The colocasias (genus colocasia) are very common plants from tropical and subtropical areas of Asia, from the family Araceae. The genus comprises about 25 species (only 11 accepted today) that can be grown both indoors and outdoors, and among them are some very cold resistant. All of them can be kept outdoors in summer, but if we live in an area with severe frosts, we will have to keep most of them at home when winter arrives.
They are plants that cannot be missing in a tropical garden in a frosty climate, and there are a wide range of colors. Read on to discover general collocasia care and cold hardiness and the appearance of its most interesting species and cultivars.
All of them are rhizomatous herbaceous plants, with heart-shaped leaves very similar to those of the alocasias, which also gives them the common name of elephant ears. They are usually small plants, rarely exceeding one meter in height. Usually lack aerial stem, although its rhizome, in many species reduced to a corm, sometimes appears above the ground. What usually appears to be a stem is actually the pseudostem formed by the leaf sheaths. Regarding coloration, wild species are usually dark or light green, with very marked nerves. But there are all kinds of cultivars of different colors that we will see later. The leaves usually have a more or less vertical petiole and a blade with the tip pointing downwards.
Flowering is typical of araceae, having an inflorescence formed by a spadix (fleshy spike of seated flowers, the female at the base and the rest male) and a spathe (colored bract typical of this family, which appears to be a large petal). The colocasias usually have a white spadix and a yellow spathe, open on the male part and with the green base forming a sheath that protects the female flowers. To reproduce they use the seeds, stolons and bulblets that appear attached to the rhizome.
They can be grown both indoors and outdoors, but it is always much better to have them outside and to be able to be in the ground, at least during the summer.
Substratum: They are not delicate with the type of substrate, but they prefer them fertile and always humid, with good drainage. Some species can grow in flooded or directly flooded soils, but unless you know for sure, it is better to give them good drainage.
Irrigation: During the growing season (between spring and autumn in cold areas) they require a lot of water, preferring to have the substrates always humid. In the dormant season, you only have to water enough so that the substrate is not completely dry. Not all species go into rest, so we have to know our plants and know what they ask of us.
Subscriber: highly recommended to add compost during the growing season. The doses and time between subscribers will be those indicated by each product. If our plants turn yellow it is an indicator that they are lacking some nutrient, normally it will be nitrogen or iron, so with a normal fertilizer and a little iron chelate it is usually solved.
Exhibition: Depending on our climate they will tolerate full sun or not, but it is always advisable to put them in semi-shade, especially in hot and dry areas. Indoors they will have to be attached to a window where the sun hits them to grow fairly well.
Temperatures: They depend entirely on the species. Almost none will have problems with the heat if it is in semi-shade, but the resistance to cold ranges from almost -15ºC of 'Pink china' to directly not supporting the cold maintained. Those that come to rest usually do so with the first frosts or a little earlier, at which point if we live in a climate that is too cold for them, we will be able to tear off the rhizomes and store them as if they were bulbs. The most tropical ones it is advisable to keep them in a heated greenhouse or indoors to spend the winter growing.
Plagues and diseases: In general, they are very tough plants, but they can be attacked by snails and slugs, rot if they remain stagnant in the dormant season and chlorosis caused by nutritional deficiencies.
Some interesting collocasias
We have selected some colocasias with striking characteristics, be it their coloration or their resistance. Before knowing them, it is important to know what they are: when the name after the gender is enclosed in single quotes (such as colocasia 'Pink china'), it is a non-fertile hybrid (or hybrid cultivar), that is, a specimen selected from among those that have germinated from seeds from a female flower pollinated with pollen from a different species of Colocasia. If the name in quotes follows the species (like colocasia esculeta 'Black coral') is a cultivar, that is, a selected specimen of that species. We are going to talk about their appearance and the characteristics that make them unique.
colocasia esculenta (taro or taro)
It has a large area of distribution by the southeast asia, so it is a highly variable species, both in appearance and resistance to cold. Its general appearance is that of a small plant, less than 90cm tall, with slightly bluish light green leaves. In tropical climates they can reach larger sizes. However, you can find wild specimens with very dark, almost black petioles, from which numerous cultivars have been obtained. It produces many stolons, forming groups of plants very close to each other. As a species, it can also reproduce from seeds. They will normally withstand temperatures close to -5ºC, drying the aerial part as soon as it frosts or frost and going to rest. Tolerates waterlogged soils during the growing season.
This species is edible, but unless you grow it specifically for that, I do not recommend consuming it, and even less those that are sold in nurseries as an ornamental plant. The reason for this is not only the pesticides that it can carry, but it can also be hybridized with another colocasia that is inedible and present some toxicity.
There seem to be doubts as to whether it is a hybrid or a simple cultivar of colocasia esculenta. What is clear is that it is a spectacular plant, with all the aerial part purple, almost black. Its growth is the same as that of colocasia esculenta, varying only the color. Its biggest problem is that it comes from tropical populations and was obtained in Hawaii, so its resistance to cold is very low. In frosty areas, it is recommended to store it in a greenhouse when the cold weather arrives and not to water it until temperatures rise again. It can only be reproduced by stolons, since although it produces seeds, what germinates will not be identical to the mother plant and therefore it will not be correct to call it 'Black coral'. It differs from other black colocasias, such as colocasia esculenta 'Black magic' for being very bright.
Sometimes considered of a different gender, leukocasia, named for its white spathes. It seems that nowadays the accepted name is Leukocasia gigantea, because it is closer to Alocasia that colocasia. It grows to more than 2m tall, with more vertical leaves than the rest of the colocasias. The leaf blade is very rounded and follows the direction of the petiole instead of curving with the tip pointing downwards. The inflorescences appear in groups and have a thick white spathe that surrounds the spadix, as in alocasias. They do not produce stolons, but they do produce the occasional bulb. Even so, the best way to reproduce them is through seeds. It seems to support up to -5ºC, but it is very given to rot when it is in torpor.
There is a cultivar called 'Thailand giant' that reaches monumental dimensions, with leaf blades about 2m long and more than 1m wide. This cultivar can fetch great prices and is highly sought after by collectors.
The collocasia most resistant to cold, widely used in false tropical gardens as ground covers. It is not clear whether it is a hybrid or a cultivar of alocasia esculenta. It is a small plant that does not usually exceed 1m in height, generally less than half a meter. In climates with frosts it does not usually flower, but it produces many stolons with which it is easy to reproduce. It has light green leaf blades and pink petioles. Withstands temperatures below -15ºC as long as the substrate is kept relatively dry. It can survive lower temperatures if the ground is covered with a good layer of straw.
colocasia esculenta 'White lava'
Another cultivar obtained in Hawaii and therefore very little cold resistant. It is one of the most colorful colocasias, with purple petioles and very rounded blades, with wavy edges. These blades are green, with the veins marked in white, especially the main one, which also has a pink spot at the junction of the petiole. The size and type of growth is typical of Colocasia esculenta.
What do you think of the species of this genus? They give the same tropical air as alocasias but work much better in frosty climates. I invite you to try to grow any of these plants always outdoors, they can give you a very good result.
