Succulent cultivation

Article index:

* A few basic cultivation guidelines.
* Propagating Haworthias from seed.
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A few basic cultivation guidelines:

The study and cultivation of succulent plants started as a hobby more than thirty years ago and became a prominent aspect of my life.  Ever since I have never been without a small greenhouse filled with a collection of rare and attractive kinds of succulent plants. I always tried to keep the collection small and within limits of available free time to attend to it. Another self-imposed 'golden rule' I have always tried to strictly adhere to was not to keep any plants that I do not propagate. Part of the pleasure of the hobby has always been to propagate these wonderful 'living sculptures' by seed and cuttings. The resulting seedlings and vegetative propagations have always been shared with other hobbyists and made available to succulent nurseries. 
I truly believe that propagation is one of the best ways of conservation. 

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The five most important ingredients of a successful growing recipe for succulent plants are:
1) A good soil mix,  2) correct watering 3) correct light 4) correct temperature and 5) sufficient ventilation.

1) THE SOIL MIX :
* It must drain well . 
* It must be porous and allow air to reach the roots.
When the soil becomes impenetrable to air the roots of succulents literally suffocate.They will die and start rotting soon afterwards and the rot will spread upwards to the plant body above ground.. 
Both above essential requirements are easily obtained by simply adding coarse drainage material to the mix. 
Composition of a good soil mix:
The basic skeleton recipe for a good soil mix is therefore as follows:
1) 40% nutritious substance. ( peat, coir, sifted potting soil or sifted topsoil)
2) 60% drainage material. ( coarse sand, pumice, perlite or gravel.)

There is one additional recommendation that need to be mentioned here and that is the addition of a layer of top-dressing of coarse gravel or even bark chips if gravel is not available. 
It protects the lower part of the plant from mud splashing against it when watered and it improves the water penetration into the soil. It reflects heat from the sun and helps to keep the roots cooler. It also prevents a surface crust to develop on top of the soil mix.

2) WATERING:

The  golden rule for watering succulents during their growing season is to wait until the soil around the roots is dry before re-watering.
But people are often confused regarding the growing season by the terms ‘winter growing succulents’ and 'summer growing succulents’.
It is so that some succulents grow in areas that receive rain mainly in winter while the majority grow in summer rainfall areas.
This sounds as if it is absolutely essential to know where each type of plant grows in the wild and when the active growing period of a plant is. 
Don’t despair  as it is less complicated than it sounds : In general spring and autumn are the two peak periods of growth for both winter and summer rainfall succulents. 
It works like this : summer growers start growing in spring and slow down during the hottest part of summer and then pick up growth again during fall just before going dormant.
Winter growers start growing in fall and slow down during the coldest part of winter and pick up growth rate again during the early part of spring before shutting down for dormancy during summer.

A shriveled plant during the growing season is generally a sign that it needs some water. A shriveled plant during the dormant season is a sign of a resting plant and there is no need for concern about the wrinkled skin ! 

3) LIGHT:

A common misconception regarding succulents is that they love as much direct sunlight as possible. This is not true. In fact, in the wild many of the smaller species will be found growing in the filtered shade of shrubs and bushes.
In addition, many succulents photosynthesize from their stem surfaces which cause them to be very sensitive to how they are being struck by direct sunlight. Many stem succulents will lean into the direction of the strongest light in an effort to reduce the stem surface area exposed to direct sunlight.  This feature is referred to as photo-tropism.
This should be taken in consideration in particular when outdoor succulents are being transplanted. The ideal is that it gets transplanted with the same side facing the sun and be given 50% extra filtered shade for a few months until fully re-established.

4) TEMPERATURE:

Most succulents thrive best in a subtropical area with mild to warm winter days ( between 14º C and 25 º C) and cool to cold winter nights ( preferably between 4º C and 10º C). The important provision is that the minimum temperature should not drop much below 0º C and if it does, not for longer than an hour or two at the most.
In terms of summer temperatures they prefer warm to hot days ( 25 º to 38 ºC)  with mild to cool nights ( 14º C to 20º C). 
Most succulents do not like high overnight temperatures above 24º C and are noticeably absent from regions that experience such tropical conditions in summer. 
To understand this, one must understand the unique form of photosynthesis found in succulents, known as Crassulacean Acid Metabolism, commonly referred to as CAM .
Almost exactly opposite to normal plants, in succulents the breathing pores (stomata) on the leaves and stems of succulents remain closed during the day and open at night. Only during the cool darkness of night do these plants take air in from which the carbon dioxide is then extracted to be fixed by organic acids. This could be described as a kind of 'delayed photosynthesis' because the carbon dioxide is taken up in the dark. That is why cool temperature and fresh air is required at night.

5) VENTILATION:

Ambient moving air is essential to succulents and, as mentioned above, particularly overnight. 
When succulents are grown inside an enclosed greenhouse then it is absolutely necessary to install fans to create air circulation. 
This all means that unfortunately most succulents do not survive well on an office desk or windowsill despite being such beautiful indoor ornaments. They may survive the stale air situation for a long time but such a situation is just a drawn-out death sentence to such a plant.

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Propagating Haworthias from seed.

(Note : Posted article on Haworthia Hybrids contains detailed information regarding my pollination methods for Haworthia flowers. )

In my experience, the following seem to be the main factors that enable successful germination of Haworthia seeds:

·         The seeds must be fresh, preferably not older than 6 months.

·         The best germination temperature conditions for most species are warm days and relatively cool nights. If the minimum night temperatures do not drop below 20ºC (68, ºF) seeds may not germinate. Some strict winter growers (mostly species that flower in mid to late summer) seem to demand overnight minimums of below 15ºC (59ºF).

·         Germination is best when seeds are sown densely, so it is very beneficial to have a quantity of seeds to sow.

This is my own method explained and illustrated:

·         Cleaning of seeds: best is to remove all dry fruit shells and debris between the seeds. If sown together with seeds such items may develop fungus which will spread to the seeds and seedlings.

Remove all seed shells and other debris before sowing.

·          Soil mix for sowing:

1 part perlite, 1 part vermiculite, 1 part fine sifted compost (leaf-mold or coir or peat) and 1 part river sand (quartzite sand is best, not saline beach sand).

·         Container:

The pot need not be deep and can be as shallow as 2cm as Haworthia seedlings do not develop deep roots within their first year. Drainage holes at bottom essential.

Eighteen month old Haworthia seedlings still growing happy end densely crowded in a shallow 25 mm deep tray.

Fill with soil mix and press down lightly to form a flat surface for sowing.

·         Place label in pot and sow seeds densely on top of mix.

·         Using an atomizer or mist sprayer, gently wet seeds from above allowing them to stick to the surface.  Use water (preferably distilled or rainwater) with very tiny amount of fungicide added.

·         Add a very thin layer of coarse sand or coarse peat debris to cover the seeds. This is optional as seeds will germinate without any covering on top.

·         Spray again using the mist spray with water containing a small amount of fungicide and spray until water start running from drainage holes at bottom of container.

·         Keep in light but shaded place under transparent cover to insulate humidity. A spot below 80% shade cloth is ideal.

·         Give mist spray (with fungicide water) early mornings and in early evenings daily and keep transparent plastic or glass cover on to insulate the humidity until the seedlings start germinating (takes 5 to 15 days on average).

·         As soon as first seedlings germinate, remove plastic/ glass cover otherwise germinated seedlings may rot. Keep up the morning and evening mist spray routine until all seeds are germinated. Mist spray routine can now be reduced to early mornings only and even be skipped occasionally. 

Freshly sown seed pots are covered with plastic to insulate humidity. I use wooden frames covered with offcuts of greenhouse plastic.

Once seeds germinated, the plastic covering is removed and replaced with shade cloth-covered frames to keep seedlings well shaded for another two or three months before exposed to stronger light.

Explanatory comments:

·         I prefer to use a mist spray from the top to wet the soil instead of standing the pot in water to soak up moisture from below. There is nothing wrong with the latter procedure but I do suspect watering from above from the start does improve the drainage capacity of the soil. I believe that such gentle watering from above helps to prevent compacting of the soil and improve capillary action.

·         Some fungicides may inhibit germination (such fungicides can of course safely be used after seedlings have germinated). I use Funginex which does not seem to influence seed germination at all but I use less than half the recommended dosage in the mist spray application for germinating seeds and young seedlings.

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Haworthia leaf-propagation.

Herewith a few illustrated steps explaining my own method for removing lower leaves from Haworthia plants without affecting the beauty and appearance of the plant much. After a few of the turgid lower leaves have been removed, the plant can be re-potted but the fresh wounds around the base of the plant should not be exposed to wet soil immediately. I often fill the pot with soil to cover the roots ( and prevent drying out) but only to below the area where the leaves have been removed. After a few days when the leaf-base wounds have healed, I add a gritty layer of soil and some to-dressing gravel and water normally. 

Removing leaves for propagation:

* Best is to remove the plant from the pot as it is too difficult to reach the lower leaves properly while the plant is in soil.

* Remove the lowest dead and half-dead shrivelling leaves. Only leaves that are still turgid will be useable for leaf-propagation.

* Haworthia leaves are 'anchored' at the base on both sides by a thin skin / membrane that is a bit difficult to tear. It is best to use a knife and just slightly cut the ends of these thin leaf-base sides on both sides. Only a small cut to loosen the leaf at both ends is necessary:

* The next step is just to twist the leaf sideways but VERY slowly to allow it to tear gradually away from the stem. The slower one does this, the better the chances are of getting the leaf to break away containing parts of the opaque white stem tissue. It is necessary that the break must contain some of this white stem tissue for best results.

* In this case only half of the broken off base contain some of this tissue but it is fine, the roots will develop from this white opaque area and soon afterwards small plants will develop from the same area.

I normally dip the freshly broken leaf base in rooting hormone powder and allow the leaves to lie in a dry shaded place for about a week or two.

Afterwards I simply allow them to stand on top of a soil mix leaning against the side of a pot and the adding of coarse gravel around them helps to keep them upright. I keep the pot in filtered shade (amongst young seedlings) and keep the soil moist. Roots will appear within a few weeks and after two or three months small plants may start developing.

The advantage of leaf-propagation is that a treasured clone can be duplicated and in some cases up to 6 tiny plants can develop from a single leaf. However, the average number of plantlets forming is 2 or 3.

A rare freak case of a plant developing from inside the rooted leaf ! ( Haworthia bayeri).