February 2024

My favorite well draining, moisture retraining, aerated, moderately fast drying potting mix for rooting and growing Hoyas. This mix is fantastic for both rooting cuttings and growing Hoya plants small and large. It is available at Carla’s Plants in 4 quart bags. 

Everybody who grows Hoyas has a favorite mix that works well for them. A lot seems to depend on where live, whether your Hoyas are inside the house or out, the average humidity and your watering routine. There is a bit of trial and error to finding the right mix for your Hoyas and it’s good to experiment to see which mix works best for you. I’ve listed the ingredients I use and the advantages of using them along with links where to buy them. You will find the recipe near the bottom followed by some YouTube videos of other mixes.

DISCLAIMER: I am an Amazon Associate so if you click on an Amazon link I might receive a commission. I am not an associate for any other products mentioned. I like those products and those are the products I use.

Hoya Mix Recipe

Hoya mix videos from some of my favorite YouTube hosts

I started collecting Hoyas in the spring of 2021. I scoured the internet for the best Hoya potting mixes and experimented on my own with combinations of soils and amendments. New plants I ordered off the internet started arriving in coconut chips and they did well for me when I kept them in that mix. This is when I started experimenting with soil-free mixes and came up with the mix below. This is the one that works for me and I’m sticking with it for now. 

Coconut coir is derived from coconut fibers and was once considered a waste product but has found new life in the houseplant and gardening industry. It is used in potting mixes and is becoming a popular soil amendment due to it’s fairly neutral pH, water retention capacity and lightweight texture. It is becoming a popular, environmentally friendly replacement for peat-based mixes. 

There are many different products on the market. I purchased a bag of 80 mm coconut coir disks from a random Amazon seller in 2021 and that seller is no longer active so I’ll have to find a new one. I recently purchased 80mm disks from Plantonix but they were thinner and did not produce the same quantity so I switched to the Plantonix bricks. 

Coconut husk chips also help with aeration and drainage. They mimic the natural conditions where Hoyas grow and give epiphytic roots something more bark-like to cling to. Coconut chips add excellent drainage while retaining water and biodegrade slower than bark. They add chunkiness to the mix and add encourage root vitality. Like coconut coir they provide a neutral pH.

When I first started looking for coconut chips they were harder to find in large quantities and seemed to be available mostly through pet stores where they’re sold as reptile bedding. I’ve been purchasing 3 different sizes from ReptiChip: MicroChip, BabiChip and RediChip. I add one cup each to my mix. I like the different size chips. In my mind they absorb and release water at different rates but I may be wrong about that. 

More recently, the garden variety chips are available everywhere, however, they tend to be sold in 10 lb blocks that have to be hydrated and broke apart. It also makes about 16 gallons of chips that have to be stored. Since I only need a small quantity at a time ReptiChip makes more sense for me

Fern tree fiber is a stick like material that enhances aeration and provides organic matter to the mix. It helps break up the coconut coir to prevent clumping when wet. It’s lightweight and contributes to good drainage. Tree fern fiber is also very resistant to breaking down and decays slowly even in high humidity. It also keeps the mix from compacting around the roots. It’s an ideal substrate for long term use for epiphytic plants such as Hoyas. 

Until recently semi-hydro was my most successful method for rooting cuttings with a healthy set of roots with lots of branching. But eventually the plant growth stalls and the only way to get it going again is to disrupt the roots and move it to a better mix. My last batch of cuttings I rooted in my Hoya mix and it has worked great.  The cuttings take about 3-4 weeks to firmly root but I don’t have to disturb the new roots and repot just as new growth is sprouting. 

I buy tree fern fiber from Josh’s Frogs. You can also find it from Fernwood.

Pumice is fabulous! I use pumice instead of perlite because it doesn’t break down easily. Pumice is a very light glass formed by the rapid cooling of lava from volcanoes. It is is full of small holes. It is a porous material that improves drainage and aeration in the mix. Pumice aids in the storage of water and nutrients- making them available to roots as needed. It helps prevent waterlogged soil and oxygenates the roots. Epiphytic roots are normally clinging to trees and exposed to the air in the wet tropical biome. They need oxygen to survive. 

I buy pumice from Bonsai Jack. I like the uniform 1/4 inch size. It’s pre-washed and there is very little dust in the bag.

Charcoal is something I’ve only added recently. I noticed it in other mixes and decided to give it a try. Charcoal is a lightweight chunky additive that aids in reducing the risk of root rot by keeping the mix well-aerated and absorbing impurities. It also helps to maintain a slightly acidic pH, which many Hoyas prefer.

Charcoal absorbs moisture and nutrients and releases them slowly over time. Charcoal is naturally anti-microbial and hinders the growth of soil fungi and absorbs other toxins from soil. A little bit yields big improvements and no more than 10% of your mix should be charcoal.

According to Bonsai Jack’s website “Horticultural Charcoal is a soil ingredient with amazing CEC properties.” 

So, I had to Google, “What are horticultural CEC properties?” CEC’s are the cation exchange capacity. I would like to thank the University of Georgia Extension for a wonderfully informative article on the subject. 

Circular 1040: Cation Exchange Capacity and Base Saturation

Soil clay minerals and organic matter tend to be negatively charged, thus attracting positively charged ions (cations) on their surfaces by electrostatic forces. As a result, the cations remain within the soil root zone and are not easily lost through leaching. The adsorbed cations may easily exchange with other cations in the soil solution, hence the term “cation exchange.” The adsorbed cations replenish the ions in the soil solution when concentrations decrease due to uptake by plant roots. The nutrient cations plants use in the largest amounts are potassium (K⁺), calcium (Ca²⁺) and magnesium (Mg²⁺). Other cations adsorbed on exchange sites are ammonium (NH₄⁺), sodium (Na⁺), hydrogen (H⁺), aluminum (Al³⁺), iron (Fe²⁺ or Fe³⁺), manganese (Mn²⁺), copper (Cu²⁺) and zinc (Zn²⁺).

A soilless Hoya mix has little organic material. The horticultural charcoal aids in the retention of nutrients in the potting mix and makes the available for uptake by the plant’s root system. I purchase Bonsai Jack Horticultural Charcoal. I like the 1/4 inch size and low quantity of dust in the bag. I’m trying out CharBliss by Plantonix. Their biochar is smaller in particle size but but seems to be a suitable substitution for the charcoal.

Two more products I buy from Bonsai Jack are Pine Bark Fines and Douglas Fir Bark Fines.

Pine Bark Fines add organic matter to the mix and help retain water. The larger particles add chunkiness and help speed up water drainage. It has a pH of 4.3 which increases the acidity of the mix just a little bit.

Douglas Fir Bark Fines also adds organic matter to the mix and help retain water. Douglas Fir biodegrades slower than Fir due to the thicker particle size. It has a pH of 5.2 which helps increase the acidity of the mix.

6 cups coconut coir
3 cups coconut chips (1 cup each RediChip, BabiChip and MicroChip)
1 1/2 cup tree fern fiber
1/2 cup pumice
1/4 cup horticultural charcoal or CharBliss
1/4 cup pine bark fines
1/4 cup fir bark fines

Mix ingredients well in a large mixing bowl before using. The coconut coir and tree fern fiber tend to fall to the bottom.

Hydrate the amount of mix you intend to use first before adding plants.

If repotting a plant from soil to soilless Hoya mix be sure to get as much dirt off the roots as possible. Soil will retain more moisture longer than a soilless mix and too much soil around the roots can lead to root rot.

A soilless mix contains no nutrients. Water each time with lightly fertilized water. Mix one gallon of water with 1/4 tsp. water soluble fertilizer such as Miracle-Gro  Azalea, Camellia, and Rhododendron Plant Food or Jack’s Classic Orchid Special with Micronutrients. Hoyas are not heavy feeders and many fertilizers work equally well. 

When using soilless Hoya mix to root cuttings first dip the cuttings first in a little water and then in a rooting hormone powder such as Garden Safe Take Root before sticking them into the mix. 

Use 3″-4″ grow pots. The roots will grow first and fill the pot before the plant starts to grow up top. 

Place the grow pot in a small tray and keep a little water in it for the first 3-4 weeks. The mix should remain moist, but not soggy, until the roots start to grow. 

Once you can tug lightly on the cutting and it doesn’t budge the cutting is rooted and you can allow the mix to dry out between waterings. 

If you miss a watering and the mix dries out just hydrate the mix and the cutting will continue rooting. Most Hoyas a pretty forgiving.

Check out some of the videos below potting mixes used by some of my favorite YouTube hosts.

https://youtu.be/xQ4vcZ8UAJ0 https://youtu.be/HNfYMz8oTDs https://youtu.be/GogxNJT1aQc https://youtu.be/eBUwFBa543s