Growing orchids in water, also known as water culture is an advanced technique in orchid care and not recommended for beginners. It is best to have some experience with growing orchids before trying this technique. There are various methods of doing this and are sometimes referred to as full water culture, semi water culture, and semi-hydroponic or self watering. Each of these methods have a slightly different technique to them. The best way to describe this is that with full water culture and semi-hydroponic water culture, the roots always have a reservoir of water that they are either always in contact with or have access to, such as by wicking action in LECA. In semi water culture, the roots are soaked for a period of time in water and then allowed to dry out for a period of time.
Some orchids will do very well in water culture and some orchids do not take to water culture at all. Sometimes it may have to do with the species of orchid, the climate environment that the orchid is growing in, the orchid may be unhealthy to begin with, or sometimes it may have to do with how you transition the orchid to water culture from the growing medium that it has been growing in.
If you are a person with a busy schedule or who travels a lot and you do not have a lot of time to care for your orchids, water culture may be a good solution for you. Some orchids will do very well with this type of growing environment, some will not. There is a learning curve to growing in water culture, so start with one plant first as you learn this process. For our purposes on this page we are discussing full water culture.
If it is your first attempt at transitioning to growing orchids in water culture, there are a few key steps to take. The first step when you remove your orchid from its growing medium is to clean the roots by removing as much of the growing medium as possible. Although it is not necessary for the roots to be completely cleaned, do your best to remove as much as you can initially, and continue to remove any remaining medium over time until you just have bare roots. The next step is to prune any dried up or dead roots that you find. Allow the roots to heal for a day or two before putting them into water culture. If you do this too soon, you may inadvertently cause harm to your orchid and it may not survive the transition. Orchids are epiphytes and can actually survive quite well for some time without water, so don't worry about leaving the orchid out of a medium for a day or two. Once the roots have had a day or two to heal, you can now transition your orchid into a water culture.
When transferring an orchid to a water culture container for the first time, it is a good idea to start with a clear glass container or vase so that you can keep a close eye on the orchid roots. Choose a container that will gently support your orchid without putting stress on any area of your plants. A container should be a diameter that the base leaves can gently support the weight of the orchid without putting undue stress on the plant. The container depth should be deep enough to allow the roots to stretch out without being crowded or curling around the bottom of the container.
When first transitioning to growing orchids in water, start slowly with the tips of the roots being in contact with a small amount of water. For Phalaenopsis, start by introducing the roots to being submerged in approximately one inch of water. This is a general measurement to start with, and depending on your plants water needs, this may be a good level to maintain, or you may find that you can increase that slightly, if the roots are drying out too quickly. The majority of the roots should be exposed to air. Mini Phalaenopsis may take higher levels of water with 1/3 to 1/2 of the roots being submerged in water. Follow the guidelines for Phalaenopsis, start with slowly introducing the roots to being submerged, but it may be possible to introduce higher water levels for mini Phalaenopsis every few days. It is also recommended to transition orchids to water culture during warmer months when their water needs or higher and temperatures are warmer. Monitor your plant closely for the first few days to the first few weeks and observe how it is doing. If the leaves start to droop and look thirsty, give the air exposed roots some light misting daily to twice daily until the plant takes to the transition. Observe the roots and look for darkening or rotting. Some orchids will love the new growing environment and start to thrive, other orchids may not, this is why it is best to try this technique when you have gained some experience with growing orchids and can detect quickly whether your orchid loves or hates it.
When growing orchids in water culture, it is a good practice to change the water weekly. When replacing the water, use a non urea based fertilizer recommended for orchids. Remember the adage, water weakly, weekly. So when replacing the water use a 1/4 strength solution of water/fertilizer mix. Most fertilizer's will likely recommend a monthly feeding, so divide the recommended dosage by 4 for weekly feeding. For example if the manufacturer recommends 1 tablespoon of fertilizer per gallon of water per monthly feeding, divide that by 4. That would work out to approximately 3/4 teaspoon per gallon of water. There are many online calculators to convert measurements whether you use the imperial system or the metric system, depending on where you live.
Orchids seem to love kelp. In some cases, if you have been having a difficult time with getting an orchid to rebloom, fertilizing occasionally with Kelp may induce the production of a flower spike and bloom. If you are growing orchids in water and have developed the good habit of changing your water/fertilizer solution on a weekly basis, replacing the fertilizer solution to a Kelp/water solution once a month will have beneficial results. If you would like to learn more about growing orchids in water culture, Danielle's Orchid Ranch station on Youtube has an extensive set of tutorials that are very helpful and a great resource on this topic.