Orchid Care and Orchid Cultivation

Here we deal with all aspects of orchid cultivation including indoor culture, and tell you how to make the most of these fascinating and beautiful plants.

Orchids under cultivation can be divided into three groups according to their temperature requirements. These comprise the cool, the intermediate and the hot growing types. The cool house orchids, that are more generally grown and usually recommended for the beginner, require a winter minimum night temperature of 10°C (50°F). This will rise by at least 5°C (10°F) during the daytime. Summer night-time temperatures will be approximately 3°C (5°F) higher, but be sure to keep daytime temperatures down to a maximum of 24°C (75°F).

Intermediate house orchids require temperatures at least 3°C (5°F) higher than the cool, while in the hot house, plants succeed well with a minimum night temperature of 18°C (65°F) winter and summer, and a correspondingly high daytime temperature.

It therefore follows that a cool greenhouse will require artificial heating during the autumn and winter months (end of September to early May), depending on the outside weather conditions. In the intermediate, and especially in the hot section, artificial heating will be required all the year round.

Ventilation and shading

Temperatures inside the greenhouse are controlled by ventilation and shading. Ventilation is most important to orchids, and fresh air, without a draught, should be applied at all times. During the winter, with cold, dull days and little or no sun, it may be possible only to open one ventilator just a crack for an hour or so. This will be sufficient to freshen up the air inside without causing a drop in temperature. During the summer months fresh air can be applied to the cool house almost permanently. It is far better to leave the ventilators open all night during very warm spells of weather than to allow the temperature to rise in the early morning before opening the ventilators. You must be a little more careful, however, in applying fresh air in the hotter houses, where a drop in temperature could be harmful. Small electric fans can work wonders in a small greenhouse, and will keep the air continually on the move without altering the required temperature. They can be used with equal advantage throughout the year, and are an important asset for people who have to be away from home all day. Automatic ventilators can be brought into play whenever required, taking much of the worry out of growing greenhouse orchids.

Orchids enjoy light, but cannot stand the direct burning sun that penetrates the glass during the summer months. However, take advantage of any bright sunny days that occur from mid autumn to early spring (September to February) to give the orchids full light without fear of burning. From mid spring (March) onwards and throughout the summer months, use some form of shading in the greenhouse. The ideal form of shading is roller blinds that can be attached to the outside of the glass, with a 25cm (9 in) gap between the blinds and the glass to allow for a cooling air flow. They can be rolled up and down as required, allowing the plants maximum light on sunless days. Apart from preventing scorching of the plants, the shading also assists in keeping the temperature down in summer. It may also be necessary to shade the glass with white paint that reflects the light.

Humidity and damping down

Humidity is perhaps the most important single factor in orchid culture. Remember that the plants thrive where humidity is naturally high, and they have evolved as epiphytes living more or less on nothing but humidity. The orchid greenhouse must therefore be damped down daily, until the floors, staging, and all parts of the house are thoroughly soaked. In the summer damp down two or three times daily, and spray the plants overhead once a day. Do this towards late afternoon, or when the sun is just passing over the greenhouse. Providing all foliage is dry by nightfall, the plants will enjoy their daily spraying. During the winter months damping down will probably be necessary only once a day, or every two days, depending upon the immediate weather conditions. The aim should always be to balance the temperature with the humidity. When the temperature is low on cold winter days, the humidity must also be low, and when the temperature is at its maximum on hot summer days, there should be maximum humidity to balance.

Don’t spray overhead during the winter as the water is cold and will remain on the foliage too long before drying up, leading to the appearance of damp marks. Soft-leaved plants such as the lycastes and also the paphiopedilums and phalaenopsis should not be sprayed at any time, since they are particularly prone to damp spots on the foliage. They do, however, require a humid atmosphere around them.

Damping down is carried out to create the humid growing conditions that orchids enjoy, but should not be confused with the actual watering of the plants: this is a separate routine procedure. Water with a spouted can, flooding the surface once or twice to wet the compost thoroughly. This should drain away immediately. Watering of orchids is carried out according to their growing cycle. During the summer months the orchids are growing at the maximum, new bulbs are being made and the plants are in their period of peak energy. This means they will consume copious supplies of water. The ideal is to maintain the compost in a constantly moist condition. Allowing the compost to become bone dry for any period will slow growth, while the other extreme of soaking it to the extent that it eventually becomes sodden, will lead to souring and loss of the plant roots.

During this summer growing period the orchids can also take limited amounts of artificial food; this can be in the form of a liquid food diluted and sprayed over the foliage, or given directly through the compost at regular 10-day intervals. Feeding should be gradually lessened towards the autumn and discontinued throughout the winter.

Rest periods

Many orchids rest during the winter months, when little or no activity is going on within the plants. They can be likened in this respect to an animal that hibernates for the winter after spending the summer storing food within itself to carry it safely through the winter sleep. A resting plant is in a similar state, having spent the summer making up bulbs that contain sufficient moisture to carry it through the winter. The roots stop growing and taking in moisture. Many orchids will spend the winter months in this dormant state, their bulbs remaining hard and plump without the assistance of extra water.

It does not follow, however, that all orchids rest, and this can be clearly seen by observing the plants themselves. By autumn some orchids have completed their pseudo-bulbs, but the bulbless types do not rest, and must therefore be kept moist throughout the winter. The bulbous types may, at this time, shed some or all of their foliage (the first indication of their coming dormant period). Provided there are no signs of new growth, the plant is, to all appearances, commencing its rest. From this time on the plants need no water and can stand in the full light. It may be an advantage to move them from the staging to a shelf close to the glass, where they can enjoy maximum light.

Those orchids that do not rest for the winter usually slow down their growth, but otherwise they require the same attention as during the summer. Continue watering, to keep the plants evenly moist — though at longer intervals as they will take longer to dry out. These continuous-growing plants lose a percentage of their foliage at the beginning of winter, but at the same time new growth will appear from the base of the latest completed bulb, and this will continue to grow throughout the winter. To withhold water from a growing plant will result in a much smaller bulb being made by the end of the season. The bulbs should progress in size until they reach maturity. If they become smaller year by year, it is clear that the conditions provided do not suit them.

 

The resting plants should retain plump bulbs while they are in their dormant state. If any undue shrivelling takes place, water the plants thoroughly once and the bulbs will plump up again in a very short time. At any time after late winter (January), watch the resting orchids for signs of new growth. Once this happens, it is clear the plants have woken up and are on the move again. When the new growth is about 5-10cm (2-4 in) high (smaller on dwarf plants) the new roots will appear. Begin watering again at this stage; the new roots just being made will need all the moisture they can get, but be careful to avoid over-watering.

Flowering cycles

It has been seen that orchids flower at different times of the year, and therefore at different periods of their growing cycle. Some orchids bloom during their resting period while others produce spikes when in full growth. Therefore the flowering-time need not necessarily be taken into consideration when deciding whether or not to water. A plant that blooms during its resting period has retained sufficient energy in its bulbs to support the growth and flowering of the spike without the assistance of extra water. Plants that flower during their growing season usually do so from the new growth when very young, and only after flowering do the new roots appear, so again the older bulbs support the new growth and flower spike. Watering should be quite straightforward if you watch your plants instead of the calendar, and make sure to water growing plants only.

Orchids should bloom annually quite naturally after a good growing season. If they fail to do so, the culture is at fault. A well-grown, contented plant will bloom without any further assistance from the grower. This, basically, is the art of orchid culture, and every grower strives to bloom every plant in their collection at least once a year.

Potting and repotting

When it comes to potting orchids, bear in mind that the vast majority of those grown in greenhouses are epiphytic by nature. A good basic compost for all orchids is fine bark chippings, either used by itself or mixed with a small percentage of sphagnum peat or sphagnum moss. This provides a good, open, well-drained compost that does not deteriorate quickly and through which the orchids can push their roots with ease. Either plastic or clay pots can be used, but you will find that with such an open compost clay pots will dry the plants out very much quicker. Most growers today use plastic pots.

 

An orchid plant is in need of repotting when the leading bulb or growth has reached the rim of the pot and there is no room for any further bulbs to be made within it. It also requires repotting if the roots have become so numerous that they have pushed the plant up above the rim.

In any case, you should repot orchids every year, choosing a pot large enough to allow for a further season’s growth. Remove the plant from its old pot, shake the old compost from the roots or clean it out from between the thick rootball. Trim the roots if they are very long, and remove any dead ones.

Orchids are propagated by removing the oldest bulbs from the back portion of the plants. Provided these are firm and not too old, they can be potted up on their own, and will most likely begin new growth within six weeks or so. Any number of leafless back bulbs can be removed from a plant, provided it is left with at least three strong bulbs to maintain its flowering size. The slightly-reduced plant will probably fit back into its original pot. Place the last remaining bulb towards the rim of the pot and leave maximum room for growth to the front of the plant.

Good drainage is important for all orchids, so place a layer of broken crockery at the bottom of the pot. Put the plant into its new position, keeping the base of the new growth level with the pot rim. Fill in the compost all round and push down with the fingertips until the surface is slightly below the rim of the pot. This will allow for future watering and prevent the compost from being washed over the edge.

Indoor culture

The cultivation of orchids in the home is becoming increasingly popular. In spite of certain difficulties over conditions, you can encourage orchids to thrive indoors if you understand what requirements are necessary.

Standing a plant over a hot radiator or in the centre of an ill-lit room gives it no incentive to grow and only spells disaster. Much more thought must be given to growing orchids indoors, and you will only be successful if you can maintain the all-important growing environment that they need. If you have a large, south-facing bay window available where house plants thrive, there is a good chance that some orchids will do well there also. The best type of orchids to select are those that can do with less humidity and that generally rest for part of the year. One or two examples are Odontoglossum grande, with large, striking flowers of rich yellow and chestnut; Laelia gouldiana, with large, brightly-coloured flowers of mauve; Dendrobium nobile, with clusters of pink and white flowers; Coelogyne ochracea, with small sprays of fragrant white and yellow flowers; and Paphiopedilum insigne, with long-lasting bronze and green flowers.

By far the best and most certain way of growing orchids in the home is to put them in a mini indoor greenhouse or orchid case. These are now generally available, including ones that have been designed specially for orchids. They provide heat, light and ventilation, giving a permanently controlled microclimate in which the orchids can thrive, with minimal cost, throughout the year. Ferns and foliage plants can be added to create a good-looking showcase for permanent display.

Propagation by meristem culture

Many seedlings can be grown from a single pod taken from a hybrid. When these finally reach flowering size (a process that takes approximately four years), no two plants ever produce identical blooms, each one being an individual.

Only the best quality plants produced are taken on for meristem culture. This is a method of mass propagation of a single clone or plant. It is a highly-organized technique (mainly practised by commercial growers with cymbidiums) that involves taking the youngest growth from the plant and removing from its centre the nucleus of growing cells that is the meristem tip. No larger than a pinhead, this small embryo is cultured in the same way as the seed; from this minute piece of tissue any number of identical ‘carbon copies’ can be successfully produced. This process takes a further three to four years before the plants will be of flowering size. These orchids will always be referred to as `meristems’.

The grower now has two choices. He may prefer to purchase unflowered seedlings of unknown expectancy, with the excitement of flowering them for the first time and hoping for one outstanding variety, or he can obtain proven meristem-cultured plants, knowing exactly what he is buying. This latter choice is preferable when buying for the cut flower market since you can obtain exactly what the florists require.

The orchid seed pod is produced by crossing two selected flowers. It takes up to nine months to ripen on the plant. The pod, heavily laden with literally millions of incredibly small seeds, is ready for sowing when splits begin to appear along the edges. The seed is sown in sterile flasks on a special growing medium (obtainable from a specialist nursery) that includes various salts and sugars for the nourishment of the seed. The young plants thrive in these sterile conditions and after 12 months they are strong enough to be taken from the flasks and potted up. From this stage on they are repotted at regular intervals until they reach flowering size.

12. July 2011 by admin
Categories: Greenhouse Gardening, Orchids, Orchids | Tags: , | Comments Off on Orchid Care and Orchid Cultivation

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