You have probably heard this many times: you need to repot your orchids regularly. There are a few exceptions that do not like their roots disturbed, Angraecum sesquipedale is a good example. It is especially important to repot Paphiopedilum orchids if you want to grow them successfully.
Why repot?
Most Paphs are sold in bark based potting mix. As the bark ages it breaks down and becomes soft and holds too much moisture. It can begin to go ‘sour’, turn anaerobic and smell bad. Roots require oxygen to stay healthy, so when the mix deteriorates the roots will deteriorate. Even if the mix contains inert material such as perlite the roots will suffer as it ages.
There is also the issue of mineral build up in older potting mix. We fertilize our plants to make them grow well, but most plant fertilizers are salt based. The salts build up in the media over time and inhibit root growth.
When do I repot?
We repot our Paphs year-round. The exceptions to this include the warmer growing multifloral species such as Paphiopedilum rothschildianum and Paphiopedilum philippinense. We try to limit repotting of this group to March through September as their growth slows down considerably during the cooler winter months. This also applies to the Parvisepalum group and other species that have a distinct cool rest period in nature.
The majority of the plants we sell are Maudiae type and complex hybrids. These are the ones that we repot whenever they need it. We even repot plants in bud or bloom if they are in bad potting mix. The plants are better off in fresh mix. When done carefully we have seen little impact to the blooms. It’s pretty amazing to see how often an unhappy Maudiae Paph ‘perks up’ when moved into fresh potting mix.
What type of mix should I use?
This depends on your growing conditions and watering habits. We prefer to use a very well drained mix with about 30% coarse perlite (roots need air!) Our base is Orchiata New Zealand pine bark. For pots up to 3.5” we use the Classic grade Orchiata and #3 perlite.
We sift the fine dust and particles out of the perlite before we use it in the mix. CAUTION: The dust from perlite is a health hazard. We recommend sifting it outdoors and that you wear appropriate personal protective equipment. You can use other inert material in your mix such as pomace or lava rock. We use perlite because it is light and provides plenty of air.
We also use about 25% charcoal in our mix. The same dust warning applies here…it can be messy to work with.
For larger plants in pots over 3.5” we use Power or Power Plus Orchiata with #4 perlite. This type of mix tends to last longer so we repot our large multiflorals every two years instead of annually.
There are online vendors who provide premixed media. Our local friends at https://flori-culture.com/ are a good option. If you can’t find the exact mix you like online you can always adjust it by adding a little more of your favorite components to make it better suit your needs.
Why so much drainage?
As I mentioned above, roots need air. A well-drained mix provides that. The down side is this type of mix may require more frequent watering, especially in a drier environment. We generally water once per week, but in the warmer months we do need to water some plants twice per week. This is especially true for smaller seedlings in 2” pots.
Some people like to add small amounts of moss to hold moisture in their potting mix. We do not, as we prefer to water more frequently if needed. Obviously if you are successful with what you grow in, don’t change it!
Also keep in mind that new bark mix often dries out much faster than established mix. You may have to water more frequently until the mix matures. This can be avoided by soaking the new bark in water for 24 hours before using it. This isn’t practical on our scale but certainly works for hobbyists.
In Summary
Repot (most of) your Paphs annually! They will reward you with robust growth and stronger flowers. Only repot species that experience a cool winter rest in the spring and summer, unless their mix has completely deteriorated and they are at risk of rotting. Otherwise, most of your plants can be repotted just about any time.