Friday, July 30, 2010

Calathea : how to grow these plants

The varieties of Calathea plants range in many leaf size, height, ornate patterns on leaves and colors. While cleaning efficiently the air we breathe they add beauty to the spectacular floral arrangements that combine heliconias, ginger, and ornamental banana flowers.

Calathea picturata cv argentea

The growing period of Calathea plants is from March to October. Fresh flowers for the vase are first cut at the base of the stem then re-cut to the desired lenght.

Temperature & Humidity
In Thailand they are preferably cultivated by gardeners in areas of the north-east where growth is easier and the leaf prints are more vibrant under the colder temperature there. Also temperature and humidity in these tropical places vary smoothly.

All Calathea are easy growers, they have the same general care requirements. They just need the proper care and correct room environment. Either outside or as indoor houseplant they should not be kept at temperatures under 16 degrees celsius ( 60 - 70
degrees Fahrenheit ), and most importantly high humidity is essential to all calathea sorts so that terrarium-type enclosures, or just plastic sheets may be required, at least for the first weeks. Humidity is one of the most important factors in having a Calathea plant flourish.
Lower than standard humidity levels can cause the tips of the leaves to brown, ( see
Calathea bella on the picture ) , appear dry or leaves fall from the plant; in arid conditions mites and scale will put the health of the plant at risk.

Some people report misting regularly to help maintain humidity levels but this method is also said to fail.

A better option for rooms without a greenhouse consists in placing the plant on a shallow container filled will pouzzolane or any other water retentive device. However the best device is undoubtedly an air humidifier to add moist air to the plant's environment.
Never should the roots of the plant be allowed to stand in water as this will inevitably cause root rot. Below
Calathea rosea - picta

Calathea plants require a soil that is well-draining and holds in moisture. A mixture of nutrient-rich soil and peat is the best mixture for the Calathea varieties.

keep the soil moist: a drooping plants or rot of the stem may indicate too much watering during the winter months. Curled leaves, spots or yellowing lower leaves are caused by insufficient watering. In winter the soil can be let dry out between waterings.

It should be moderate, but preferably not under 300 lux. Exposure to bright direct light can fade the colors or burn, scorch the foliage.

Rhizomes should be planted into a shallow soil and not disturbed for several months as the initial root growth would suffer. The original stem will not grow again, but as the plant creates new rhizomes new stems will develop underground.

There is no need to fertilize before the appearance of several new stems, then fertilize regularly in the growing season. Repot every year or every other year into new potting mix.

Propagation is by division at the time of repotting. The new divisions must be covered with a plastic dome.

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