Orchids 101: a complete guide to keeping indoor orchids alive
Phalaenopsis, or moth orchids, are one of the longest flowering orchids for indoors, but light levels are important. "The more light, the better," says Don O'Connor of the nursery Gellert's, which specialises in houseplants, "Not direct light through glass as this can burn them. But a little bit of early morning sun is OK."
Too much light and their dark green leaves will begin to fade. Too little light and the plant won't flower, and foliage will become limp. An east-facing window (behind net curtains) is ideal, although shading from 10am to 5pm will be needed in summer.
Moth orchids need regular watering, enough so that they don't dry out between applications. "In summer, about twice a week but never let them sit in water," says Don. "In winter, every seven to 10 days depending on how warm the house is. A good indication they're not getting enough water is when new buds go yellow and fall off."
Moth orchids also need humidity. Unlike many other types of orchids, they have no pseudobulbs to store water. But they do store some water in their leaves. If the air is constantly dry, the water will evaporate and the leaves will wilt. To increase humidity levels, place plant pots on pebbles in a saucer of water.
With feeding, little and often is best, so incorporate your fertiliser in with your watering. Use an orchid food from spring through summer. Once a month, flush the plant thoroughly with straight water to remove any salt build-up from the fertiliser.
Moth orchids send up new flower spikes when the temperature drops in autumn, says Don. "You can fool them into thinking it is autumn by moving them into a cooler position. This is how we flower them all year round in the nursery."
When the flowers on a spike are finished, cut the spike back. "A shortcut for reflowering is to cut the old flower spike just above two nodes up from the base," says Don. "They will send out new growth from this point, rather than waiting for a new flower spike in autumn."
The most hybridised orchid in the world, cattleyas are known for their large, showy flowers and are often referred to as the queen of orchids. Cattleyas need good light to flower well, but avoid direct sunlight. "Aim for strong, light green leaves," says Ross Tucker of Tuckers Orchid Nursery. They are happy with a minimum night temperature of 12°C and can cope up to 35°C. "Like all orchids, they do best with plenty of air movement. A small fan can be used if growing indoors or in a glasshouse. This helps to prevent many fungal diseases. During the summer they would prefer to be outside if at all possible."
Cattleya can flower two to three times a year, but they must have good light. "I can't emphasise enough how important good light is. With the right light levels, your flower stem will raise clear from the foliage and the individual flowers will present themselves 360° around the stem rather than be clumped on one side." The first sign of a new flower stem is usually the sheath emerging from the top of the cane. "Cut the top 3-5mm off the sheath once you see the buds within. This prevents them sweating and rotting. Stake your growths with sheaths on early to present your flowers for the best display."
Cattleyas like regular summer watering, but they need a period of dryness too, so ensure the plant is dry before watering again. Incorporate an orchid fertiliser into your watering regime. "Up to twice a week in summer and once every two weeks in winter." They also like a rest after flowering, so at that time keep watering to a minimum and stop feeding for a few weeks. When you see new roots, gradually increase feeding and watering. Flush with plain water between feeds.
Sometimes, scale insects hide beneath the dry sheaths around the pseudobulbs. "A spray of Conqueror oil in water, repeated regularly, will keep them under control. After an oil spray, keep the plants shaded as the oil on the leaves can burn if the light levels are too high. After a couple of waterings, the light levels can go back to normal as the oil washes off the leaves."
Oncidiums, or dancing ladies, are one of the largest orchid genera, comprising some 750 species. Their growth habit varies considerably. Plants may grow from just a few centimetres to more than a metre in height. The number of flowers also varies, as does the colour range, although yellow and brown are the most dominant hues. Oncidiums like similar conditions to cymbidiums. They like an average night temperature of around 12°C, and humidity of about 60 per cent, as well as good air circulation or ventilation without cold draughts. Humidity may be increased by placing pots on saucers filled with pebbles and water.
As a general rule, oncidiums should be given plenty of light (not direct sunlight) or flowering will be inhibited. The more light, the more scent too. "Leaf colour should be light green and sometimes may even have a pinkish tinge," says Ross Tucker. A dark green indicates not enough light; too much red in the leaves indicates too much light. Oncidiums like to become reasonably dry between waterings. "They love it when there is a rapid alternation of wet and dry conditions," says Ross. "For this reason they often do well grown on slabs where they can be watered daily and dry rapidly." These plants are not heavy feeders. They should be fed at least once a month, although diluted orchid food may be applied weekly while plants are actively growing.
Most oncidiums require a short rest period from water and feeding after flowering. Repotting should take place at least every second year. "Perforated plastic pots or clay pots are ideal as the roots can dry quickly, preventing spotting of the flowers and leaves," says Ross. "Keep the pots on the small side. Bark mixes are usually satisfactory."
Cymbidiums are one of the easiest orchids to start out with. They can be grown outdoors in frost-free areas, or indoors in a well-lit room. In an ideal situation, night temperatures should be between 10°C and 15°C, although they tolerate temperatures as low as 5°C. If it gets as low as this, keep your plants on the dry side.
Cymbidiums need good light to flower well, but not direct sunlight, or the leaves will burn. If your cymbidium doesn't flower, it's often because it doesn't have enough light. Position it so that it gets as much sunlight as possible without being in the burning sun. Approximately 25 per cent shade is ideal.
Cymbidiums are fast growing, and as such are heavy feeders. They need feeding 12 months of the year. A weekly feed with a specialised orchid food during the growing period (from January until flowering) is ideal. Blood and bone or a slow-release fertiliser can be used after that.
Mature plants are best repotted in spring, every 2-3 years, after flowering. As old potting mix breaks down, it tends to hold more water, which can encourage root rot. Remove the plant from the container, gently rub away the old potting mix, and discard any damaged or unhealthy looking pseudobulbs (a pseudobulb will have a thickening at the base of the stem).
Sometimes leafless bulbs appear at the centre of the plant. Discard these too. Use the same container and refill with fresh orchid mix.
You can divide and replant single pseudobulbs (the base of the bulbs should be at the top of the mix), but they will take around three years to flower. After repotting, water well and feed with orchid food.
The slipper orchid can be broadly divided into two groups: those with uniformly green leaves which prefer cooler temperatures (minimum 10°C to a maximum of between 21°C and 27°C) and those with mottled leaves which prefer warmer conditions (minimum temperature between 15°C and 19°C). However, paphs have a wide tolerance range and in general, minimum night temp of about 12°C will suit most of them, says Ross Tucker. "Young plants will grow better with higher night temperatures of about 18°C to 20°C."
Paphs do best with about 60 per cent shade, with a little more shade for young or weak plants. "If your plants have very pale green leaves, they may be getting too much light and direct sunlight can burn the leaves. Too little light may result in dark green leaves and no flowers." Paphs have no pseudobulbs to store water, so require constant moisture throughout the year. "The frequency of watering will depend on the season, but the secret is to ensure that the compost is always damp but never soggy," says Ross. "The roots will die if they are constantly saturated, but equally dire results will occur if they dry out too much. Watering early in the day is recommended so that any water in the leaf axils can dry by nightfall to avoid the risk of rotting."
Feed with an orchid food. A little slow-release fertiliser can also be used. "Sprinkle with dolomite every six months for best results as they do not like acidic mixes," says Ross. Repot yearly after flowering, or leave no longer than two years. "Paphs have very brittle roots that break easily so treat them gently. The roots can be difficult to bend so be careful putting them back into the pot, but do try to keep them in the smallest possible pot the roots will fit into."
For the most amazing scent, try growing a zygopetalum. These spotted orchids have a musky perfume that permeates an indoor space for many weeks. Flower spikes hold four to seven blooms and plants can flower twice a year in spring and autumn.Zygopetalums like a fairly bright light, out of indirect sunlight, with a minimum night temperature of 10°C-12°C.
When plants are actively growing – during the cooler seasons – water and feed regularly. Avoid wetting the leaves, or spots will form. When they've finished growing – towards the end of summer – cut back on the watering. Just keep the mix damp – never soggy – until new growth emerges.Water when the potting mix has dried out and feed fortnightly.
Zygopetalums have thick, fleshy roots and like a bit of room to grow. If they look as though they're becoming pot bound, replant in a bigger pot in late summer. Go about this task with care. The roots break fairly easily. Aim to repot every two years.
These Aussies are well suited to cooler temperatures. The common mauve or white Dendrobium kingianum can be seen growing on trees around Sydney, Adelaide and Melbourne; Dendrobium speciosum grows on rocks and cliff faces in the warmer climates of New South Wales and Victoria. Both can fill a room with glorious scent. Most Aussie dendrobiums grow best in cool to intermediate temperatures, between 5°C and 25°C, although Dendrobium lawesii, Dendrobium speciosum and its hybrids like it slightly warmer.
Dendrobiums enjoy a high light level, and Dendrobium speciosum and kingianum can be grown in full sun. But if you're bringing home a new plant from a nursery, introduce it to sun gradually so you don't burn the leaves. During winter, maximum light levels will encourage better flowering. Flower spikes appear around July or August, with flowering in spring. Bear in mind, though, that dendrobiums are slow-growing and don't usually flower until they are about eight years old.
Feed and water regularly during the growing season, but let the roots dry out slightly between watering. Too much watering and high nitrogen fertilisers can encourage keikis (baby plants) to form on the canes at the expense of flowers. Repot plants in December and January every two years.
- NZ Gardener