HOW TO GROW AND CARE FOR OUR PLANTS
THE Coleus they are plants native to the tropical areas of Africa and Asia and are highly appreciated and cultivated for the beauty of their leaves.
Coleus - Plectranthus
Species: see the paragraph on "Main species"
The genre Coleus belongs to family of Lamiceaeand includes more than 150 species.
From their appearance some species resemble the mint and thenettle, also belonging to the family of Lamiaceae, despite not having the characteristics of those genres.
THE Coleus they are plants that, in the apartment, do not reach large dimensions and do not exceed 50 cm in height while in their natural environments they can exceed one meter in height. They are evergreen perennial plants but are generally grown as annuals.
They own a stem quadrangular section and the leaves they take on very different shapes depending on the species: heart-shaped, lanceolate, oval, with smooth or serrated edges and with colors ranging from light green, to copper, to red, to orange and yellow, combined in various ways.
THE flowers they are gathered in spike inflorescences and are small, varying in color from white, to blue, to purple, not very showy.
There are many species of Coleus but the most important from which almost all the cultivars that we find on the market are derived is theColeusblumei.
Coleus blumei it is native to the island of Java and in nature it is a shrub that reaches one meter in height. The leaves are pale green, oval, with jagged edges and variously streaked with purple or coppery bands.
Almost all the cultivars that we find on the market are derived from this plant, among which we remember: Coleus blumei 'Carefree'with palmato-labiate leaves, dark red in the center and green at the edges; Coleus blumei'Rainbow'with large crimson leaves with dark red veins and almost black red margins; Coleus blumei 'Saber'bushy habit with leaves streaked with red, yellow and green.
The plant of Coleus thyrsoides it has heart-shaped leaves and its peculiarity compared to the other species is to have an abundant flowering from November to March, producing very pretty blue flowers, very decorative gathered in panicles. It is a plant that can reach even one meter in height.
The plant of Coleus verschaffeltii it has typically heart-shaped leaves, with indented margins and the leaf plate covered by a light down and variously streaked with red with red margins.
Compared to Coleus blumei it is a plant that reaches larger dimensions.
The genre Coleus it includes plants that are not difficult to cultivate if one considers that they are plants of tropical origin for which they cannot be grown under certain minimum temperatures.
The Coleus loves the light therefore it must be exposed in the brightest position of the house preferably to the south. It can also be kept in direct sunlight as long as it is protected during the hours of greatest sunshine so as not to cause burns to the leaves. The bright and varied coloring of the leaves is directly proportional to the amount of light they receive.
The optimal cultivation temperatures are around 20-25 ° C but they also tolerate higher temperatures well. It is advisable that the levels below which the plant dies do not fall below 12-13 ° C and it is for this reason that in temperate climates the plant is bred as an annual as it does not survive the winters especially if grown outdoors.
Beware of cold drafts that are not tolerated.
At the end of the summer, the plant begins to lose the lower leaves leaving uncovered stems. We don't have to worry about that, they will grow back in the spring. In any case, it is also for this reason that they are often raised as annuals: it is preferred to renew the plant given its low cost.
From spring and throughout the summer the plant of Coleus it should be watered abundantly so that the soil remains constantly humid (not wet) and without leaving stagnant water in the saucer.
During the winter, water with more moderation, always keeping the soil slightly humid.
THE Coleus they love humid environments so it is advisable to nebulize the leaves regularly early in the morning to avoid water droplets concentrating the sun's rays during the hottest hours, functioning as lenses.
If grown outdoors, at the time of arrangement, take care not to place it in correspondence with depressions in the ground where both rainwater and irrigation water could accumulate.
It is necessary to be very careful, if the temperatures drop, not to let the water stagnate. This would lead to an excessive lowering of the temperature at the root level which could be fatal for the plant.
TYPE OF SOIL - REPOT
Since generally the plant of Coleus it is bred as an annual, usually there is no mention of repotting.
In any case, a good soil is essential for this plant to ensure a thriving growth. The first thing to keep in mind is that it must have as its primary characteristic the possibility of allowing a rapid drainage of excess water. Do not use acid-reacting soils but neutral or slightly alkaline.
A mixture could be made up as follows: 1 part of fertile soil, 1 part of peat, 1 sand. Heavy, clayey soils that retain too much water which causes stagnation, very dangerous for this species, are to be avoided.
Personally, I always recommend using clay pots even though many opt for plastic pots (less expensive and more drainage holes). I believe that the terracotta ones allow the earth to breathe and if the drainage hole has been arranged in such a way as to guarantee a good drainage of the water, well, I would say that it is perfect.
If the plant of Coleus it is planted outdoors and you are dealing with a clayey soil, make sure before the planting to dig and mix the soil with sand (about 30%) to improve drainage.
From spring and throughout the summer fertilize the Coleus every 2 weeks with a liquid fertilizer to be diluted in the irrigation water by slightly decreasing the doses compared to what is written on the package. During autumn and winter the fertilizations must be suspended.
Use a fertilizer equally balanced in nitrogen (N), phosphorus (P), potassium (K) also contain the so-called microelements, that is to say those compounds which the plant needs in minimal quantity (but still needs it) such as magnesium ( Mg), iron (Fe), manganese (Mn), copper (Cu), zinc (Zn), boron (B), molybdenum (Mo), all important for a correct and balanced growth of the plant.
The plant ofColeus it is certainly not cultivated for the beauty of its flowers therefore when they begin to appear, it is advisable to eliminate them in order not to make the plant "waste" energy by cutting them, as soon as they appear, under the first couple of leaves.
A recommendation that I will never tire of repeating: sterilize, possibly by flame, the shears you use to cut especially when you switch from one plant to another. If, on the other hand, you do it with your hands, well, take care that they are well cleaned.
For plants of Coleus we cannot speak of real pruning but of topping, that is to say cutting the vegetative apexes of the branches as soon as they tend to disperse in order to stimulate the plant to produce new branches and therefore obtain a more compact looking plant.
Even in the case of topping I will never tire of repeating it: sterilize, possibly with the flame, the shears you use to cut especially when you pass from one plant to another. If, on the other hand, you do it with your hands, well, make sure they are clean.
The plant of Coleus it multiplies by cutting or by seed.
In choosing the technique to be adopted, it must be borne in mind that multiplication by seed has the disadvantage that, when genetic variability takes over, it is not certain that plants will be identical to the mother plants, in which case if you want to obtain a well-defined plant or not. if you are sure of the quality of the seed you are using, it is good to do the multiplication by cuttings.
MULTIPLICATION FOR TALEA
The cutting can be taken from the new shoots between April and September about 7-10 cm long.
The cuttings should be cut immediately below the node so that 2-3 leaves remain and eliminating the lower leaves. Also choose them from robust and healthy Coleus.
It is recommended to cut with a razor blade or a sharp knife to avoid fraying of the fabrics, taking care that the tool used for cutting is clean and disinfected (preferably with a flame) to avoid infecting fabrics.
After removing the lower leaves, the cut part is immersed in a rhizogenic powder to facilitate rooting.
Subsequently, the cuttings are arranged in a compound formed by a part of dark peat and a coarse sand. Make a hole with a pencil and place it at a depth of 1.5-2 cm, then take care to gently compact the soil.
The pot is placed in an airy and shady environment at a temperature of around 21 ° C, taking care to keep the soil always slightly moist (always water without wetting the rooting plant with water at room temperature).
Once the roots start to appear it means that the Coleus plant has rooted at which point the plant moves to a brighter position (not in direct sun). When the seedlings are large enough to be handled without problems, they are transplanted into the final pot in a compost as indicated for adult plants and treated as such.
MULTIPLICATION BY SEEDS
The seeds of Coleus must be sown in January-February in a compost formed by a part of fertile soil and a coarse sand or perlite or vemiculite and must be buried very little (2 mm).
The tray containing the seeds should be kept in the light, at a temperature as constant as possible around 21 ° C. It is essential that the soil is constantly moist (use a sprayer to completely moisten the soil) until the moment of germination.
It would be a good idea, to prevent any attacks by fungi, to administer a broad spectrum fungicide with the irrigation water, in the doses indicated in the package.
The tray must be covered with a transparent plastic sheet (or with a glass plate) which will guarantee a good temperature and will avoid a too rapid drying of the soil. The plastic sheet must be removed every day to check the degree of humidity in the soil and remove condensation.
Once the seeds have germinated (the time varies from a few weeks to a few months), the plastic sheet is removed and the box is moved to a brighter position (not direct sun).
Among all the plants born, surely there will be those less vigorous than others. Identify and eliminate them in this way you will guarantee more space for the most robust plants.When they are large enough to be handled, you will transplant them, in any case being very careful not to spoil any part of the plant (it would be preferable to use a fork for these operations that you will insert under the ground to take the whole seedling and put it in the new pot) in a soil as indicated for adult plants and treat them as such.
PARASITES AND DISEASES
The Coleus it can be subject to various pathologies, more dictated by a bad cultivation technique than to real parasitic diseases. In any case, the pathologies that can be encountered are the following:
The leaves turn yellow and wither
This symptomatology is to be attributed to low environmental humidity and scarce irrigation.
Remedies: make sure that the soil remains constantly humid and spray the leaves regularly as indicated in the previous paragraphs.
Dark, wrinkled rings form along the stem
This symptomatology can be the prelude to rot due to excessive watering.
Remedies: if the soil is too wet, let it dry. Remove the damaged parts. Treat the roots with a broad spectrum fungicidal powder. Wait 7-10 days before watering and better regulate irrigation for the future.
The plant grows little and does not produce new leaves during the growing season
This symptomatology can be attributed to nutritional deficiencies or poor lighting.
Remedies: make an analysis on how you have raised the plant up to that moment according to the indications given in the individual paragraphs and then adjust accordingly.
The leaves are discolored
This symptomatology is due to poor lighting.
Remedies: move the plant to a more suitable place.
Spots on the underside of the leaves
Spots on the underside of the leaves could mean that you are in presence of cochineal and in particular mealy cochineal. To be sure, it is recommended that you make use of a magnifying glass and observe yourself. Compare it with the photo on the side. They are features, you can't go wrong. Also if you try to remove them with a fingernail, they come off easily.
Remedies: remove them with a cotton swab soaked in alcohol or if the plant is large and potted, you can wash it with water and neutral soap, rubbing very gently with a sponge to remove the parasites, after which the plant is varisced very well to eliminate all the soap. For larger plants planted outdoors, you can use specific pesticides available from a good nurseryman.
Presence of small whitish animals on the plant
If you notice small white-yellowish-greenish mobile insects you are almost certainly in the presence of aphids or as they are commonly called lice.Observe them with a magnifying glass and compare them with the photo on the side, they are unmistakable, you can't go wrong.
Remedies: treat the plant with specific pesticides readily available from a good nurseryman.
There is a kind of Coleus, the Coleus forskohlii (photo below) which contains a substance, the foskolineused in Ayurvedic medicine to obtain various preparations used to combat muscle and stomach cramps, blood pressure, allergies, asthma and depression.
In addition to this, one of its characteristics is to promote weight loss. One of its characteristics is in fact that of increasing the concentration of the cAMP (cyclic AMP) inside the cells which is a cellular messenger that activates numerous enzymes including lipostatic ones, i.e. those that stimulate lipolysis and the release of lipids, thus increasing combustion. de-fat.
The use of this substance must however be done under strict medical supervision.
The name Coleus comes from the Greek koleos "Sheath, guiana" because of the filaments of the stamens which appear to be gathered in small bundles.