Haworthia Cultivation (David Martin)

Author: David Martin


David E. Martin was the owner of haworthia.com from 2000 to 2016. He had devoted to building a comprehensive web database of Haworthia species with photos taken from his greenhouse. Many growers from worldwide referred to these photos and his famous article Haworthia Cultivation based on his own growing experience.

Martin’s interest in Haworthia started in 1974 when he built a succulent greenhouse. That interest was put on hold for 22 years when the job required him to move and leave the greenhouse behind. In 1999 he built a new greenhouse in his backyard and started over again. In May 2004, Martin spent two weeks in South Africa studying and enjoying Haworthias in the wild. There he traveled with Scott McDermott from Tucson and they were guided by Gerhard Marx.

David: My greenhouse is in my yard in Broomfield, Colorado, just outside Denver. I built it in the summer of 1999. I specialize in Haworthia, with about 500 adult plants and many, many seedlings. This is where I go to enjoy these plants.
© David Martin
David: My greenhouse is in my yard in Broomfield, Colorado, just outside Denver. I built it in the summer of 1999. I specialize in Haworthia, with about 500 adult plants and many, many seedlings. This is where I go to enjoy these plants.

Haworthias will grow under many different conditions, but they grow best if given lots of light, with water only at the appropriate time. One overall formula as to when to water, how to water, what soil to use, and when to fertilize, will not work. Because where you grow your Haworthias will determine how you approach these issues. For example, Haworthias grown on a windowsill in Moscow will require a different treatment compared to those grown in a greenhouse in Tucson. All is not lost however, because as you dig deeper and look at what the plant’s needs and then take into consideration your local conditions, you will grow beautiful Haworthias.

Choosing a pot for your Haworthia

Lets start with the pot. Use a terra-cotta clay pot if you live in a colder wet climate and a plastic pot if your area is hot and dry. The unfired terra-cotta clay will breath and allow moisture to escape more easily in a wet climate, while the plastic will preserve the moisture for the plant’s roots in a dry climate. The idea is to create an environment for your Haworthia that will allow the plant to dry out after it has been watered, as remaining wet for too long will cause root rot during periods of dormancy. Pot size is important here also. If your world is cool and wet, an undersized pot will dry more quickly than a larger size, and that is good. However, if you grow in a hot dry climate, it may make more sense to pot in larger pots that dry more slowly. Some growers plant in very large pots and simply put a bunch of plants in large pots and even in trays, taking up about the same space per plant as smaller pots would.

Soil Selection

There are several rules that should be followed. The soil should be free draining, meaning that it is porous. This can be accomplished by making a potting soil using as a component materials such as; perlite, pea sized pumice, or even pea gravel. The trick here is to produce a soil that has some organic mater, but not so much that it becomes water logged and rots your plants roots. I use 1/3 pumice (pea sized) 1/3 perlite, and 1/3 potting soil, which consists mostly of leaf litter. This works if I am careful not to water when I expect an extended cold or cloudy period. The soil, and its moisture holding capacity, must be considered when watering. A lot of water on a hot summer day with many more hot days in the forecast is probably necessary, while even a little watering during a very cold damp time, might be too much.

Putting your Haworthia in a Pot

Plug the hole in the bottom with a layer of porous paper towel. It will decompose in a year or two, by the time the roots are holding the soil firmly in the pot. Hold the Haworthia with one hand and place soil into the pot around the Haworthia. Place the soil loosely around the roots and then pack it down by striking on the side and by gently packing around the plant until the soil is firm and the Haworthia is comfortably potted. I try to leave a 1/2″ to 1/4″ of pot rim so water will not overflow too easily.

I next use a top dressing, but it is not required. Top dressing is a layer of stones or gravel that give the soil a nice appearance. Its advantages are the obvious esthetic one, but a good layer of rock will, if properly applied, keep the plant away from the wet soil preventing rot. It will also form a barrier that discourages fungus gnats from laying their eggs in the wet soil. More on fungus gnats later. The disadvantage of a top dressing is that it becomes more difficult to determine how wet the soil is if it is protected by a layer of rock. Getting to know the weight of a wet pot and a dry pot is a good trick that will help get around this problem.

Light for your Haworthia

This plant started life in 1993 as the only pup produced by a plant I purchased in 1978. It started producing offsets in 2000 when it was first moved into a greenhouse, and it has never looked back. Today (Nov 17, 2003) it has about 20 heads, with more arriving all the time.
© David Martin
This plant started life in 1993 as the only pup produced by a plant I purchased in 1978. It started producing offsets in 2000 when it was first moved into a greenhouse, and it has never looked back. Today (Nov 17, 2003) it has about 20 heads, with more arriving all the time.

Light is in short supply, and I often see fat, green, elongated Haworthias that are distorted beyond recognition by low light levels. However some growers just prefer the big green soft Haworthias that are a result of growing in low light. If this is the case with you, it will work most of the time with most of the Haworthias, but, in my opinion, will result in a great deal of sameness. In most cases it is hard to give your Haworthia too much light. The exception here is a newly acquired tender plant that needs to harden up. To put a plant in direct sunlight that has never seen the sun will cause a fatal sunburn. If you place your Haworthias in the brightest light you have that is not direct sunlight, you will grow into very nice looking plants. For growing, a greenhouse is ideal, next choose a sunny South facing window, then an East or West facing window. Save your North windows for ferns. If a South facing window has a tremendous amount of sunlight, slow acclimate your new plants by placing several layers of a thin lacy cloth between the plant and the sun. Then slowly remove a layer at a time at three week intervals to allow the plant to adjust to the hot sun. Also remember that a plant in the windowsill is partially protected from the suns ultraviolet rays by the glass, taking a windowsill or greenhouse plant and placing it in the direct bright outdoor sunlight, for even a few minutes could burn the plant so it is disfigured for years. I recommend that any move to the outside in the summer be under the shade of a tree. If you must put your plant directly in the sun, do it very gradually, just as you would treat yourself when acquiring a suntan in the spring. If your are blessed with skin that does not burn, ask one of your pale friends for advice.

Watering your Haworthia

This is actually much easier than you might think. Here is the rule: “Water when dry, don’t water until the soil is approaching dryness.” When you water your Haworthia, go ahead and water it until water flows out the pot’s bottom hole. Then do not water again until the soil is dry. After awhile you can tell by the pot’s weight, but the best way to tell if watering is needed is to dig your finger or a pencil into the soil down to an inch or more and see if the soil is damp.

This method works very well because if you water your Haworthia and then a wet cloudy weather system sets in, it might not require watering for 4 to 6 weeks. However, in the summer, with lots of sunshine, a twice weekly watering might be required. The only caveat here is to be careful during cold wet winters, as a dead plant from rot can occur in days, while a dead plant from lack of water takes months and months and can be revived until the very end.

Fertilization of Haworthias

If you repot every few years (highly recommended) it is actually not necessary to fertilize! Your plants will grow more slowly, but no harm will be done. For optimum growth, fertilization is a good idea. However, the rule here is to fertilized only with a dilute fertilizer, and only when the Haworthias are in active growth, such as the spring and in the fall. I fertilize with a 1/4 strength solution of 20-20-20 ( nitrogen-phosphorus-potassium). The directions state that one teaspoon should be dissolved in one gallon of water, so I water with 1/4 tsp per gallon of water. Applying too much fertilizer will encourage too much foliage growth, producing grotesque plants. In the extreme, too much fertilizer will kill your Haworthias. Go easy on the fertilizer, and when in doubt don’t fertilize.

Propagation from offsets and leaves

Haworthias vary from being completely solitary to producing huge clumps of offsets. If you want to propagate a plant that produces lots of offsets, it is as simple as pulling an offset from the mother plant and sticking the offset in the dirt. If removing the baby plant from the mother produces a wound on the baby, it is a good idea to powder the wound with a rooting hormone and laying the cutting aside for a day or two to allow the wound to form a callous, then sticking the cutting into soil. Go easy on the water, keeping the soil only slightly moist until the cutting has established roots.

A successful Leaf cutting will result in growing a new plant (sometimes several plants) from a single leaf. The trick here is to get a bit of the stem tissue when you remove the leaf. If you just break a leaf from the plant and get none of the stem, the leaf will not root. The best way to get started is to un-pot the plant and wash the soil from its roots. Remove any old or dying leaves and choose a vigorous healthy leaf or more. Remove this leaf with a sharp knife making sure to cut off a bit of stem tissue with the leaf. Dip the cut end into rooting hormone powder and allow to dry in a shady area for a couple of days. Next place the leaf in a warm shady area in a pot who’s soil that is kept slightly moist. With a bit of luck, the leaf will root and one or more plantlets will emerge.

Forced offsetting

Forced offsetting is a method that you can use to force a solitary plant to produce offsets. Since all the growth in such a plant is focused into the central growth spot, if that area is destroyed, the plant will be forced to grow from secondary points, producing offsets. If the plant is a columnar plant, this can be achieved by lopping off the top, which can be rooted, producing another plant. Meanwhile the original plant will produce one or more offsets. This method is popular with H. pumila. One method used by Joseph Cheng on retused and truncata species involves a process that will give good results. First, the plant must be in good health and have good roots. Initially remove soil around the base of the stem until the stem is exposed, removing old leaves and debris. With a sharp knife, make a cut across the exposed stem above the soil level severing the whole plant from its roots. If some of the side roots and bottom parts a leaf are also cut, don’t worry, as that is almost unavoidable. The now rootless plant is then treated with rooting hormone and allowed to callous over for a few days before being re-rooted. The remaining pot with the stem stub and roots is then placed in a shaded area. Water should be withheld to the point that the soil is only slightly moist. When growth is detected, regular watering can be resumed, but do not let the pot go dry. The tip of the cut stem should be kept about 1/2 cm above soil level. If done at the beginning of the growing season, which is also the best time, the chance of seeing babies coming out from the stem and the tip of any cut roots is around 90%, as long as your are careful with water, thus preventing rot. Sometimes the cut can be made at a point where 1 or more leaf are left with the stump, if this can be accomplished your chances of offsets emerging will improve to 99%! This method will not cause any damage to the appearance of the plant and is a good way to produce more plants. Another method, especially useful with a flat rosette plant, is to destroy the growing point with a sharp knife or a hot, fine tipped soldering iron. If successful, this surgery will stop the growth in the center of the plant, forcing the plant to offset. The bad news is that you are thinking about attaching one of your prized plants with a knife! This step should practiced on some unimportant plants before you go after that trophy Haworthia!

Propagation from roots

This is a method I have never tried, but one that is used successfully by my friend Joseph Cheng, his description follows. When repotting an old retusa type, or truncata, cut off a few young fat roots, these are of lighter color. Your chances of success will drop if you try this method with old roots. Pot these roots into a slightly moist, very fine vermiculite, leaving the top half centimeter of the root exposed. Place the pot under the bench, preferably inside a greenhouse where the humidity is a high. Water should be applied very lightly, then after waiting from 3 to 12 months you should see 90% of the roots will produce one or more offsets! It is important that the root not get too dry or it will shrivel or too wet which will cause rot. This is a good method to propagate plants that never offset, and will work on any Haworthia with “fat” roots.

Free Seed from your Haworthias

This photo shows six 6-pack seedling pots (36 1-inch pots) of various Haworthias at the age of seven months.
© David Martin
This photo shows six 6-pack seedling pots (36 1-inch pots) of various Haworthias at the age of seven months.

Haworthia seed is very difficult to obtain, and when you get some, you will find that its often gives very poor germination. Further, very often and two years later, seed that did germinate will grow into something quite different from what you thought you purchased. There is another way, and that is to get seed from your own Haworthias. To get seed, two plants must be in bloom at the same time. There are exceptions as some plants “self” or fertilize themselves, but generally you need a “father” plant and a “mother” plant. The father is the pollen donor plant, and the mother is the plant that produces the fruit or seed capsule. When your plants are in full bloom, you should have a pollinating instrument ready. This can be any of the following: a cat whisker, a fiber from a large paint brush, especially those with a “fuzzy” tip, the very smallest of artist brush..this is the one with 6 fibers and is used to place infinitesimal amounts of paint on a canvas, a fiber from woven shade cloth. The “pollinating instrument” you chose should terminate with a fiber that can enter a Haworthia flower and be extracted with pollen “on board”. Please note that this is a skill that requires very fine coordination, and may require some practice to perfect. It is best to choose a flower in the second or third day after its opening to obtain pollen. Flowers in their first day will not yield pollen because the pollen hasn’t ripened yet. Flowers after the third day tend to fill with nectar that prevents pollen from being placed inside. I take pollen from flowers after the first day and then transfer that pollen into flowers on another plant. When pollinating two plants that are blooming, I move pollen back an forth from every eligible flower on plant #1 to every eligible flower on plant #2, back an forth, back and forth. If you wish to prevent cross fertilization with other Haworthias, you should isolate your blooming Haworthias to a specially prepared “bridal chamber”, a screened off area or another part of the house or greenhous that is screened off from any pollinating insect intrusions. While the plants are blooming it is best to pollinate twice a day; morning and evening are a good schedule. At the conclusion of the blooming period, watch for the development of the seed capsules. Allow these to grow and develop and before they turn brown, it is a good idea to seal them with clear tape. This is done because as the capsules ripen they dry and spill their seeds. With a bit of clear tape around the seed capsule the seeds are not lost. When the capsule splits the seeds can be planted. They will not last too long, and if not planted within a year, they will probably never germinate.

Growing Haworthias from Seed

Growing Haworthias is great fun, and growing them from seed is the ultimate experience in getting to know this diverse genus. Haworthias are fast growing when compared to some cactus, and will reach blooming size from within one or two years for most, and within five years for the slow species.

When growing Haworthias from seed, I prefer the “baggie method.” It consists of placing a pot or flat of wet sterilized soil with the seed sprinkled on the surface inside a sealed plastic bag. The reason this method is used is because the seedlings thrive in a moist environment, and if it is not provided, they can die even after a few hours of dryness on a hot day. After a few days in the baggie, the seeds will germinate and they can remain inside the for several months, until you feel comfortable to bring them out.

This method requires that everything is sterile before you begin. I use either a new baggie, or wash an old one in hot soapy water. I wash my germination pots in hot soapy water also. I sift the big sticks and rocks from my regular potting soil and use this finer soil for germination. The soil must be sterile, so it is baked for at least two hours at 250F (120C). If you are not the cook in the household, I strongly recommend that you bake your dirt when the cook is out of the house, this will help preserve any remnants of a loving relationship you may have had with the cook. While the soil is baking, boil a large covered pot of water for use later. After allowing the soil to cool, pour it into the germination flats, then soak them from below in the cooled water that was boiled earlier. Seeds are then sprinkled on the surface and the whole surface is sprayed with a fungicide (if you are brave you can skip the fungicide). The pots go into the baggie, it is sealed and placed in a location where it can receive bright light during the day (not direct sunlight) and cool nights. If you have no such bright day and cool night location, the bagged seeds grow very well under florescent lights on a timer with 14 to 20 hour “days” and 4 to 10 hour “nights.” After most of the seeds are germinated, I find that some have sent their roots along the surface of the soil instead of into the soil. I use a toothpick to make a hole for the root, then pick the seedling up with the toothpick and poke its root into the hole, packing the soil around the root with the toothpick. Watch the seedlings closely for signs of fungus and spray with fungicide if it appears. If you have a large fungal outbreak, you may have to remove the baggie prematurely to keep the fungus from eating all your seedlings. When it is time to remove the seedlings from the baggie, the removal should be gradual. For the first few days open the baggie just a little, allowing a bit of dryer air inside. Gradually open it more and more, until you can move the entire germination flat out of the baggie. For the next few months it will be a good idea to spray the seedlings every day or two, not allowing them to get too dry.

The Sick Room

If you put your doctor cap on when you find a sick Haworthia, it can often be saved. In about 90% of the cases you will discover that the plant has lost its roots. When inspecting your plants it is always a good idea to grab the plant at its base and gently try to tip it one way and the other. A very well rooted plant will be rock solid in the soil. A plant loosing its roots or just getting them back will feel loose, and a plant with no roots can be plucked from the soil with no effort. I never see a healthy, good looking plant with root loss. When a plant starts to look a bit sickly and I wiggle it, I often find that it has lost its roots or is in the process of loosing them. This often occurs when too much water was given to a plant that was dormant. it is always best to let a sleeping dog lie, and always best to underwater a dormant Haworthia. However, regardless of how hard you try, you will get sick plants. When this occurs, I suggest that you first dig the plant from the pot and wash all the soil off its roots. Then pull off all the dead and rotting roots and any old dead leaves. Then powder any wounds with rooting hormone, to stop any fungus attach and encourage new root growth. Inspect for root mealy bugs. If you find these, then you have found the problem (see below), otherwise the problem was probably one of root loss. While you are at it, notice how wet the soil was. It seems to me that sometimes I get soil that stays too wet for too long and Haworthias hate soaking wet soil. The best remedy is to repot your cleaned plant and keep it in a shaded area and keep the soil on the dry side. It is always amazing to me how many plants that I have just given up for dead that have miraculously come back to life and proven me wrong. If you adopt the slogan “never give up” you will be pleasantly surprised at how many hopeless plants you can save, no mater how “dead” they look.

Insect Pests

Mealy Bugs are evil little sucking insects that should be battled on all fronts. They should be squished, squashed, and smashed at every opportunity, an activity in which you should take glee! When you find one mealy bug, you can be sure that there are 10 others that you haven’t found. As a preventive measure, I recommend that all new plants undergo an extensive bare root inspection before joining the regular Haworthias. This inspection should check every crack and crevasse to see if you can find and eliminate any mealy bugs, especially in the roots. When I find even one mealy bug in my collection, I assume there are many more, and I treat the entire collection with a systemic insecticide. In the past when I have not done this, the infestation spreads, and I eventually must treat, but by then the problem is much worse. I know of no other way to get read of these beasties other than to treat with a systemic insecticide which kills the bugs as they suck the plants juice.

Fungus Gnats grow and breed in moist organic soil. These are tiny little gnats about 1/16″ long that are weak flyers. The trick to controlling fungus gnats is to understand their life cycle. They lay eggs in wet soil that hatch into little clear maggots that feed on organic matter and plant roots. After about 10 days, these maggots pupate and then emerge as gnats. If you are having a fungus gnat problem, your soil is probably too wet, so back off on the watering. Another way to control these gnats is to use a top dressing. By covering the soil with a gravel topping, the gnats cannot get to the soil as well to lay their eggs. I also treat the soil with Malathion Insecticide, which kills the maggots. To rid your plants of a nasty infestation, it is often necessary to drench the soil with Malathion weekly for 3 to 5 weeks.