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ORCHID CULTURE If you've already read the FAQs and my views in the Introduction or are just keen to get going, then the following information is intended as a guide to growing orchids. This information is actually the basics for successfully growing any type of indoor plant. Separate information is available on Potting. LIGHT Light is one of the most important factors to consider when growing plants and is often the most limiting requirement when plants are being grown indoors. It is also one of the most difficult matters to quantify and describe. Light meters are the solution but these are often beyond the scope of someone who wants to try a few plants so let's not complicate the issue. A good guide to whether or not a position is bright enough is to look at existing plants and see how well they are growing. As a rough rule of thumb, houseplants with large, broad leaves are those that naturally grow in shade either on low tree branches or on the forest floor. These are satisfied by low light levels. Plants that grow in full sun usually have smaller leaves that are not so likely to get scorched and these plants are rarely satisfied by low light. You may have suffered from a scorched and burnt leaf on a plant in direct sun. Windowsills can provide good growing positions but not all windowsills are the same. The direction is important. A South facing window will almost always be brighter than a North facing one unless the North window is considerably larger. Observe your windows and look at the orientation of the sun at different times of day. Make a note of which windows get the most hours of light and also which receive direct sun. Consider what the light will be like in winter. A window that is dim in summer can only be more so in winter. Similarly, a window that is bright in winter may receive direct, midday sun in summer. Direct sun is not all bad, it just depends on how much reaches the sill, at what time of day and what type of plants you want to grow. Direct sun in the morning or evening is not going to be as strong as during the day. If your windowsills are just a little too dark you can consider painting the sills and surrounding area a lighter shade or even white. Paler colours will always reflect more light around the plants and into the room. If a windowsill is very bright and direct summer sun scorches plants then some shading can be provided. This shading can take the form of netting or even a sun-loving plant close to the glass that will filter the light. Or, simply move the plant further into the room during the brighter summer months and move closer to the window in winter. Plants can have summer and winter quarters. If you don't want to clutter your windows or if you have large windows that let lots of light into a room then plants can be accommodated on shelves, tables and units inside the room. The same basic rules apply and the observation of light levels at different times of day and year should be considered. TEMPERATURE Temperature is another considerably limiting factor although it is also one that is actually far easier to control indoors when compared to a conservatory or glasshouse where sun makes the temperature fluctuate. The first mistake that is often made is to locate plants on or near to radiators and heaters assuming that the plants will enjoy the heat. They won't. Plants should be located where they will not be exposed to fluctuating temperatures or extremes of temperature. Orchids need more or less constant temperatures (cooler at night is fine) and those temperatures need not be high. If your house is not heated in the winter then the range of plants that can be grown will be considerably lower than if it does have heating. Most houses have a constant temperature during the winter due to thermostat controlled heating but the temperature can fluctuate during the summer where cooling is rarely available in hot weather. Rooms where winter heating is not provided should be avoided. A drop in temperature at night is acceptable and in many cases mimics conditions in nature but attention must be paid to overnight windowsill temperatures. Windowsills can become very cold during the winter months. Curtains are usually closed at night and they cut off the warmer air inside the room so that the air on the sill is cooled by the colder air outside the window. Glass offers very little insulation against the cold. This is rarely a problem in summer but must be carefully considered in winter. It may be necessary to move the plants further into the room each night or if not practical, consider moving them for the duration of the winter. If in doubt about winter temperatures on sills then a maximum-minimum thermometer purchased from a garden centre will soon provide the answers. Or, simply put a tea cup or glass in the window overnight and feel the temperature when the curtains are first opened next morning. Is it cold to the touch? If so, it will probably be too cold for the plant. A quick blast of cold such as when a door or window are briefly opened in winter are unlikely to do any harm but long term exposure to cold draughts should be avoided. WATER Water is actually easier to get right than is thought but the preferences of individual plants and the conditions the plants are in will determine the correct regime. Plants should be watered on an individual basis according to their specific needs. Some like to be moist at all times but most prefer to dry out completely between watering. These individual requirements should be catered for. Freshly potted plants will benefit from being watered little and often as they establish new roots but otherwise plants should be watered generously. The pots should be placed in saucers or trays of gravel so that they do not stand in the excess water. Waterlogged roots rot very quickly. This moist gravel also creates some humidity as the water evaporates. If gravel trays are not used then the excess water must be removed as soon as possible after watering. The "open" nature of the compost allows most of the water applied to run straight through the pot, just wetting the roots and the potting mix. This is normal and mimics rainfall where plants would be growing on trees. No attempt should be made to block the drainage hole or in any way slow up the drainage of the pot. If a drainage hole becomes blocked then the obstruction must be removed as soon as possible. Judging when a plant needs water is not difficult as long as care is taken. The potting mixture should be inspected and sometimes lifting the pot causes water drops to fall out of the drainage holes even though the surface is dry. If in doubt, withhold the water. All plants are capable of withstanding a degree of drought so a couple of extra days will do no harm. Overwatering however, can be damaging and rotting roots and sour compost will result. Water that has been drawn from a tap and then been allowed to rise to room temperature is better than cold mains water, especially in winter. Rainwater is good but is not essential. More regular watering will be required when temperatures are higher such as in summer. Some plants only need watering once a week during the winter months. HUMIDITY Humidity (water vapour) is harder to create effectively indoors when compared to under glass but it can be addressed. The commonest method is to place the pot on gravel in a tray or saucer which is significantly larger than the plant pot. This gravel will become moist from the excess water draining out of the pot when watering takes place and this water slowly evaporates. The gravel gives the water a greater surface area to cover and prevents the bottom of the pot from filling with water. Humidity can also be increased by adding small amounts of coconut fibre (coir) to the top of the compost and this holds a little moisture that is slowly given off. Moss is also good for this but it must be used sparingly. These materials are best used in the summer when the plants require more humidity and when the higher temperatures allow the moisture to quickly evaporate. In winter they may become sodden and cold, thus leading to root rot. A regular spraying of the whole plant with a fine mist spray is also beneficial. FERTILISER Fertilisers should not be added to the compost of epiphytes. Water soluble fertilisers should be used and they should be used at half the manufacturers recommended strength. Orchids are quite sensitive to fertilisers so these weak mixtures are best. Fertiliser can be applied up to twice a week but should only be given when the plants are actively growing. If there is no new growth of either leaves or roots then there is no need to feed. Fertiliser should not be poured onto the crown of the plant but onto the roots and potting mix. A foliar feed can also be applied with a sprayer with the mixture being sprayed onto the leaves and also the roots. There are culture sheets available from the "American Orchid Society" AOS. Here you will find the latest culture sheets for most popular cultivated orchid genera. These informative pages feature the beautiful line drawings of the late Marion Sheehan. |
