets have been in transit and they stabilise better if they adjust to your ambient conditions before you open anything. There is no rush.

2. Open and separate

Cut the container open rather than fighting the lid. Lift the clump out gently. Tissue cultured plantlets usually come out as a mass with roots tangled together in agar, and they separate more easily than they look like they will once the agar is softened.

3. Rinse every trace of agar off

This is the step that decides whether you get mould. Agar is a sugar rich jelly, and any left on the plant becomes food for fungus the moment it is exposed to open air. Rinse under running distilled or RO water until the roots are genuinely clean, not just mostly clean.

Use mineral free water here, not tap. People often use tap for the rinse on the logic that it gets washed off anyway. It does not entirely, and this is the first of many small mineral doses that accumulate.

4. Trim

Remove anything yellow, mushy or obviously failing. It does not need to be neat. Leave healthy roots alone and do not strip every leaf: the plantlet needs something to photosynthesise with while it establishes.

5. Sterilise

Soak the cleaned plantlets for a few minutes in mineral free water with a few drops of hydrogen peroxide per cup. This knocks back fungal spores picked up during handling and reduces early rot.

6. Pot into carnivorous media

Pure long fibre sphagnum works well and is forgiving. A peat and perlite mix works too. Nepenthes prefer something airier, so lean on sphagnum with added perlite or bark for those.

What you must not use: any aroid mix, any potting compost, anything containing fertiliser, and anything containing lime. Carnivorous plants get their nutrition from insects, and the fertiliser in ordinary media burns their roots. This is the single most common way a deflasked carnivorous plant dies in week one.

7. Harden off under a dome

Start at close to 100% humidity under a dome or lid. Over ten to fourteen days, introduce progressively more room air: crack the lid a little wider each day, or add and enlarge ventilation holes. The plantlets have been living in saturated air their whole lives and have no cuticle to speak of, so a sudden move to open air desiccates them.

Keep the media damp throughout with mineral free water. Not sodden, and never standing in it during this phase.

8. Bring the light up

Once out of the dome, most carnivorous plants want strong light, and considerably more than a tropical plantlet would. Flytraps, Sarracenia and most Drosera want as much direct sun as you can give them. Increase it gradually over a couple of weeks rather than moving straight to a south window, since a plant fresh out of a dome will burn.

Nepenthes are the exception and want bright filtered light rather than direct sun. Applying flytrap light levels to a Nepenthes will scorch it.

Species differences that actually matter

• Venus flytrap (Dionaea): temperate. Will want a winter dormancy once established. See is my flytrap dead or dormant?
• Sarracenia: temperate, same dormancy requirement, and greedy for direct sun.
• Nepenthes: tropical. No dormancy, filtered light, airier media. The most forgiving of the group to deflask.
• Drosera: mixed. Temperate species want dormancy, subtropical species do not. Worth knowing which you have.

A note on timing

Growers commonly report that temperate species deflasked in autumn will try to enter dormancy before they have properly established, and struggle as a result. If that matches your experience, spring and early summer are the safer window for flytraps, Sarracenia and temperate sundews. Nepenthes, having no dormancy, can be deflasked at any time of year.

What usually goes wrong

• Mould within days: agar was not fully rinsed off.
• Steady decline over weeks: tap water, or fertilised media. Both are slow and both are fatal.
• Collapse right after the dome comes off: hardened off too fast. Go back a step and take longer.
• Scorching: too much direct light too soon, or full sun on a Nepenthes.
• Rot at the crown: media too wet during hardening off.

Related reading

The general process for tropical plants is in our tissue culture acclimation guide. The water question is covered properly in what water should you use. And if you would rather skip deflasking entirely, plugs are the hardened off alternative.

Browse carnivorous plugs and tissue culture when you are ready.