Cultivation mistakes to avoid.

Sometimes it is easier to explain what not do rather than what to do to make Lithops flourish. So here is a non exhaustive list (probably in order of effectiveness ) of things that you could do to torture or even kill them. On the contrary, if you steer clear of these, you might end up with a very good looking Lithops collection.

1. Baking them (apart from stir fry)

High ambient temperature (40C), direct sunlight and no ventilation or air flow is a killer combination. It is probably the single quickest passive way to kill them. Two to three hours and they are gone, first turn white as the chlorophyll bleach out and then turning to mush. Sometimes bleached plants will deteriorate slowly as resource levels are depleted in the absence of photosynthesis. Plants may also exude a blood like substance. Plants directly behind closed glass such as window sills receiving too much light are places where this might occur. Small terrariums and care other places. My one green house often reach 55C in summer. Even with some ventilation one can suffer losses. A covering of 40% shade mesh add adequate relieve in the form of protecting from incident sun. The net should not contact the the plants or it will bake them as well. The colony of L. aucampuiea ssp eunicea var fluminalis I visited in habitat where all growing on the ENE side of side of shrubs, meaning that they would receive shade once ambient and soil temperatures peaked. An added benefit of this arrangement is that the plants are collectors of dew, mist and light precipitation that ends up in at the base of the shrubs.

Having pots exposed to harsh incident sun in a green house environment can be equally problematic. I once lost a row of about 10 pots on the side of my bench facing my open green house door even with ventilation.

2. Keeping the substrate constantly wet.

This will not kill them as quickly as baking them described above but it is equally effective in messing them up in the long term. While it takes a focused and persistent approach to kill Lithops with this method , once it gets going it is pretty fast as plants collapse from rot overnight. There are several reasons by a substrate may stay to wet for long:

• Too much water retentive material such as peat or compost.
• Too fine formulation of the substrate, especially in deep pots. Small (<2mm), even if in-organic tend to support a “water table” at the bottom of the pot. In small pots the effect of evaporation quickly deplete this water table but not so in big pots. To test for presence of water table, water some houseplant until the water runs out the bottoms and it appears to have drained completely. Now tilt the pot or shake it. Often extra water come out; water that was held in the water-table that remain at fixed height for the particle size distribution of the substrate. This “water table” is the major difference between containerized plants and plant in habitat soil. At particle sizes of 5mm the water table height is almost reduced to zero.
• High humidity.
• Low ambient temperature.
• No drainage holes (we will elaborate on this as separately topic).
• No ventilation – air movement dries substrate out faster,
• A fine decorative cover – it inhibits evaporation.
• Growing with plants that needs much more water (I did not say other Lithops or split rocks), but that is just a ridiculous thing to do and you would not be so stupid.

So why is too much water such a big issue? There might be several factors that I can imagine:

• Moist conditions favour the proliferation of (fungal) pathogens. Intermittent dryer conditions are effective to disrupt or interrupt the life cycle of such pathogens.
• Moist compost or partially decomposed organic material close the surface attracts fungus gnats. These critters can carry the “damping off” disease Pythium and their larvae can severely damage roots. (https://www.almanac.com/pest/fungus-gnats)
• Anaerobic conditions (i.e. poorly drained soil) robs plants of proper gas exchange a root level. The effect is compromised physiological and metabolic processes that in turn tends to compromise the plants health. Healthy living plants in general produce their own anti-fungal compounds. Ever wondered why primary decomposing fungi is not all over the trees in a forest but only the ones that have been compromised in some way?

I believe many plants that rot on the hands of new owners have probably been already compromised and weakened in the prior weeks. One or two excessive watering on an otherwise healthy well- cultivated plant is not going to kill it.

Plant that have lost root mass due to over-watering damage will not be able to absorb water – even if the substrate is wet. This will manifest as as lack of water as well – which is kind of spot on but in a non-intuitive way.

3. Cultivating in too low light levels.

The pot of Lithops might look cool on the coffee table but what is the light levels there? Keep in mind that the human eye is very adaptable and it is difficult to accurately judge light intensity. The majority of Lithops grown indoors by beginners are receiving too little light. It will need at least 5 hours or good quality light each day. A quick sign of too little light is etiolation or elongation of the body, which looks ugly but is not fatal in itself.

Often too low light levels runs hand in hand with other factors like too wet substrate for too long well. Lack of light reduces photosynthesis levels and compromise plant health and it’s ability to fend of pathogens.

4. Lack of drainage holes

The issue with no drainage holes goes further than poor drainage and a saturated substrate. Most tap water sources contain a certain amount of dissolves solids. Continuous addition of little bits of water results in a gradual build-up of salts in the soil. Plants are picky – they have their own required ratios of mineral salts to absorb and the rest remains in the substrate. Eventually the concentration of these salts could become so high that the osmotic potential become skewed such that roots can not absorb water and water can move in reverse from the plant to the soil causing dehydration. Having drainage holes and a suitable substrate will enable heavy watering from time to time to wash out any salt built-up. Brackish substrate can hence manifest as lack of of water.

5. Lack of watering

As with any living organism, water is a critical resource of healthy Lithops. Although these plants are very water wise, resilient and can survive long droughts, lack of watering for months can take it’s toll on plants. The most common reasons why plants are not watered sufficiently are:

• The folklore that Lithops only need water once or twice a year. Although they can survive this for several years, plant will become smaller after every leave changes. Professor Cole noticed this in habitat as well. Even in the most dire environmental conditions, plant would continue to do a leave change every year but the head would become smaller and smaller. In cultivation our aim is to grow plants to look better than in nature. With some genera we manage and with others we fail miserably.
• Any device like eye droppers and teaspoon watering fetish spells long term suffering. You should saturate the pots from time to time until water runs out the bottom. Your soil mix should be such that it dries off within 3-4 days max.
• Sitting and looking for it to finish splitting for 9 years before giving it water. In many cases, warm temperatures and some water in spring kicks the plant’s metabolism into gear, it starts growing and it completes the leave renewal process. You can have a look here for the effect of watering while splitting.

6. Lack of feeding

As with all other energy transfer mechanisms the leave renewal process in an inert growing medium will see plants decline over the years. For this reason some nutrient addition is required from time to time. More about this in a later post once I have run some more experiments to quantify and show the effects.

7. Lack of pest management

The most common pest I have encountered is root meally bugs. They can go undetected for months and wreck havoc under ground by damage roots and the meristem area. In South Africa it can be treated systematically and preventatively by watering once a year with Imidachlorprid solution at 2ml concentrate (360g/L) per Liter water. Please handle these responsibly and prevent exposure to other beneficial insects like bees. When it meallies are visible during transplant, rinse in a weak Malasol (Mercaptothion) solution.