A Comprehensive Guide to Growing Asclepiads

With a total of more than 100 genera, the botanical Asclepiadaceae family contains few species which fall into the category of “Average”.  These spectacular specimens represent a visually unique group of plants that are desirable to the most enthusiastic and dedicated of succulent growers, often presenting a challenge in their care and cultivation.  The difficulties faced in caring for and ultimately, propagating this valued plant group, only adds  to the appeal for the “hard core” collectors of the fascinating succulent world.

flowers of orcea chrystephana
Flowers of Orbea chrystephana

The most frequently seen species include the “Carrion Flowers”, otherwise known as Stapeliads.  These are often distinguished by their floral mimicry and foul-smelling fragrance, used throughout the species to attract necessary pollinators.  Ceropegia, Hoya and Orbea are a few further examples of the most distinctive and attractive floral wonders of the Asclepiad empire. Ceropegias have evolved with various different body forms, some grow twining stems whilst others scramble along the ground, natively growing through trees.  All however, grow from an underground caudex or number of underground tubers.  From a horticultural point of view, the Ceropegias are seen as relatively easy to grow. The Fockea and Raphionacme species are thick-stemmed, caudiciform succulents, which also attract a fair amount of Asclepiad enthusiasts.

Hoya maingayi
Snow white blooms of Hoya maingayi

For those of you who like a challenge and consider nature to be one of the most wondrous and fascinating subjects, then these are the plants for you.  Let us take a look at how to care for plants in the Asclepiad family.

Cultivation

Potting Soil

Planting Soils

Use a very free-draining compost for these plants, adding at least the same quantity of gritty medium to compost.  The best mediums for creating a suitable free-draining mix are Sharp Sand, Horticultural Grit and the much raved about granule material Seramis.  To reduce weight, you could replace some of the grit content with perlite or horticultural graded vermiculite.  Both of these lightweight products absorb excess water and release it slowly for your plants to use.

Quaqua confusa flower
The Delightful Quaqua confusa

What exactly is Seramis?

Seremis is a high-quality clay growing medium which in manufacturing, undergoes a special porisation process.  This process results in a small, light and granular product with extremely high-water retention properties – far more than traditional coco fibre or soil.  Its fine clay make-up and ultra- porous surface allows each granule to hold over 80% of its own weight in water, allowing excess moisture to be stored and ultimately, released again when needed.

The granules are hard, much like absorbent pebbles, therefore there are no inevitable compaction problems.  They also have a very low salt level and a natural pH value, resulting in a truly remarkable product which has to date, achieved great results.

Seramis clay substrate
Seramis clay granules

These are not to be confused with the regular hydroponic clay pellets, but are often used in specialist drip re-circulation hydroponic systems and those of passive hydroculture.

Giving your Plants the Perfect Growing Environment

Flowers of Caralluma albocastanea
Distinctive flowers of Caralluma albocastanea

Temperature Requirements

Most of the Asclepiad species natively come from very dry, arid areas but are found to thrive in cultivation when given appropriate heat and care is taken with watering.

Many will require warmer growing conditions than most plants in the Cacti family, some species requiring a minimum winter temperature of 12 degrees C, that’s 53.6 degrees F.  In general, however, a temperature of 8 – 10 degrees C, (46.4 – 50 degrees F), with a bottom heat cable is ideal.

Succulent glasshouse
An organised Succulent Glasshouse

For those of you with an unheated greenhouse, ensure to bring your plants inside over the winter months, keeping them away from cold draughts.

Light Requirements

Succulent growing is becoming far more popular and although small collections can be housed in a conservatory or a sunny, spacious window-ledge, a greenhouse or glasshouse is essential for those seriously getting into growing.

It is worth remembering that these plant groups are used to having naturally filtered light, often found growing under bushes or in natural rock crevices throughout Africa, parts of Asia and Middle Eastern Countries.  With this in mind, ensure they are placed in a bright and sunny position throughout the growing season, with adequate ventilation and a small amount of filtering to reduce  light intensity.

Scorching

Scorching, or Sunburn can cause burning and scaring your plants skin, commonly referred to as the epidermis.  It is caused by too much intense sunlight, which combined with a lack of ventilation and insufficient air movement will likely cause scaring defects and even plant death.  Tender plants are most susceptible to scorching in spring time when their tissues are still soft from their winter rest and the days become surprisingly bright.

One of the best ways to avoid scorching is to move your plants further away from the glass – whether this be in a greenhouse or indoors.  You can use a temporary shade paint to paint on the most prominent areas of your glasshouse, washing it off when your plants have had time to adapt to the light intensity and when in full growth mode.

Stapelia variegata
A superb specimen – Stapelia variegata

Ventilation Requirements

An aspect which is just as important as heating, but one which is often neglected by growing enthusiasts.  When in their natural habitat, these plants are used to adequate space and good air circulation.  A stagnant and cramped environment can cause damage to even the most arid-adapted plant species, especially in the heat.

It is worth considering using a fan heater in glasshouses throughout the winter months, leaving the fan on at all times, even when you turn the heating element off.  In the summer time, it is a good idea to keep your greenhouse well ventilated with sufficient air circulation, especially when temperatures rise to over 20 – 25 degrees C, that’s 68 – 77 degrees F.  You can continue to use your fan heater for this job, (obviously with the heating element turned off), alternatively a larger fan can be used for the summer months.

Natively, plants get used to the nightime drop in temperatures, this temperature variation is beneficial to most succulent species and allows them to exploit their C A M photosynthesis ability.  Should nigh time temperatures remain above 10 degrees C, 50 degrees F, I would recommend leaving glasshouse vents open, thus avoiding any growth problems with plants using the Crassulacean Acid Metabolism and ensuring positive growth.

Duvalia corderoyi flower
A true floral wonder – the Duvalia corderoyi

Caring for your Asclepiads

watering image

Watering

Overwatering is one of the most common reasons for plant losses, that stands throughout most of the succulent and cacti growing population.  Asclepiads need regular watering throughout he growing season, but should not become waterlogged.  Always make sure that your potting compost has dried out before watering it again.

pH Values

The pH value is a measure of acidity and alkalinity of a soil or compost.  Many cacti and succulent species are extremely sensitive to the extremities of both acid and alkaline soils, this can hamper growth and over time damage your plants.  A neutral pH value is 7, a perfect balance between an acid and alkaline reading.  For succulents, the ideal soil pH is just on the acidic side, with a pH value of around 6.  It is worth bearing in mind when feeding and watering your plants, for their well-being, neither should greatly change the pH value

Ceropegia sandersonii
A natural artform – Flowers of Ceropegia sandersonii

Feeding

Once your Asclepiad plant has a well-establish root-system, regular feeding will aid in optimal growth.  It is recommended to feed a half-strength liquid fertilizer every time you water your plants, from early spring time, right through till late summer.  I would use a liquid low-nitrate feed in periods of slow growth and a balanced liquid feed when the growth is strong.  Whichever fertilizer you choose, make sure it contains trace elements – these are vital for healthy growth and are often found lacking in succulent soils.

Pollination and Propagation

Throughout the many known genera, the pollination mechanism of the Asclepiadacea family is known to be a very complex one.  Over time, this has evolved with certain species targeting specific pollinating insects, meaning even with many plants flowering at the same time, it can be very difficult for these to set seed.

Asclepiad seeds

 

For those determined growers, there are a number of micro-techniques which can be followed for propagation, though the most common and successful method of plant multiplication is by taking cuttings.

Problems

There are a few common pests and diseases which Asclepiads need to be protected against. It is important to keep a clean and tidy growing area, removing and disposing of any diseased or decaying plant matter.  Pests and diseases can spread really quickly in both sickly plants and those which are weakened by insufficient light, over watering and the like.

Plant Pests

The main contender for this prize pest is the infamous Mealy Bug.  Though common, a Mealy Bug infestation can spread rapidly and if left untreated, eventually kill your plants.  These are small, sap-sucking insects, which leave a waxy residue on your plants and look much like a small, woolly woodlice. When checking your succulents for pests, look particularly in areas of concentrated growth as these are places, they like best – warm, moist and difficult to get to!

Mealy Bugs
Woolly Mealy bugs

For small Mealy Bug infestations, using a localized insecticide will usually remove the problem.  In larger infestations however, you may find using a systemic insecticide is your best solution.

Diseases

Fungal Infections

These can be a real problem when growing succulents in home surroundings, but less of a problem when in their natural dry environment.  Extra humidity and its associated fungi can lead to stem rot and other nasty infections which if left untreated, can cause the death of your cultivated succulents.

For stem rot there is no real cure. The damaged plant tissues should be removed with a sterilised knife and treated with sulphur powder.  After a few days in a warm and shaded spot, these can be rooted as a cutting.

Root Rot can also be a problem with succulent growing and is generally caused by over-watering, insect infestation, late potting-on and excess alkaline levels.  This can be treated by removing all affected roots, cutting them back to healthy tissue and treating them with sulphur powder.  Leave your plant in a warm and shady spot for a few days, thereafter, it can be rooted like a cutting.

Flowers of Hoya mandulidii
Flowers of Hoya mandulidii                                              Images courtesy of Pinterest

Now that I have covered pretty much all you will need to start your own Asclepiad collection, why not take a look at my previous article on the “Amazing Asclepiads”?

Be amazed by their unique array of floral displays, whilst learning a little about the history of my “Top 10 Genera” within this fascinating succulent family.