Growing Hoyas as Garden Plants in the Tropics

Hoyas are grown throughout the world for their beautiful flowers and exotic scents. In temperate climates they are usually grown as indoor or hothouse plants, but in the tropics we are lucky enough to be able to grow them outside throughout the year. And given the right conditions, they can be grown as a hardy garden plant that is relatively pest resistant. 

Hoyas in the Philippines, where I live, are latecomer garden plants. It’s not so long ago that asking for a hoya in a garden center or nursery would draw a blank response — most times nobody would know it. However, that was a decade ago, but now it’s been a byword in gardens and online sellers for the last five years. The Covid pandemic further aggravated the craze and transformed the lockdowns to a positive endeavor. 

Not only the previous gardeners go into purposive garden developments and ornamental collecting, but career professionals and ‘work from home’ folks also got into plant collections. The phrases “plant addicts” and “stress relievers” evolved as common terms in social media, and these all pertain to ornamentals including hoyas. 

I have had hoya collections since 2010, so am not bitten by the craze. Beginners, now termed “newbies” already call me a hoya expert even if that is not really very true. I can just tell them experiences they can learn from or the identification of those they got from ambulant online sellers, who themselves do not bother to learn hoya names. They were also induced to gather, or grow, or collect as an immediate source of cash in the cash difficult Covid era. 

Hoya prices have skyrocketed in my country because of very high demand. Hobbyists even have a joke that hoyas are addictive, virulent, and even contagious. Although a joke, it is substantiated by the very high price which not only doubled but increased exponentially this year compared to their prices in 2015. The norm in selling propagations is a rooted, one-node cutting with just a pair of leaves. Imagine if you are buying an already flowering mother plant! ‘Exorbitant price’ is the term, but there are still some who can afford to get all the available species not yet in their collections. 

Hoya Characteristics

Hoyas are commonly called wax plants because that’s how the flowers look like, or even like ceramics. The Philippines is acknowledged to be the center of hoya biodiversity because more than 200 species are endemic here with others still unidentified. There are also species found in Papua New Guinea, Australia and other countries in Southeast Asia. Hoyas are mostly epiphytes climbing on trees or whatever they cling on for support. Some species though are bushy, some grow in mangrove forests or on rocky cliff crevices. 

Hoya flowers normally arise in umbels blooming mostly in the late afternoon. These are accompanied by scents from their nectar that range from pleasantly sweet to awful. But these scent descriptions are by humans, they are otherwise always pleasant to the target pollinators. Nocturnal insects like moths are assumed to pollinate them, making hoyas more diverse in nature. 

Before they become known and commercialized here in my country, they were already found and traded in nurseries of foreign collectors and enthusiasts. Despite their natural tropical habitat, they acclimate well in cold countries, where they are grown indoors with grow lights, aerators, and even heating mats to simulate the tropical conditions. 

Some of the earliest big collectors were in very cold areas in Sweden and United States. They really learned to culturally manage their hoyas to their preferred settings, their plants looking so lush, growing healthy and flowering well.  Despite being late, the Philippines is fast following the example of foreign counterparts. 

Media and Nutrition Requirements

The foremost common media requirement of hoyas is for it to be loose and well-draining. They get root rots in long wet conditions. Growers from different environmental conditions have their own concoctions, which include coconut husk chips, cubes, coir and cocopeat. Other inclusions are carbonized rice hulls, chopped sea shells, pumice or perlite and vermicast or composted cow manure. These materials are mixed in different ratios to achieve the fast-draining requirement.

Many growers both in Thailand and the Philippines use purely coconut husk chips or cubes. Areas with higher rainfall distribution lessen the coconut chips, increase coir proportions, and add pumice or perlite. In very dry environments with a long dry season like in my place, I use pure coconut chips. Sometimes I add perlite or pumice and dry organic manure depending on species requirements. 

Fertilization is not very intensive for hoyas.  A slow-release fertilizer (e.g. Osmocote) with 14-14-14 analysis can be used once every 3 months for newly growing plants. Other very fast-growing species can use slow-release granules with higher N proportion. This is in addition to the organic compost mixed in the media which is assumed to have higher nitrogen. Foliar fertilization with trace elements and minerals can be done every 2-3 months as well. 

Bigger plants or about-to-flower plants can be sprayed with foliar fertilizers with higher phosphorus to encourage flowering (e.g. 10-30-10 or 5-10-3 ratio or other analysis with higher P). Maintenance fertilizers can just be the slow release 14-14-14, while flower boosting fertilizers can be done every 2-3 months. 

Hoya Culture Styles

1. Hanging Method

One of the oldest early inhabitant hoyas in home gardens here in my country is the Hoya carnosa. It was appropriately known as grandmother’s hoya because adults now recall that as little girls their grandma put the individual flowers on them as earrings. It is not an endemic hoya though, because literatures say it is from China. 

It is a typical hoya that fits as a hanging plant especially in the Philippines where they are mostly grown outdoors in natural conditions. They are also exposed to natural pests and diseases and other extreme conditions. It is a lesser maintenance hoya, a very prolific bloomer and has lovely light pink flowers. 

Hanging hoyas gives easier maneuverability during natural disasters like strong typhoons or volcanic eruptions. It also saves space and is easily transported if sold. Another popular and easy-to-grow species in my country is Hoya celata which has white flowers. 

Hoyas are also known to be more prolific and flower earlier when root bound.  A 3-4 ins diameter pot is common for smaller plants, but bigger mother plants are transplanted into 6-8 ins pots when needed. Smaller pots lessen maintenance costs for media, fertilizer, water and pesticides. They are also good space savers.  Even disposable plastic containers easily lend to this method.

Another example of a hanging method is used for an Australian native, Hoya macgillivrayi. It is one of the biggest hoya flowers and one of the most beautiful hoyas in my collection. It also stays open for a week and is beautiful from all angles, below, above or at the sides. It originated from northeastern Queensland and is named after its collector William David Kerr Macgillivray.  

2. Climbing Natural Trellis

The natural characteristics of vining hoyas is to climb whatever vertical support they encounter, just like when they were still in the forest. Hoyas always want to climb up, so other live plants in the garden can be used as live trellises. Choosing which live tree, however, is important because a tree with dense canopy will restrict the sunlight from reaching the hoyas. So an open or slightly open canopy is good as a live trellis. This can also be simulated with steel trellises specially designed for them, with the trellises placed under the partial shade of natural big trees. Arbors and patios can provide this trellis style.  

Hoya diversifolia is fast growing with long internodes enabling it to easily climb two-storey high trees. It needs favorable full sun the whole day for early flowering.  We have other fruit trees nearby, but only the lanzones tree suits the needs of this hoya. The flower umbels sprout at almost every node immediately after the first heavy rains. The owner will never ask for more. 

3. Man-made Trellises and Stakes 

Many designs have been tried for hoya trellises and stakes made from steel, pipes or wood. There are arcs, cones, arbors and they vary in size depending on the area and preference.  

Bushy type hoyas do not grow long as the vining-types. In domestic gardens they can be planted in pots with trellises or stakes to keep them upright.  Some of these types are Hoya multiflora, H. linavergarae, H. odorata, H. paziae and H. cumingiana. Prolific bloomers produce umbels in consecutive nodes that truly inspire hobbyists and collectors

3. Fence or Wall Method

When bigger areas allow, the fence method is not only easily maintained but also a beautiful way to display more hoyas. They can be along a garden walkway or near a wall. The wider the hoya wall or fence, the better. Flower display will be more fascinating as they accompany you through your walk. However, it’s best to grow only a single species on this type of support. 

A friend with level flat land made theirs with Hoya pubicalyx, a very fast growing and low maintenance hoya. Its umbels are also big and stay on the vine for at least a week. My area has gradual downward gradient where I planted seedlings of Hoya buotii. I let them climb vertically between lanzones and coffee trees. They just naturally intertwined among themselves and I just let them be. 

Your method of growing hoyas will be your choice, depending on your design and cultivation preferences. Whatever your choice is, the outcome will always be beautiful and stress relieving, and for some, can be income generating. So, let’s join others in this enjoyable addiction of hoya growing.