Repotting Orchids – Essential Orchid Information
Really experienced orchid growers like to prepare their own growing medium according to their own recipe. If you have only a few plants on your windowsill, however, you are better off purchasing a commercially produced standard orchid. Ask a reputable orchid grower what medium to use for individual species of orchids.
When purchasing or ordering orchids, obtain one or two bags of orchid-growing medium at the same time, so that you have it handy.
Whether you buy ready-made compost or mix your own, every orchid-growing medium should have the following characteristics:
- It should be air- and water-permeable and retain warmth.
- It should be lightweight and loose but still hold the plant securely.
- It should absorb water easily but also drain quickly.
- Nutrients should not break down too quickly so that there is a flood of nutrients all at the same time, thereby raising the salts content in the medium.
- It should show a slightly acid pH value.
Do not use ordinary, undiluted flower compost for orchids! It is totally unsuitable.
The constituents of orchid-growing mediums
Orchids may be grown in organic, mineral or synthetic mediums or in a mixture of all three.
The classic orchid-growing mediums containroots, tree (like Xaxim and Mexifern) and Sphagnum moss. All three can still be obtained from orchid suppliers but no one knows for how much longer this will be possible as regulations designed for the protection of species and various nature protection agreements prohibit any future plundering of these natural resources.
Modern orchid-growing mediums consist of:
- peat products, such as moss peat, sedge peat, peat compost
- types of tree bark, like Meranti, redwood, cork oak, pine bark and cork chips
- polystyrene products like orchid chips or polystyrene flakes
- mineral substances, like Hortag (for orchids in hydroculture), pumice gravel, glimmer, shell lime, dolomite lime, lava and perlite.
This group also includes chippings of a mineral-rich volcanic stone whose weight will provide anchorage even for tall-. Although the pH value of this substance (at 7.5) is rather high, orchids appear to thrive on it. Particularly good results have been obtained with grande.
What these substances do
Mineral constituents provide minerals and trace elements. Synthetic substances prevent rapid clogging, waterlogging or rapid cooling down of the planting medium. They also promote better ventilation.
Natural or organic substances support root formation and provide nutrients. Charcoal chunks prevent infections and decay. In the case of, a little standard compost is often added as a source of nutrients or a little loam may be added to give the medium “hold”. Warning: The pine needles or beech leaves that are often used in growing mediums for orchids can be carriers of disease!
Good growing mediums for orchids
Add a specialist orchid fertilizer to your own growing medium mixtures. Make sure that you follow the dosage instructions to the letter. Specialist fertilizer contains all the important trace elements for a good start in the new vegetation cycle. Do not use ordinary fertilizers.
For epiphytes in pots:
- 1 part cork chips
- 1 part pine bark
- 1 part polystyrene flakes
- 1/2 part peat
- 1/2 part charcoal
- 2 g carbonic acid powder per litre growing medium
- 5 parts fine pine bark 2 parts peat
- 2 parts pumice gravel
- 1 part charcoal
- 2 g carbonic acid powder per litre growing medium
For terrestrial orchids:
- 2 parts pine bark
- 1 part peat
- 1 part fine compost
- a little loam
Never throw away packaging material made of polystyrene. If it is chopped up small, this can be reused by adding it to compost or as a layer for drainage purposes.
Orchids in polystyrene
The most modern types of compost are completely synthetic. Orchid chips are made from a polystyrene mixture with a very rough surface. These chips have proved very successful in practical trials with all orchids which can be grown in this medium alone.
If you are growing your plants in orchid chips, you should fertilize them all year round.
Whether you grow your orchids in pots or wooden containers will depend largely on your own taste and on the position of the plants. A flowerpot is still the best type of container for a windowsill. If you have a plant window with a climate specially adapted to plants, you may place your plants in decorative hanging containers or tie them to pieces of bark, branches or roots.
Nowadays most orchids are offered for sale in plastic or clay pots.
Clay pots are air and water-permeable and are more stable because of their weight, but they dry out a lot faster than plastic pots and may allow salts to accumulate which, in turn, can burn the roots of orchids under certain conditions. In addition, these pots may look unsightly after some time, due to deposits of lime on their sides. Plastic pots do not allow the compost to dry out so quickly and will always remain clean but they do tip over rather easily. The best plastic pots have thick walls in light colours, which do not break so easily and will not heat up quite so much in strong sunlight.
Containers or large plant tubs made of terracotta, wood, ceramic or plastic make ideal plant containers for large, spreading orchids like Cymbidia.
These are very suitable for orchids with flowers that hang down. Lattice baskets have the advantage of allowing air to reach the compost and roots all round. As they may look dry from the outside but still be moist on the inside, you will need to be careful about watering them.
Pieces of bark, branches and roots
The orchid and its compost material are tied to this growing base. The most suitable materials are cork or the bark of pine or oak.
My tip: Special expandable planting boxes can be used for smaller, sympodially growing orchids. These can be expanded when required, which avoids the necessity to repot the plant.
The right way to repot
First fill a third of the new pot with coarse polystyrene flakes. Add a handful of fresh compost. Stand the plant on top. Surround the rootstock with additional compost. Press down. Leave an edge of 1-2 cm (1/2-3/4 in) for watering. Sympodial orchids likeshould be placed in such a way that the new shoot is pointing towards the centre of the pot. Monopodials should be set right in the centre.
Any kind of repotting is stressful to orchids. Repotting will, however, become necessary in the following circumstances:
- If the compost has become hard and dense and is no longer air or water-permeable.
- If the plant is too large for the pot and is constantly in danger of tipping over.
- If a plant’s new growth is becoming too much for the old pot and is beginning to grow over the edge.
- If the plant is sick.
How often should an orchid plant be repotted?
The frequency of repotting orchid plants will depend a great deal on the shape of growth of the orchid and also on the type of compost. Plants may grow happily for years in completely synthetic polystyrene. Chips for example. Natural compost material, which will decompose and break down over a period of time, will have to be renewed more often.
When to repot orchids
Always repot orchids at the beginning of a new growth period. You will recognize that the time is right by the appearance of fresh, light green shoots and when the orchid begins to form new roots. In many species, the ideal time lies between late winter and late spring. Some orchid growers like to repot orchids after flowering is over. Some consider late summer – particularly for– the most favourable time.
Do not wait too long before replanting an orchid in a new pot. By the time the plant has finger-length new shoots it will find the change harder to cope with.
Preparing the new pot
The new container should be absolutely clean and not too large because a very thick layer of compost in a pot that is too large tends to prevent oxygen from reaching the roots. Remember to soak clay pots in water for 24 hours before repotting.
Ensure that an adequate drainage layer is placed at the bottom of a new pot. The layer should be 1-3 cm (up to 1-1/4in) thick and consist of polystyrene flakes, pumice gravel, Hortag or clay pot shards.
How to repot orchid plants
The main requirements are gentle hands and lots of patience. Above all things, an orchid will not take kindly to damaged roots.
Step 1: Water the plant well the day before repotting so that its roots are smooth and flexible rather than dry and brittle.
Step 2: Carefully loosen the rootstock in the old pot. If it is stuck, cut a plastic pot open along the side or break a clay pot with a hammer. Orchids in wooden containers should have their roots carefully loosened before removing them.
Step 3: Now shake the rootstock gently without allowing the plant to fall apart. Parts of the roots that look diseased, dried up or shrunken should be cut off with a very sharp knife or with scissors. Plants that are too large or very old can be divided when repotting and thereby rejuvenated.
To avoid the risk of infection, first disinfect your knife or scissors with alcohol and then treat the cut surface of the plant with charcoal powder.
Step 4: Place a thin layer of new compost on top of the drainage layer in the prepared pot. Place the rootstock on top of this and surround it with the rest of the compost. While doing this, occasionally tap the pot against the edge of the table to help the compost particles to shake down into all the cracks and spaces. This gets rid of hollow spaces between the roots and will help the roots to make thorough contact with the compost.
Monopodial orchids (likeor Phalaenopsis) should be placed in the centre of the pot.
Sympodial orchids (like Cattleya,or ) can be potted in such a way that the oldest bulb is close to the edge of the pot while the new shoot is in the centre. This is the only way that the plant can spread unhindered. Aerial roots which have developed facing towards the compost can be packed with compost as this will help the plant to gain a firmer hold. They can also be allowed to hang over the edge of the pot.
Step 5: Allow a space of 1-2 cm (up to ¾ in) around the plant for watering purposes.
Very tall or heavy plants with relatively weak roots may sometimes have a tendency to tip over after repotting in loose, soft compost. The best plan is to drive a stick made of wood, bamboo or plastic deep into the compost and tie the plant to it to give it support as it grows.
After repotting orchid plants
- Place the freshly repotted orchid plant in a bright, but on no account sunny, position.
- New root formation will be encouraged if a heating mat is placed underneath the pots.
- In contrast to most indoor plants, orchids should not be given water immediately after repotting. This is because the damaged parts of roots are better able to heal in compost that is merely moist and fresh from the bag. Also, a minimum of moisture encourages the roots to grow in order to seek it.
- After eight to 14 days, the orchid plant may be watered normally and according to its requirements.
- Orchid plants tied to a base should also be placed in a bright but not too sunny position. During the first two weeks, spray but do not water.
Tying up a tall orchid plant
Tall-growing orchids will require support after repotting and can be tied to a stick made of bamboo or wood. Secure the shoots with loose, figure-of-eight-shaped loops of twine, soft plant wire or anchoring clips.
The right way to secure orchids to a base
Place plant compost in front of and behind the roots. Tie the plant to the tree fern block or piece of bark in such a way that no water is able to run into the heart of the plant. Tie up the plant with strips of ladies’ tights.
Sympodially growing orchids will have to be repotted approximately every two to three years on average, for example: Cattleya,, Laelia, Odontoglossum, . Monopodial orchids are, as a rule, repotted every three to four years, for example: . Paphiopedilum and Phalaenopsis should, however, be repotted every two to three years.