When to Repot Orchids? A Detailed Guide to the Repotting Method

During the cultivation of orchids, there will always be some phenomena that hinder the growth of orchids: after several years in a pot, the plants multiply, the root system becomes too dense, nutrients run short, the potting medium compacts, and pests and diseases appear. All of these affect the growth of orchids. When the above situations occur, the only solution is to repot, divide the plants, and replace the potting medium. A good repotting can promote active vegetative growth, improve the plants' ability to resist disease and regain vigor, and raise the sprouting rate, bringing vigorous vitality to the orchids. If repotting is done poorly, it can also bring potential danger to the orchids. Especially for some diseased and weak seedlings, it will accelerate their death.

Therefore, repotting is an important measure in orchid care, and it is a skill that every orchid grower must experience and master. At the same time, it should be noted that orchids should not be repotted frequently. Because orchid roots live symbiotically with orchid fungi, absorbing nutrients through the orchid fungi, repotting and replacing the potting medium too often will affect the orchid's nutrient absorption and normal development. Each repotting and each replacement of the potting medium requires the orchid fungi to regenerate and adapt to the new environment, and the orchid plants will be in a suppressed state for a period of time, stopping growth. Especially old seedlings and weak seedlings may very likely be worn out to death. Therefore, what must be repotted must be repotted, and what does not need repotting should be left alone as much as possible.

Because potted orchids are limited by the pot, as the orchids grow year after year, the soil nutrients are exhausted. The root system becomes too dense and the plants too numerous, making it hard for them to grow lush again, and at the same time it is unsightly. In order to promote better growth and reproduction, it is necessary to repot and change the soil or divide the plants. Repotting can be done in the three seasons of spring, autumn, and winter within a year, as long as extreme heat and freezing are avoided.

[Under What Circumstances Do Orchids Need Repotting]

Generally speaking, orchids need to be repotted once every 2 to 3 years of growing in the pot, mainly due to the following reasons:

1. The orchids have become crowded. After 2 to 3 years of reproductive growth, there are more and more orchid plants in the pot, which not only looks crowded, but also causes the orchid's sprouting rate to decline, and small weak shoots tend to appear.

2. There are too many roots. Modern orchid growing mostly uses granular potting media. The orchid root system in the pot is well developed, and after 2 to 3 years of growth, the roots become tangled and intertwined. Not only is there no room for new roots to grow, but old roots and hollow roots remain in the pot, not only taking up space but also easily breeding pathogens.

3. The potting medium has become spent. After several years of cultivation, the nutrients in the potting medium are exhausted and the medium becomes acidic. Not only are the new shoots thin and short, but the whole pot of orchids appears in a weakened state.

4. Problems have arisen. During cultivation, the orchids in the pot develop various physiological diseases, and may even be infected by pathogens and viruses, with diseased seedlings collapsing. In order to save the remaining orchid plants, repotting and replacing the potting medium for replanting is unavoidable.

5. The flowers are to be sold. Among modern orchid growers, there are few who purely grow orchids for their own enjoyment; generally, buying, selling, or exchanging takes place. Once an orchid friend comes to obtain stock or a friend comes to exchange, the plants must be taken out of the pot, divided, and replanted.

[Preparation Work Before Repotting]

Once repotting is decided, the relevant preparation work should be done three days in advance, mainly in three areas:

1. Soak the potting medium. Modern orchid growing mostly uses a mix of several granular potting media, and these granular media all need to be soaked before use. For example, Xiantu (a type of fired clay granule) must be soaked for more than two days, and others such as Zhijinshi, Zhenjiang orchid soil, orchid fungus soil, and ceramsite also need to be soaked to varying degrees. Soaking the potting medium generally requires first sieving it, separating it into three grades of large, medium, and small granules, and then soaking it in a disinfectant solution to sterilize and kill pathogens in the medium. Disinfectants such as thiophanate-methyl, carbendazim, chlorothalonil, and potassium permanganate can be used.

2. Select and disinfect the pot. The choice of orchid pot size depends on the orchid variety and its growth condition. Usually, for one variety of orchid, at least two sizes of orchid pots, large and small, should be prepared, so that large plants go in large pots and small plants go in small pots; plants with many roots go in large pots and plants with few roots go in small pots. Newly fired orchid pots should be soaked in water for more than one day, then soaked in a diluted fungicide solution for more than two hours, and after taking them out, rinsed clean with clear water.

3. Withhold water from the orchid plants. Stop watering three days before repotting, and do not let the potting soil remain moist. When the potting soil is dry, it is beneficial to the smooth progress of repotting: first, it is easier to remove the plant from the pot and the root ball crumbles easily, making cleanup convenient; second, with less water in the orchid roots, they are less likely to break, making it convenient to arrange the roots and divide the plants, and the operation goes much more smoothly.

[Steps for Repotting Orchids]

1. Remove the plant from the pot

Tip the orchid pot over, rotate the pot with your left hand, and pat the pot wall with your right hand so that the potting medium in the pot loosens. The medium will naturally keep coming out of the pot, and the orchid plant can then be taken out. In a few pots where the orchids are more vigorous, have numerous roots, and grow tightly against the pot wall, even after repeated patting, it is still not easy to loosen them. Be patient and keep patting, and you can also use a wooden stick to push up from the drainage hole at the bottom; generally they can be taken out smoothly. If there is truly no other way, the pot has to be broken to get the plant out.

2. Rinse the orchid plant

After the orchid is taken out, if the root area is very clean, it does not need rinsing; carefully remove the potting medium. If the soil is relatively wet and hard to pick off (such as mountain mud, which is harder to remove), it can be placed under a tap to rinse clean.

3. Hang upside down to dry

After rinsing, the orchid roots are full of water and easily broken, so it is not suitable to arrange the roots, and even less suitable to divide the plants. To make the operation easier, after washing, the plant should be placed in a cool, ventilated spot to dry a little, preferably hung upside down to avoid water accumulating in the leaf crowns. Never place it in the sun to bake. Wait until the roots become soft and white before arranging the roots, trimming, and dividing the plants, otherwise the roots will break or fall off.

4. Careful trimming

The orchid plants that have been left to dry should be trimmed. Use sterilized scissors to cut off rotten roots, hollow roots, shriveled roots, and diseased roots. If there are few orchid roots, the root core can be kept to support the orchid plant. At the same time, trim off residual leaves, rotten basal leaves, diseased leaves, and hollow, shriveled old pseudobulbs.

5. Scientific division of plants

If the orchid clump is relatively large and needs to be divided, divide it appropriately. The division should be done scientifically, starting from the goal of producing more sprouts and growing large plants. Use sterilized scissors or a scalpel to carry out the division.

6. Apply medicine and disinfect

The cuts from trimming and division should immediately be coated with medicinal powder; generally thiophanate-methyl, carbendazim, chlorothalonil, and the like are better for dressing wounds. Afterwards, disinfect the divided orchid plants; generally soak for about 15 minutes to eliminate pathogens and viruses remaining on the orchid plants. After soaking, take them out and hang them upside down, let them dry appropriately, until there is no water between the leaf crowns and the root system is soft, and then they can be planted.

7. Mix and blend the potting medium

Mix the disinfected and soaked potting medium in proportions. Generally speaking, the ratio of Xiantu, Zhijinshi, Zhenjiang soil, and orchid fungus soil is 4:3:2:1. If the old potting medium is disease-free and pathogen-free, it can also be sieved, divided into three grades of large, medium, and small, disinfected by sun exposure, then soaked in disinfectant solution for two days for sterilization, drained, and mixed into the new potting medium for use, but the proportion of old potting medium should preferably not exceed one third.

8. Match the plant to the pot

According to the condition of the plants, choose orchid pots of a suitable size. Generally speaking, large plants use large pots and small plants use small pots; many plants use a large pot and few plants use a small pot; many roots use a large pot and few roots use a small pot.

9. Place a drainage cover

First place a drainage cover at the bottom of the pot. Generally speaking, large pots use a large drainage cover and small pots use a small drainage cover. The drainage cover can be homemade or bought at the market.

10. Add a drainage layer

After the drainage cover is placed, put loose, soft, and not easily broken charcoal, Zhijinshi, or other potting medium about the size of a thumb around the drainage cover to ensure ventilation and air permeability at the bottom of the pot.