The secret of orchids
Orchids make up one of the biggest families of flowering plants. They have recently replaced poinsettias as the most popular potted plant world-wide. With their astonishing beauty and magnificent colouring that give us astonishing contrasts and a never-ending range of tones, they make very popular plants to grow and enjoy in our homes. Scents can range from delightfully aromatic to fleeting and barely noticeable, and blooming periods can last several months.
Epiphytic orchids comprise the vast majority of tropical orchids available for purchase in commercial greenhouses and orchid-specialty outlets. Most orchids grown in the home are epiphytes or air plants. This type of orchid makes the best houseplant and affords much satisfaction and pleasure.
Orchids have a unique plant structure. By understanding how the plant functions, one can associate the cultural conditions required in order for the orchid to thrive. Their requirements for light, moisture, humidity and fertilizer can be different from common houseplants, but different does not necessarily mean difficult!
Orchids have two basic growth patterns: sympodial growth originates from a lateral shoot from the rhizome so the plant spreads in a horizontal direction, monopodial growth originates from a terminal shoot and the plant grows in a vertical direction. This is an important consideration when you are dividing and repotting your orchid.
It's important to understand the principal features of epiphytic orchids, including roots, pseudobulbs and leaves, when considering growing them in the home.
Roots of any plant play an important role in anchoring the plant as well as in providing nutrition. Orchid roots
also perform functions that include storage, respiration and even photosynthesis. In sympodial orchids, the roots develop from the rhizome located just under the surface of the growing medium, and in monopodial orchids the roots emerge from the stem and often grow at right angles to the leaf. The healthier the roots, the greater the potential to gather minerals, salts, and moisture from the environment. In summary, a healthy orchid starts with healthy roots.
Orchid roots have a covering of grey-green dead cells called velamen that cover the whole root and are found behind the green growing tip of the root. Velamen soaks up moisture very quickly and also plays an important part in respiration as it allows the plant to take up oxygen as the velamen dries. If velamen is soaked with water too long it undergoes bacterial fermentation and will be destroyed. In order to maintain healthy roots it is important to have a sufficient interval between waterings, good drainage for the pot and a growing medium that provides adequate aeration of roots inside the pot.
Many orchids produce pseudobulbs or false bulbs, which grow above the surface of the growing medium from the rhizome every year. Leaves and flower spikes emerge from the pseudobulb, which is made up of fibrous material that can store a great deal of moisture and energy. Pseudobulbs, found in many different shapes and sizes, are the longest living part of the orchid and will survive in a leafless, dormant state for a long period of time. In order to maintain healthy roots it is important to have a sufficient interval between waterings, good drainage for the pot and a growing medium that provides adequate aeration of roots inside the pot.
Most orchids grow a relatively small number of leaves in a wide variety of forms. Leaves can be succulent and become a storage organ for water. Leaves contain tiny openings on the underside called stomata that can open widely when the temperature rises to allow evaporation and cooling and prevent an excessive increase of internal temperature. Narrow cylindrical leaves, such as those of a Vanda orchid, do not store heat efficiently so the plant will thrive in direct sunshine and a warm environment. Some species of orchids are deciduous. Their leaves will turn yellow and drop to leave a leafless pseudobulb which can act as a storage organ for new shoots.
Leaf structure and appearance are indications for orchid culture. The thicker the leaf, the less often the plant requires watering. If leaves are deciduous, the plant will require a rest period. If leaves are tender and persistent, the plant requires uninterrupted watering. If leaves are cylindrical, the plant can be exposed to long periods of full sun.
Growing Orchids Indoors
Growing orchids indoors requires attention to light, temperature, humidity, air movement, watering and type of growing medium.
Different types of orchids have different light requirements, ranging from low, to medium and high; however, all orchids grow and bloom best in as much light as they can tolerate without burning. Plants with thick leaves are slow to burn and plants with thin leaves burn more easily.
The best location for growing orchids in the home is the brightest spot, and window-sills often provide ideal locations. East-facing windows are ideal. South-facing windows receive bright light for most of the day, but growers should use caution in summer because the bright light may burn plants. Sheer curtains will help to diffuse light during the summer. West-facing windows may work well and a north-facing window may work for an orchid that requires low light. The direction the window faces is only a general indication as to the quality of light it offers as some windows are shaded by outdoor plants, building overhangs, etc.
When orchids are receiving a correct level of light, their leaves will be a medium olive green and the pseudobulbs will be firm and full. Leaves on orchids receiving too much light may be scorched or have a yellowish or reddish tinge. Too little light may be demonstrated by dark green leaves and soft or shrivelled pseudobulbs.
Many types of orchids thrive under artificial lighting. Consider adjusting the length of light during the day to coincide with the seasons, as some orchids come into flower only with periods of longer daylight.
Orchids are adapted to temperature fluctuations. Without day/night fluctuations of approximately 10 degrees, the plant may grow well, but does not flower. Cool nighttime temperatures allow them to store the carbohydrates required to produce flower spikes. Essentially orchids may be classified into warm, intermediate or cool growers. Warm growers prefer 26 to 32 degrees C during the day and 18 to 21 at night. Intermediate growers like 21 to 26 degrees C during the day and 5 to 18 at night. Cool growers thrive at 15 to 21 degrees C during the day and 10 to 13 at night.
Be alert for hot drafts from electrical motors or cold drafts from open doorways, etc.
Most orchids like a daytime humidity of 40 to 70 per cent. Hygrometers are quite reliable to measure humidity in your growing area. Placing plants on water-filled trays of pebbles is an excellent method of increasing humidity surrounding a plant. Ensure the water level is not high enough to saturate the bottom of the plant pots. There are a variety of humidity tray designs available.
Plants are excellent self-humidifiers when they are arranged in groups. Misting provides humidity for a short time but should not be applied to the orchid blooms. Misting in the morning allows the plant to dry before nightfall and discourages the growth of mold on damp plants.
All orchids love gentle air movement as it helps to regulate plant temperature, allows plant roots and leaves to dry, and it discourages the growth of mold and other plant pests. Air movement prevents cool air pockets from forming next to window panes in winter. Many homes have ceiling fans attached to light fixtures, and these work very well. If using a small portable fan, aim the fan away from the plants and allow the air being pulled into the fan to circulate among the plants. The air coming out of the fan will dry out the plants. Gentle breezes help to reduce pests and encourage healthy growth.
Watering and Fertilizing
Overwatering is the most common cause of orchid root loss. After watering, the growing medium will retain humidity for hours and even days, promoting good root growth and health. Allow plants to drain. The watering schedule will depend on the type of growing medium, pot type and size, temperature, season, amount of air movement, type of orchid, etc.
The smaller the pot size, the higher the temperature. The coarser the growing medium, the lower the humidity. The greater the amount of air movement, the more often watering will be required. Watering may be needed weekly or more often.
Rain water is ideal for orchids. The quality of tap water varies in different areas. Essentially tap water with an excess of chlorine, or which has been artificially softened or contains high amounts of calcium may harm the orchids. Water should be room temperature and watering should be done in the morning, so the plant’s leaves and shoots have time to dry before dark.
Orchids do better with too little fertilizer than too much. The recommendations for fertilizing vary from source to source. It is agreed however that orchids should be fed with a weak dilution of fertilizer. If using a general fertilizer, quarter strength is recommended. Flushing the growing medium with clear water will help to remove any accumulated fertilizer salts from previous applications.
Containers and Potting Medium
Orchids should be grown in as small a pot as possible as long as there is space for the roots. Overpotting leads to overwatering with subsequent root rot. Pots with good drainage are essential. Plastic pots are lightweight,
easy to clean and relatively inexpensive. Clay pots dry out more quickly, are not lightweight and are more expensive. Wooden baskets allow space for root growth, but do not hold moisture well. Orchids may also be mounted on slabs of bark to demonstrate the way they would grow in the wild.
Orchids should be repotted every couple of years, when the potting medium starts to deteriorate, when the orchid looks like it is being stressed or when the plant needs to be divided. A wide variety of potting mediums are available. Different types of medium work for different home environments.
An ideal orchid medium should allow air to circulate and water to flow freely around the roots. It should withstand decomposition for as long as possible and provide structure onto which the roots can adhere, and it should discourage the growth of microbes. Sphagnum moss may be used by itself or more often as an additive to other potting mediums. It has antiseptic and vitalizing properties and holds moisture longer than some other mediums.
Fir bark is available as a fine, medium or coarse grade. Generally, the smaller the diameter of the orchid roots, the finer the grade of bark that should be used. Orchids with large roots do well in a coarse bark mixture.
Charcoal absorbs acids and is a common ingredient of potting mixes. It also collects salts that are dissolved in water. Perlite helps the medium to retain water and it does not degrade. Many commercial orchid potting mixes are made up of a variety of these products. Other mediums are available including clay pellets which hold moisture and do not degrade. It is good to experiment to find the potting medium that works best for your growing conditions.
Orchid culture in the home is a very attainable goal. Choose a plant that will thrive in your home environment. Success can be achieved by understanding your plant’s characteristics, providing suitable lighting and implementing a few elementary precautions as described here to achieve spectacular results. Keep trying until you find what works for you. Once you have mastered the culture of a specific type of orchid (and you will), it is time to try a different variety.
Joan Porteous is the president of the Manitoba Orchid Society. Part one of a two part series. Next issue: What orchids to shop for.
Orchid potting mediums include fir bark, sphagnum moss, charcoal, perlite and clay pellets.