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Also known as the boat orchid, Cymbidium (sim-BID-ee-um) hybrids descend from species originating mainly in the Himalayas, the mountainous regions of India and China. They can also be found throughout the Far East: through Japan, Philippines and Australia.

Cymbidium orchids are large evergreen plants; they have “strappey”, grass-like leaves shooting from pseudo-bulbs at the base of the plant. They are clump-forming and have fleshy roots.

Cymbidiums are usually grown in conservatories or cool greenhouses. Different varieties flower between September and April. There are two main types of Cymbidium, standard and miniature. Standard Cymbidium – differentiated from miniature cymbidium by the size of the pseudo-bulbs and flowers – prefer cooler conditions to miniatures.

Flower spikes are produced in autumn or winter from the newest pseudo-bulbs. Initially they look like leaf growths but the flower spikes tend to be rounder at the tip and more fingerlike than leaf growths. A flower spike may carry 1 to 30 blooms depending on the variety

Temperature: When in flower, Cymbidium like cool house temperatures of between 15-20°C. The warmer they are kept, the shorter the flowers will last.

In summer, when the plants are out of flower, they need hot bright days (25-29°C) and cool nights (10-15°C) to initiate flower spikes. This can be achieved by setting the pots outdoors during summer under dappled shade away from midday sun, (to avoid leaf burn). Feed and water regularly during this period. The plants should spike up when the temperatures fall in the autumn to below 10oC. Bring the plant indoors before the first frost. Once the plants have formed their flower spikes and the buds are well developed they can tolerate slightly warmer temperatures of 15–20°C.

Note: To help prevent flower and bud drop, keep plants away from drafts, radiators and other heat sources.

Light: Cymbidium like plenty of light in the summer, but not full sun. A combination of long hot days and cool nights during July and August will initiate the flower spikes. This is also a good time to feed the plants with a high potassium feed or “bloom booster”. Plants need less light when in bud and/or bloom during the winter.

Note: Direct sunlight can burn the bloom and leaves.

Water: At least once a week throughout the year. Water from the top and allow any excess to drain away. If the plant is large, it may be easier to submerge it in a bucket of water before allowing it to drain. Clean rainwater is preferred by the plant but you can use tap water if necessary. Do not allow the compost to become waterlogged. Water weekly as a general rule but if the plants are kept in a warm environment they will need to be watered more frequently.

Note: Never stand the plant in water for more than 10 minutes.

Feed: As orchids go, Cymbidium are quite hungry and require regular feeding to produce good flowers. Feed once a week during spring, summer and autumn using a balanced orchid fertilizer, such as Ivens Orchids’ Orchid Feed, and once every two weeks during the winter. A high potassium feed or “bloom booster” can be applied from July to September instead of the balanced feed.

Air Humidity: Good ventilation (not drafts) and moist air are essential. The humidity can be raised by placing the plant on a tray of moist gravel or pebbles. 50% humidity is ideal.

After Flowering: Cymbidiums will not flower if kept too warm or with insufficient light. They flower once a year and usually for at least six weeks. Once flowering is over, cut off old flower stems near to the base. To initiate the next flower growth they must have cool nights throughout the spring and summer months. Stand your plant outside towards the end of May until the middle of September. Stand the plant on a slightly raised base to avoid slugs getting into the pot. Early morning sun is ideal but provide some shade against strong sunlight. Remember to continue feeding the plants during this period.

Repotting: Repotting and dividing are best done in spring after flowering but only if your plant has outgrown its pot – Cymbidium like to be very restricted in their pots. A specimen plant can be produced by potting up regularly. A larger plant usually produces more spikes but sometimes a plant that has been mistreated or just becomes too old may benefit from dividing as this may regenerate it. Use orchid compost, such as Ivens Orchids Cymbidium Compost, that is moderately free draining whilst retaining some moisture. Repotting and dividing classes are available from Ivens Orchids.

Basic Repotting Technique: Cymbidium are tough plants and repotting them, and especially dividing them, can be a very strenuous job; you will need a strong knife and sharp secateurs.

Tap plant out of its old pot or if very pot-bound you may need to cut the pot away; the plant will be easier to remove from the pot if it is dry. Inspect the condition of the root-ball: In a healthy plant, the pot should be almost completely full of firm creamy roots with pale green growing tips. Generally, a cymbidium will grow in one direction so it will have a “back”, (where the oldest growths are,) and a “front”, (where the youngest growths will shoot). If you can see a directional trend in the plant to be potted bear this in mind when positioning the plant within the pot and allow space for the new growths to develop without making the plant look lop sided. Use a pot big enough for you to get two fingers around the root-ball between the roots and the inside of the pot. Holding the plant upright, feed compost around the root-ball; there probably isn’t a lot of room between the roots and the sides of the new pot but pack in as much compost as you can, making sure it goes right to the bottom of the pot where you want the new roots to grow.

Cymbidium can be potted firmly. Always dampen down the compost before potting and water as normal after repotting.

Dividing: A plant that needs to be divided will be large and old with many pseudo-bulbs. Some may be so old they no longer carry leaves; these are known as back-bulbs and are useful to the plant as storage organs for water and nutrients. The plant may also have bulbs that are black and soft; these are no use to the plant and must be removed. When dividing, look at the plant to see if it shows natural breaks between the growths where it could be divided. The intention is to divide the plant into two or three good sized plants that have at least 3 or 4 pseudo-bulbs. Tap the plant out of its pot as described in ‘Repotting’ above, then cut through the plant using a strong sharp knife, trying to avoid cutting through a bulb or new growth. Once you have your divisions, shake off any loose compost teasing out any dead or loose bits and remove any old, brown, soggy or damaged roots. Also remove any old black or soft bulbs, cutting them away if necessary. The live roots that are left can now be trimmed to about 10 to 15cm; this will help prevent damaging them during re-potting and allow the plant to regenerate. Do not worry that it looks to be a large amount of root to remove; a healthy plant will very soon develop new roots and the plant will benefit by repotting in this way. Using a pot big enough for the next year or twos growth, support the plant with the oldest pseudo-bulbs, (the “back”) at the edge of the pot and the “front” of the plant toward the centre of the pot. Cover the base of the pot with a small amount of compost then feed fresh orchid compost around the root-ball. Always dampen down the compost well before potting. Firm the compost with your fingers as you go.

The plant should not be watered for 2 weeks after dividing; thereafter the leaves may be lightly misted and watered sparingly over a period of about 8 weeks. This allows the new roots to develop and search for moisture within the compost stimulating good root growth; over watering would cause the plant to rot. Regular watering and feeding can resume once the plant starts to feel secure in the pot and new top growth can be seen.

Although dividing may sound drastic, provided it is done early in the growth season, (ideally March or April,) the plant will have sufficient time to produce new roots and still flower in that season. This is one of the reasons why the plant should not be over potted: i.e. the bigger the pot, the more energy the plant needs to make roots and the less energy it has to flower.

Handy Tip: A leafless back bulb can also be removed and propagated by potting up in its own, very small pot.

Pests: Prevention is always better than cure so look for good healthy plants to start with and keep them that way with a clean environment for your plants. Throw away old, weak or infested houseplants and maintain good housekeeping in the greenhouse. Most often seen pests are scale insect, aphids, red spider mite and slugs. All of these will weaken the plant if left unchecked. If found early enough, the scale and aphids may be cleaned off with soapy water, otherwise, treat with a specific systemic insecticide.

Buying Tips: Always buy good quality orchids from a reputable supplier and look for clean healthy plants. If buying plants in flower, check the flowers are not damaged and that the pollen caps are still on the flower, (if these get knocked off by poor handling or contaminated by poor storage or transport conditions, the flowers will very quickly discolor or “go over”. Unless you have ideal transportation and growing conditions, buying a plant with immature buds may be a mistake as some plants can be sensitive to being moved during the early stages of flower development. Look for plants whose flower buds look quite plump and ready to open. Don’t be afraid to buy a plant whose flowers are nearly all out, especially during the cooler months. Providing they are not kept too warm, Cymbidiums stay in bloom for many weeks even once all the flowers have opened and give a marvelous display.

Handy Hints: Keep your plants clean and healthy by occasionally cleaning the leaves with a mixture of 1 tablespoon of olive oil and a few drops of washing up liquid mixed in about 300ml of warm water. Using a sponge cloth, wipe over the leaves with the mixture. As old leaves die they fall off leaving behind dry brown bases. These can be removed by stripping or pulling away from the pseudo-bulbs. This helps to make the plant look tidy and prevents bugs from hiding around the plant base.

by IVENS ORCHIDS www.ivensorchids.co.uk

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