How To Raise Tissue Culture Plants

If you’re a houseplant enthusiast, you’ve probably heard of tissue culture propagation. If you haven’t, you’re in luck, because we’re going to get into the details of it today. For many people, even plant collectors who are familiar with stem cutting or wetstick propagation, tissue culture may sound intimidating.  

But the good news is this: tissue culture means that many rare plants that were once inaccessible due to scarcity and high costs are now becoming available on the market. And with a little extra care, you can raise them in your home. 

What is Tissue Culture? 

This is a method of propagation—plant reproduction—that requires sterile, laboratory conditions. Tiny pieces of tissue are taken from the parent plant and grown in a gel-like solution of the nutrients a plant requires, making an exact clone of the parent called a plantlet. These plantlets are nurtured until they are strong enough to venture out into the world—but they still require much different care than a conventional plant you pick up from the nursery. 

Bringing a TC Plantlet Home 

As tissue culture propagation grows in popularity, these plantlets are becoming more readily available on the market, especially online. If you purchase a plant, it will arrive in a solution of nutrients and sugar called agar—and will need to undergo the slow, patient process of acclimation. 

The first step is to remove the plantlet from the agar solution and clean it, being careful to remove all of the agar from the leaves and roots. Because the plant has only ever existed in a sterile environment, this is an essential step in order to ensure the plant will grow healthy and strong. 

The plantlet will be very small and fragile. Supporting the base and the roots, wash carefully with lukewarm, distilled water. Imagine a tomato seedling that has only just emerged from soil: it’s unable to tolerate very much force or pressure. The last thing you want to do is damage the plantlet when it’s only just arrived! 

Any amount of agar residue left over can be harmful to the plant and may cause bacterial growth, trap excess moisture which can lead to root rot, and send the plant into shock before it has a chance to get established. 

 Once you’re through, inspect the plantlet and remove any damaged or discoloured tissue. 

Hardening Off 

The next step in the process is to connect the gap between the plantlet’s former sterile conditions, and the environment in which it will spend the rest of its days. This is a process called hardening off. 

Much like taking seedlings outdoors so they can grow accustomed to wind and sun, your tissue culture plant needs to similarly transition. 

Because the plantlet has so far spent its existence in a sterile environment with almost complete humidity, it can struggle with moisture retention and become vulnerable to disease and pests. 

It’s too soon at this point to plant your TC plantlet into potting soil, which is too dense and retains more moisture than the plant can handle. A good medium for the plantlet to harden off is a mixture of perlite and sphagnum moss, or perlite and coco coir. This offers good drainage while allowing the plant to grow accustomed to a different, still largely sterile environment. 

Using small pots with drainage holes, gently loosen the roots and place the plantlet into the substrate, being sure not to bury it too deeply. Press around the substrate so it’s secure but not compacted. 

During this time, the plantlet still requires a high level of humidity. Place the pots under a plastic dome, into a container, or a clean, resealable plastic bag. Anything you have that will trap moisture without airflow, but that is transparent to allow light in. 

This is the new climate for your plantlet while it adjusts to your home. 

Your plantlets require bright, indirect light; direct sunlight can burn the sensitive tissue, especially in an enclosed environment. Not enough light can weaken the plant, disallowing it from taking hold and beginning to grow. An ideal solution is placing the plantlet’s new enclosure under grow lights. 

The Adjustment Period 

It will take a number of weeks before your plant is fully acclimated to your home and ready to join your collection. Be careful not to rush this process, or all of your efforts may come to nothing if the plantlet doesn’t make it. 

Keep in mind, by this point the baby plant has been (likely) shipped from one location to another, handled for cleaning, and relocated into a completely new substrate. All of this is a massive shift for an already vulnerable being, and the plantlet will be in shock. These first weeks are the time for recovery. 

Maintain a high level of humidity, keeping the enclosure sealed without any significant airflow. Moisture needs to remain consistent in the substrate; not drying out, but not overly saturated to the point where the roots are drowning. 

During this time, your plantlet will establish itself in the substrate, and begin developing new roots. 

After the first week or so, once the plant has begun to stabilize, remove the lid to allow a small amount of airflow for up to thirty minutes per day. Carefully observe the plant, and at any signs of drooping or curling, allow more time inside the dome. 

This is the beginning of the adjustment to lower humidity. 

Once the plantlet seems to be adjusted, increase the amount of open airflow, up to several hours per day. Rather than keeping the lid fully sealed otherwise, keep it slightly off so the plant will experience mild airflow even when the lid is in place. 

Ensure you monitor the plant throughout for any signs of weakness or struggle, including yellowing of leaves. If the plant looks strong and healthy, or even begins to show signs of new growth, that’s a sign it’s doing well with the adjustment process. 

The final stage of acclimation is to remove the enclosure altogether. This is the biggest test for the tissue culture plantlet to ensure it will be able to survive the atmosphere in your home. If the plant shows signs of struggle at this point, take a step back. 

Even once the plantlet emerges into the climate of your house, do what you can to provide it with stable, consistent conditions. Controlled humidity, a bright, indirect light source, and consistent watering in a well-draining substrate. At this point, the plantlet has graduated to the rest of your collection, but just like any other not-yet-established plant, it will require just a little extra care. 

Settling In 

The key to this entire process is patience. Just like it takes time for a plant from the nursery to adjust and grow, it will take time for a tissue culture plantlet to grow accustomed to a new environment. Chances are, if you’ve gone to the trouble of ordering a tissue culture specimen in the first place, it’s a rare or desirable plant. So you might as well take care of it from the first day it arrives in your home if you want it to live a long and healthy life in your care. 

Here are a few additional pointers. 

●     Consistency is important. Maintain the plantlet’s conditions as well as you can, especially while it’s adjusting. Sudden changes in temperature, humidity, or substrate can cause any plant to go into shock. A struggling plant is one that is vulnerable to pests and disease. And those with optimal conditions tend to produce well. 

●     Don’t fertilize the plant until it’s well established and begins showing signs of outward growth ie. new leaves. Fertilizers can harm the roots, especially when too strong or too frequent. 

●     When it’s time to repot into soil, ensure you have proper drainage. A good mix of potting soil with other amendments like perlite, orchid bark, coco coir, etc. can provide a good environment for a plant to grow. A soil that is too dense will retain too much moisture and allow for potential root rot. 

●     Even if you think your plantlet is doing well, don’t pull the roots to check. Patience in this case is relying on the plant to do what it needs to do below the surface, often well before it shows any outward signs of growth. A plant will prioritize healthy roots before it can do anything else, and a tissue culture plantlet won’t have the necessary root system for some time. 

●     One of the biggest threats to young TC plantlets is cleanliness, or the lack thereof. Although they are no longer in a sterile environment, it’s important to ensure the plant’s conditions are clean. Bacterial and fungal pathogens can kill a young plant when it has no means to protect itself. Wash your hands or wear gloves before handling them, and consider immersing the plant in a mild solution of fungicide and distilled water. 

Lastly, this all can come across as intimidating. If you have multiple tissue cultures of the same plant, take the time to learn and experiment to see which methods work best for you. As with all aspects of gardening and plant care, there is no such thing as perfection, and mistakes happen. Take an opportunity to try something new; you’ll always learn something along the way. 

Until next time!