Repotting is something that should be done when you first get a plant, and about once a year or two as the medium decays and you need to replace it. The types of media that you choose should directly reflect your care habits. You can change the medium, but it’s harder to change your habits. Therefore, if you are a doting, heavier waterer, or are in a greenhouse, then you should choose a coarser medium to plant in. If you are more forgetful when it comes to watering, or you are growing indoors, then you should choose a medium that retains more water.
General Principles of Repotting
In nature, the universe is infinite! When a plant runs out of nutrients, it expands its roots and searches elsewhere. In a pot or in your growing space, the universe is not infinite, and therefore, medium and nutrients have to be replaced. Remember, YOU are the master of your plants’ universe – it’s up to you to ensure that the plants are potted or mounted appropriately, and that, through the medium, they are getting enough nutrients, and that the medium appropriately wicks the right amount of water to the plant.
Repotting should occur yearly or every other year, as needed by the plant, OR when you first receive the plant. When you bring home a plant, if it’s potted, it should be repotted within two weeks of bringing the plant back into your conditions. If the plant is in bloom, wait until the plant comes out of bloom. If absolutely necessary, one can repot a plant in spike or bloom, but risks losing the flowers prematurely.
Some of the more traditional orchid growers may claim that repotting an orchid at the wrong time will kill it, but unless you damage more than 50% of the roots, that’s highly unlikely. In reality, if a plant needs to be repotted, and you repot it, the plant will not be stressed, but rather, will be grateful and should reward you with a flush of new growth.
If you want to repot with no risk of growth set-back, you should repot just as new roots are beginning to form. If you do not damage the new roots, the new roots will establish themselves in the new medium very rapidly.
Onwards to choosing a pot!
Unless you are super experienced with plants, do not ever grow any orchid without drainage. Always choose a pot with drainage holes. Additionally, many indoor growers choose to do the “slip pot” method of potting, where the plant is planted in a cheaper plastic pot for its own needs, but that pot is slipped inside of a nicer ceramic pot for aesthetics. Additionally, the slip pot method can help with retaining moisture around the roots. Some indoor growers even take mounted orchids and sit them up in a pot, lightly filling the pot with some sphagnum in a way to “pot the mount.” This method is useful for not dismounting an orchid, but growing it in lower humidity environments.
- Terracotta – this material dries the fastest. Terracotta is porous and allows water to escape evenly. This is a great choice for super large plants, or plants that like to dry quickly between waterings. The downside is that terracotta is heavy, so if you are using it for a bigger plant, be sure you’re probably not going to be moving it often. Additionally, terracotta pots are a near death-sentence indoors for the wet-dependent orchids such as Miltoniopsis, Cochleanthes, and the like.
- Glazed Ceramic – Dries slower than terracotta, and is great if you like more stylish pots. However, the downside to these is that many do not have drainage holes, and of the ones that do, they may not work with a nice saucer beneath to catch what does flow through. It’s best to stage an orchid in a clear plastic pot inside a decorative ceramic so that the roots can get light, and you can hide the plastic pot underneath.
- Plastic – Dries the slowest, and is recommended for most orchids, especially indoors. The downside is that if you have a dark home, plastic might keep the medium too wet, leading to fungus gnats, root rot, and such. These are best used on plants that get a lot of light, heat or need to stay moist to help them retain water for a tad longer. Most indoor plants should be planted in clear plastic pots to allow photosynthesis of the roots. Even most outdoor/greenhouse orchids should be planted in plastic pots!
- Metal – You should not use metal pots for plants ever. No exceptions. They often leak, and are often made of cheap metals that corrode and poison the plants over time. Just because they look good in a magazine, does not mean that you should use them.
Choosing the medium
Plant care is a big balancing act. If you change one variable, you must change others to compensate. The medium that you plant your plants in is one of the biggest areas of variability, based on your conditions. If you have wetter conditions or simply water frequently, then you will want a coarser medium for your plants. If you are stingy with water or forgetful or simply growing indoors, you will want a medium that retains more water. Smaller plants generally need finer medium, and larger plants generally need coarser medium.
- Sphagnum moss – Made from dried moss, if you end up getting live sphagnum, it actually produces acid on its own, so will naturally acidify the medium (again, only if alive). Live sphagnum is really only recommended for growing carnivorous plants or orchids that are found in bogs, which are naturally acidic anyway. Dried sphagnum does not change the pH. Nearly all orchid mounts should be padded with sphagnum, and all indoor orchids should have some sphagnum in their medium. Beware because sphagnum retains moisture when wet… but when it dries out, it actually repels water. So, just “premoisten” the sphagnum on the top of your orchids, and then water normally about 5 min later. It should absorb much better.
- Fir bark/Orchid Bark Mixes – are usually cedar/pine or fir bark mixed with charcoal, perlite, and sphagnum in varying degrees of coarseness and ratios. Most of your orchids that like to go fully dry between waterings can be planted in this. If growing indoors, add more sphagnum or tree fern fiber. It never hurts to add charcoal if you have hard water to help pull out the excess salts. For orchids that like it drier, or for growers that water more, use the coarser grade. For orchids that like it wetter or for orchids whose conditions you do not know, use finer grades or do not use a bark mix.
- Tree Fern Fiber – is made up of shredded tree fern bark, and is historically, the best medium to grow most orchids in. The issue with tree fern bark is that historically, it was unsustainably harvested, and tree ferns take a long time to grow back, which made it expensive. Now, in New Zealand, there are sustainable ways of harvesting the fiber, which has brought this mix back into the fray. This is a great addition to other mixes, or used as-is for potting orchids.
- Perlite – is inert volcanic glass that’s added to other media to both provide a source of silica as well as to help the media retain less water.
- Horticultural Charcoal – is mostly elemental carbon, and acts as a fertilizer/salt sink. This is very different material than the sort of charcoal used to make fire briquettes! If you have too many salts in your water, adding extra charcoal helps, but once the charcoal is at capacity (as denoted by a white chalky film), then you need to replace it. Charcoal is added to bark mix to help it last longer and not rot as fast.
How do I know when to divide or just repot?
If you are looking to divide an orchid, ensure that each division that you will make will have at least three or more pseudobulbs not counting any new growth. That means, at minimum, a plant has to have six pseudobulbs before you attempt to divide it. Fewer pseudobulbs per plant will result in setback of over two years, or non-growth, as the plant will be too small.
