Begin by washing your hands and putting on gloves. Place the culture vessels on a clean or sterilized surface, then gently remove the plantlets from their containers.

Carefully rinse the roots with distilled water to remove all traces of gel or sucrose-based media. Any remaining residue can promote fungal or bacterial growth once the plant is exposed to non-sterile conditions.

At this stage, remove any yellowing, brown, or damaged leaves using tweezers, Castroviejo scissors, or clean hands. Be gentle and aim to preserve as much healthy tissue as possible.

Some growers choose to apply a preventative fungicide treatment. This can be done by soaking plantlets for 5–10 minutes in a solution of distilled water mixed with Physan 20 or Captan, following the manufacturer’s dosage instructions (typically just a few drops per gallon). Afterward, rinse the plants by soaking them in plain distilled water for an additional 10 minutes. This step can help reduce the risk of fungal infections during early acclimatization.

Plantlets should not be transferred directly into regular soil. Instead, they should be placed into a sterile, well-aerated medium that retains moisture without becoming waterlogged.

Common acclimatization media include:

• Sphagnum moss

• Perlite

• Vermiculite

• Peat

• Fluval Stratum

• Blends of the above

In our experience, the most reliable options have been:

• Sphagnum moss alone

• Sphagnum moss mixed with perlite

• Fluval Stratum

These combinations work particularly well for aroids and many tropical species. Carnivorous plants, on the other hand, often perform best in pure sphagnum moss. As with conventional plant propagation, the ideal medium depends on the genus and species you are working with.

Pro Tip:
If you are acclimating a plant genus for the first time and have multiple plantlets available, consider experimenting. Plant individual specimens in different media to determine which performs best under your conditions.

If your plantlets already have a well-established root system, a more cost-effective option such as sphagnum moss or a sphagnum–perlite mix may be sufficient.

Once your medium is prepared in a small pot, create a hole with your finger, gently place the roots inside, and lightly cover them. Ensure that the shoots remain above the surface and are not buried.

Because in vitro plants lack many protective structures found in naturally grown plants, sudden exposure to greenhouse or household conditions can be fatal.

To prevent this, place the potted plantlets into a transparent, enclosed container—essentially a mini greenhouse. The container should be large enough that leaves do not touch the walls, which can cause condensation-related damage.

At this stage, the container should remain fully sealed. The plants are accustomed to nearly 100% humidity, and the goal initially is to change only the growing medium—not the environment.

Maintain this closed environment for approximately 2–4 weeks, or until the plant produces new leaves and additional root growth. Once the plant shows signs of active growth, begin the gradual acclimation process.

This can be done by:

• Opening the container lid for one minute per day and slowly increasing the duration over time, or

• Creating small ventilation holes and gradually increasing airflow

As ventilation increases, humidity will naturally decrease, allowing the plant to adapt.

Pro Tip:
If available, a greenhouse is an ideal environment for this stage, as it offers a more controlled transition than a dry indoor setting.

Environmental Conditions to Maintain

During early acclimatization:

• Light: Low-intensity or shaded light

• Humidity: 80–90%

• Temperature: 22–25°C (68–77°F)

Gradually increase light intensity and decrease humidity over several weeks.

Avoid overwatering, as excess moisture can quickly lead to root rot. Keep the medium lightly moist, using a mist spray if necessary. After a few weeks, gentle airflow from a fan can help strengthen stems and improve overall plant structure.

Cold Climate Tip:
If temperatures are low, a seedling heat mat may be used. However, avoid combining bottom heat with high-intensity lighting, as excessive heat from both directions can severely stress or kill young plantlets.

After approximately 4–8 weeks, once plants are fully acclimated and showing stable growth, they can be transferred to larger containers.

At this stage, plants may be moved into:

• Regular potting soil

• Semi-hydroponic systems

• A larger container with the same acclimation medium

Continue monitoring plants closely for signs of stress, including wilting, discoloration, or leaf necrosis.

Plants that are not properly hardened often exhibit symptoms such as leaf tip burn, margin necrosis, severe wilting, or complete leaf loss.

Materials You May Need for Plant Acclimatization

At Plant Cell Technology, we aim to make tissue culture more accessible and successful. Below is a list of commonly used materials for acclimatization:

• Round snap-lock containers

• Sterile Petri dish packs

• Physan 20 (algaecide, fungicide, bactericide)

• Coarse horticultural-grade perlite

• Dried orchid sphagnum moss

• Fluval Plant & Shrimp Stratum

• Full-spectrum LED grow lights

• Surgical-grade blades

• Castroviejo scissors (5.5”)

• 99% isopropyl alcohol