In Vitro or potted plants?Decision support when buying aquatic plants
Many aquatic plant species are offered in various forms in commerce, and we are often faced with the question which variant to buy. In recent years, plants cultured in the In Vitro form have become more and more popular. The aquatic plants are cultivated in laboratory conditions using the tissue culture method and are sold directly in their respective culture cup.
In all other conventional forms of delivery the plants are not sterile. A classic variant is the purchase of aquarium plants as pots. Most potted plants are cultivated in their emerged form in their plant nurseries, meaning they are kept above water. Usually rockwool is used as a substrate.
Potted plants that have been cultivated under water (submerged) are also available, especially those species that can grow only submerged. Submerged plants, especially stem plants, are also available in bunches, floating plants mostly as a portion in plastic cups.
No matter if In Vitro- or potted plants - every form of delivery has its up- and downsides. Here we’ll give you a couple of tips for the purchase of aquarium plants in their appropriate form.
In Vitro aquatic plants offer several benefits. They are free of pesticides and unwanted foreign organisms such as parasites, pathogens, snails, planarians, insect larvae, algae and annoying "weeds" such as duckweed. The pesky removal of rock wool is omitted completely. And with one portion you get quite the large number of small individual plants. But there are also a lot of untrue rumors and myths about in vitro plants. We would like to clarify some things here first:
"The plants are already cultivated in their In Vitro cups while being submerged."
This is, of course, wrong. There is only a nutrient gel at the bottom of the cups, above that only air. The aquatic plants clearly grow in their emerged form, though the In Vitro cultivation is rather peculiar. Due to the confined space, the method of procreation (cultivation from small bits of tissue) and the special composition of the growing medium, the In Vitro plants grow in a small form. The plants develop their full size and species- and variety-typical look.
Easily discernible: The special, small growth habit of a Rotala species under In Vitro conditions.
An exception to this are some plant varieties that need to be cultivated submerged in liquid growing media such as Potamogeton gayi and Fontinalis antipyretica.These plants are actually already submerged.
Potamogeton gayi in liquid growing medium.
"In Vitro plants have a tremendous shelf-life."
This, too, is not quite correct. First and foremost, the growth habit and durability of a plant differs from species to species. Some plant species such as Cryptocorynes or Eleocharis definitely are pretty durable, for several weeks. But this is especially not applicable to fast-growing species such as stem plants. With a longer shelf life, these can sometimes even grow so rapidly that due to the plant mass, the lid of the cup will pop off. It may also happen in more lushly grown In Vitro cups, that the lower leaves get too little light and die. This might not look too visually appealing, but is definitely no big deal especially with stem plants, since the healthy shoot tips will keep growing well in the aquarium. Also, the storage conditions need to be appropriate for In Vitro plants. Moderate lighting and an air-conditioned, cool cup storage.
"The colour of the growing medium is a telltale sign that the plants have been sitting in the shelf too long."
This, too, is incorrect. First of all, some manufacturers use differently-coloured growing media, and on the other do some plants (e.G. Marsilea species and Heteranthera zosterifolia) emit substances that change the colour of the growing medium.
"The consistency of the growing medium is a telltale sign that the plants have been sitting in the shelf for too long."
This is not correct. Both, colour and consistency may vary from supplier to supplier. For example, the supplier Tropica has recently started using a growing medium that is no longer a firm gel, but a liquid (as mentioned above). This has no negative impact on the quality of the plants. Quite the contrary: You don’t have to remove any gel residue from the plants’ roots, you just dump the growing liquid and are ready to go. The plants can be used much faster this way. Furthermore, the liquid medium also allows the in vitro culturing of plant species that can grow only under water - like the already mentioned Potamogeton gayi.
"In Vitro plants always grow better and faster than potted plants."
Nope, quite the contrary, actually. Potted plants have it easy during the acclimatization- and adaptation phase as they are bigger and more robust than plants from In Vitro cultures. You should also understand, that the initially germ-free In Vitro plants are introduced directly into the germ-heavy aquarium millieu and need to develop an immune system first.
"Pronounced roots are a telltale sign of the cup’s shelf-life."
This is incorrect and yet again dependant on species. Some plants might not take root at all in an In Vitro cup, where others grow like there’s no tomorrow. This has nothing to do with the shelf-time of the cup, though.
"In Vitro are specifically suited for Wabi-Kusa or a Dry Start."
No, because from experience, emerged potted plants have a bigger advantage. They are more robust and do not need to adapt as severely to a new planting situation as In Vitro plants. For a Wabi-Kusa or Dry Start, emerged, potted plants are to be preferred.
Potted aquarium plants are, as initially mentioned, usually plants cultivated in their emerged form. They are rooted in a special substrate, live in a plastic mesh-pot and are fed with a nutrient solution. The substrate is as already mentioned usually rockwool but may also be made of coconut fibres. It may contain residues of fertilizers, possibly also algae or foreign plants such as duckweed. Therefore, you should remove the substrate as completely as possible before use in the aquarium (instructions for that can be found here).
But especially with ground cover, the rockwool can be strategically used to better anchor the plants in the soil (this is described in this article.
In rare cases, emerged potted plants might be accompanied by little animals that have been living in the plants during their time in the plant nursery. These may be little slugs and insects like aphids, whiteflies and thrips. This is usually not an issue for aquaristic purposes, since those critters are confident land-dwellers and can not survive under water or rather get eaten by the ornamental fish.
Emerged potted plants usually have no aquatic fauna such as water snails and planaria living in them, but the pots are stored wet during cultivation and keeping, so such “copilots” in the pots and substrate can not be ruled out completely. Especially not with submerged potted plants such as Blyxa japonica or Vallisneria.
Emerged potted plants are characterized by their robustness. A further important criterium is the already established plant height, because potted plants like ferns, Anubia, stem plants and rosette plants such as Cryptocorynes und Echinodori are generally much larger in size and length than in-vitro plants. If such plants are planted in the background or middle ground of an aquarium behind higher hardscape constructions, a height of over 10 cm is already a clear advantage. The plants can reach the light much better and aren’t shaded by stones or driftwood and thus inhibited in their growth. Also they are so voluminous from the very beginning, that they can provide greenery to an aquarium from day one. In contrast, In Vitro plants are only a few centimeters high and small in circumference.
- Anyone who attaches great importance to a sterile, clean environment and would like to have no algae spores, snails or parasites in the initial planting of his aquarium, is clearly best advised in getting the In Vitro version. However, these plants usually need a little longer for their changeover.
- Especiall ground cover like Eleocharis or is pretty rich as an In Vitro portion and you get quite a lot of plants for your money.
- For the purchase of stem plants for backgrounds as well as epiphytes- and rosette plants for the back- or middle ground, we definitely advise getting the potted variant. Potted plants are much more robust, have a faster changeover and already have an advantageous growth height. However, some rare stem plants are only available as In Vitro product. To prevent the abovementioned problem of shading, it is often worth growing those plants close to the water surface in a Plant Pod.
- For the design of a Wabi-Kusa or the application of the Dry Start method, emerged potted products have a clear advantage especially with stem plants.
- Who doesn’t know the problem of having tiny bits of foreign plants, like other moss species, in a freshly-purchased moss? These intruders, like the rampant Riccia fluitans, can be quite unwanted. To be on the safe side, you should buy mosses as an In Vitro product.