The Highland Culture Guide


 

Get the answers to your cultural questions here with our integrated approach. All of the basic elements of succulent cultivation are presented with an emphasis on how to combine them to work for you. It's not just another Do's and Don'ts list.

With this guide as a starting point you'll know why you're doing things. With a little experience you'll soon be solving your own problems and growing very good plants.

Back To Home Page

Contents

Light And Your Strategy

Temperature

Watering

Dormancy

Making Changes - Timing

Growing In Containers

Supplies: Mix, Nutrients, Containers

Pests

Basic Equipment List

 

 


 

Grow Plants Like These!

pauliana.jpg (20108 bytes)
The fabulous Euphorbia pauliana

tecta.jpg (17329 bytes)
Crassula tecta

juttae.jpg (8537 bytes)
Cyphostemma juttae - a true classic

Speak The Language

For many, entering the world of succulent plants and the people who collect and trade in them means confronting the Latin botanical nomenclature used to name and describe this natural world. Don’t be put off by this!

Learning the botanical names of your plants and how to pronounce them is essential to cultivating and building your collection. Abandon the use of common names such as “snake plant” or “pencil cactus” in favor of Sansevieria and Euphorbia. Common names are not unique and will only lead to confusion.

All you really have to know is that each plant is a single species or a hybrid of two or more species, and like species are organized into a larger single group called a genus such as Pachypodium. In turn, groups of similar genera make up the plant families such as Apocynaceae which includes the genera Pachypodium and Adenium. Genus and species in that order are used exclusively when referring to any plant. So instead of “Madagascar Palm” we use Pachypodium lamerei or Adenium obesum in place of “Desert Rose”.

Don’t be intimidated or embarrassed when attempting to pronounce these strange names. Everyone makes mistakes but with a little experience it becomes second nature. To get started you could even watch The Victory Garden on PBS where they consistently use genus and species when discussing plants of all kinds.

Light And Your Strategy

By far the single most important element for growing quality plants is available light. Succulents need serious natural light. This means a full southern exposure with nothing between your plants and the sun except possibly the window glass or greenhouse glazing. A full southern exposure is one which receives all available light for most of the day. Avoid locations which are blocked by trees or buildings.

In a perfect world, your plants would be growing in a blazing southern exposure and receiving 360 light. This would of course mean a perfectly situated greenhouse or an outside location in a frost free climate. Such facilities are impossible for many of us but this does not mean that you still can’t grow first rate quality plants. This is where your strategy is required.

Your strategy should be to give your plants the light they need when they need it. The keyword here is when. Most succulents will enter an annual dormancy period and will tolerate less than ideal light during this part of their life cycle.

If you are growing indoors, the preferred strategy is to move your plants outside during the summer months for optimum light during their growth period then winter them over in southern windows when they are dormant.

If you are restricted to indoor conditions year round, you must compromise. Regardless of how good your windows are, you will still be providing light from only one direction and there will be a few plants that will not tolerate less than ideal light. You will have to restrict your collection to those genera which will grow well in your conditions or simply move your plants to better light.

If you are growing in a greenhouse or outside in frost free conditions, sufficient light is not your problem. In many parts of the southern and southwestern U.S. your problem can be too much light and some sun filtering material is in order especially for smaller plants in small containers.

Artificial light will keep most but not all succulent plants alive but that's about it. After more than a month or two under fluorescent tubes for example, plants take on a very soft weak look and quickly lose their appeal. Artificial light is best used as a supplement to your winter source if you bring your plants indoors during the winter months.

These strategies apply to summer growing (winter dormant) succulents. As you will discover, many genera are winter growing (summer dormant) which definitely makes providing sufficient light even more challenging. However it is possible!

How can you tell if your plants are receiving proper light? Their general appearance will be compact with the distance between the leaves very short. Leaves will also be small not big and floppy. Rosettes of leafy succulents such as Echeveria will be tight while leaves and bodies of extremely succulent types such as lithops will be compact and colorful, not bloated and soft looking.

This is a good illustration of what can happen to valuable plants if not given correct light levels.

These two Pachypodium horombense are the same age. The specimen on the right has been given proper light while the one on the left is etiolated and ruined from low light. There is no way to reverse the etiolation.

internode.jpg (11476 bytes)

Some of the most light sensitive succulents are the Crassulaceae (echeveria, crassula, graptopetalum, kalanchoe, sedum, etc.), Mesembs (lithops, conophytum, etc.) and Apocynaceae (pachypodium, adenium) while some of the least light sensitive are the Liliaceae (aloes, haworthias), many euphorbias, sansevierias, and stapeliads.

There are many factors to consider if you want to grow first rate, truly beautiful plants but by far, providing sufficient light is the most important. There is hardly anything more unattractive or that reflects poor cultivation technique than an etiolated or stretched out succulent. Etiolation is not reversible, unless the subject can be started again from a cutting, so once this occurs, the plant is ruined. Study your conditions and adopt a strategy for providing proper light. There is no substitute.

Temperature

Most collectable succulents, which includes all the plants you will find on this web site, are not hardy. Although a few Agaves and Sedums might take a few degrees of frost, they will not tolerate freezing temperatures.

We maintain a minimum of 55 F year round for most plants while keeping our most sensitive species at 60 F.

Maximum temperatures are usually determined by weather conditions and succulents are well adapted to tolerate temperatures slightly over 100 F. Prolonged exposure to excessive heat usually prompts most plants to simply go dormant and wait it out.

Many plants can however be damaged by excessive heat and if you are growing in a greenhouse or any other type of solar structure, constant air movement is essential. Hot stagnant air will rapidly damage most succulents.

Watering

When and how much to water your plants has always been a controversial subject. Far too much complexity has been made of this very basic element of cultivation that we all must practice.
Most importantly, it’s crucial to your development of a sound cultural technique that you realize many elements cannot be prescribed or decided for you. You must observe. Watering is certainly one of these elements and you alone must decide.

The general idea should be not how much but when to water, and this is largely determined by your environment. If your conditions are good and you are using a quality growing medium, most plants will dry out in just a few days. So as a good starting point use this simple rule: do not let containers become dust dry at any time. It works. Water, wait until the plant uses what you gave it, then water again.

How can you tell if a plant has used what you gave it? Pick it up. If the pot feels light, water until it appears at the drainage holes. With a little experience, you will quickly be able to tell if water is needed just by looking.

Don’t think of watering as an exact science where every drop must be measured. It’s just not that critical. Make sure your plants are well watered and forget it. Yes there are some succulents that are more sensitive to over and under watering but observation and experience will ready you for these.

When watering, use a good breaker on your hose or a soft rose on your can. This prevents root damage caused from washed out mix. And finally do not push anything into your containers to test the moisture level. This means your finger or those awful dreaded moisture meter probes. Succulents have delicate fragile roots and you will only damage them. Broken roots can rapidly lead to rotted plants from this bad novice habit.

Dormancy

The least understood and most critical time for cultivating succulents is the dormancy or rest period. Most losses occur during or shortly after this time because plants are kept too dry and not monitored. This is the number one reason for failure.

Dormancy is a fact of life. Plants gradually move into a rest period in response to dropping light and temperature levels. They need this break to stay healthy. Your job is to coast them through it.

The first sign that a plant is entering dormancy is that it stops growing. Soon after, leaves begin to yellow and drop, rosettes tighten and contract, or for very succulent groups such as mesembs, bodies can pull themselves into the soil and develop a papery covering as protection.

In October, the Pachypodium densiflorum (winter dormant) on the left shows the first signs of oncoming dormancy by shedding leaves from the bottom up.

The Haworthia cooperi on the right (summer dormant) has likewise begun its resting period but in June. Notice how the individual rosettes have contracted and closed.

dormant pachy.jpg (14819 bytes) dormant haworthia.jpg (13947 bytes)

You may not see much happening on the outside, but even in this state, your plants are not just sitting there. Transpiration is still going on and this moisture must be replaced. They need feeder roots to take up this moisture so naturally plants cannot be kept so dry that these roots desiccate and die. This can easily happen to slow growing species and the consequences will not become apparent until spring when growth commences and plants begin to fail. Plants are failing in April and May because of what you did over the winter months. Signs of trouble often take months to appear.

So how often should you water during the rest period? Again it largely depends on your conditions, i.e. how fast they dry out. If you live where it’s cool during the winter, your plants will rapidly dry from heating equipment being present so one or two waterings per week may be required. If you live in a mild climate, possibly every other week will work. Just water, give them a good dry spell to the point where pots feel light but not dust dry, then water again.

What about the plants that are summer dormant and how should they be treated? Since this group is resting during the warmest time of the year, they will dry out much faster than the winter dormant species and therefore require more frequent waterings. As a starting point, water these every other time you water your summer growers but again, it completely depends on your conditions. During extremely hot weather, they may need water every day.

It’s important to remember that you can’t force your plants into or out of dormancy by withholding or applying moisture. The one exception to this is the mistaken advice one often hears that succulents should be kept completely dry when dormant. In this case they will indeed go dormant but unfortunately it will likely be permanent.

To better understand dormancy and its role in your cultivation, you must be aware of when your plants are actually dormant. Succulents can be organized by genus into the two groups of winter and summer dormant with the most popular genera presented in our Dormancy Table. There are a few exceptions for individual species.

DORMANCY TABLE

WINTER DORMANT

This group is generally regarded as the “summer growers”. They have adapted to our northern hemisphere cycle and are dormant from November through February. Many of these will also enter a pseudo rest period for a few weeks during the hottest part of the summer before putting on a final burst of growth in September and October.

SUMMER DORMANT

Usually referred to as the “winter growers”, these genera are dormant during the warmer months of May through August. Their primary growth actually occurs during autumn and spring while slowing considerably during true winter. Many will exhibit marginal growth during the summer months as well especially in the Lily and Crassulaceae families.

Adenia
Adenium
Agave
Alluaudia
Brachystelma
Bursera
Calibanus
Ceropegia
Cissus
Cyphostemma
Didieria
Dorstenia
Echeveria
Encephalartos
Euphorbia
Ficus
Fockea
Huernia
Ibervillea
Ipomoea
Jathropha
Lithops
Monadenium
Moringa
Operculicarya
Pachypodium
Pedilanthus
Plumeria
Pseudolithos
Pterodiscus
Raphionacme
Siningia
Stapelianthus
Synadenium
Tillandsia
Trichocaulon
Trichodiadema
Xerosicyos
Adromischus
Aeonium
Aloe
Anacampseros
Astroloba
Avonia
Bowiea
Bulbine
Ceraria
Conophytum
Cotyledon
Crassula
Dioscorea
Dudleya
Fouqueria
Gasteria
Gibbaeum
Graptopetalum
Graptoveria
Haemanthus
Haworthia
Kalanchoe
Neohenricia
Othonna
Pachycormus
Pachyphytum
Pachyveria
Pelargonium
Peperomia
Portulacaria
Sansevieria
Sarcocaulon
Sedeveria
Sedum
Senecio
Stomatium
Talinum
Tylecodon

Making Changes - Timing

When to repot, prune excess growth, take cuttings, or in any way physically disturb your plants is closely related to dormancy. Succulents differ from many other types of plants when it comes to making changes and the last thing you want to do is disturb them when they are resting. Rare slow growing species are particularly sensitive and drastic changes can indeed be fatal.

When repotting, wait until you see signs of new growth. Shaping or trimming back excess growth is best done right before the growth period. For summer growers this would be March and for winter growers, it means August. Fast growing robust species can usually be repotted or pruned anytime.

Growing In Containers

Cultivating succulents in containers is vastly different than other plant groups. Using the right size pot has a huge effect on the appearance of any plant. It’s a natural tendency to want to give your plants plenty of root space in the mistaken belief that this will make them grow better or faster. In fact it has the opposite effect as most succulents will slow to a crawl. Many slow growing rare species stop altogether because they just don’t like sitting in a large volume of moist mix. Most experienced growers eventually rethink how they pot and abandon the urge to overpot.

When repotting, go up only inch in pot size. For larger plants in 5 inch or larger containers, you can safely increase in one inch increments. If you use a container that is too large, the roots will grow out of proportion to the rest of the plant and most of the growth energy will be channeled to the branches and leaves. One look at a plant with a large crown of thin branches and floppy leaves usually reveals a container that is too large.

The right size container makes a big difference when repotting.

The Cissus tuberosa on the left has been kept in the same 3 inch pot for 4 years and has developed a nice caudex. The plant on the right was started at the same time from the same size cutting but over potted in a 4 inch container.

cissus tuberosa.jpg (7304 bytes)

When repotting, disturb the roots as little as possible. Usually the root ball will come out intact in one solid piece. Leave it this way and do not attempt to crush or spread it out like you would for a tropical. This will only set the plant back and can quickly lead to fatal root rot. Also do not put old pot chards, gravel, or anything else in the bottom of your container. This will actually promote root tip decay. Simply use a piece of screen wire to cover the drainage hole.

Supplies: mix, nutrients, and containers

MIX - mix is a term used in the horticulture trade for growing medium and is always a controversial subject. Exotic formulae and wildly conflicting advice abound and it’s difficult for the newcomer to sort it out. Using a quality mix is absolutely vital to growing superb plants and you shouldn’t think of it as just “dirt” you put in the container along with your plant.

Is it better to buy commercial mix or make your own? The answer is clearly in favor of commercial products. Note that we are referring to professional products and not consumer type mixes like the generic “cactus soil” you might find at the discount store. The manufacturing of growing medium is complex and technical and is best left to specialized industry. If you choose to make your own, keep in mind that there are many issues to consider for which most of us are not prepared.

There have been great advances in the last 15 years in commercial growing medium and the trend is definitely toward soilless mixes. These come in a variety of formulations with the composted bark being the best. Few growers today use soil based medium as the results realized with soilless mixes are so outstanding.

Simply stated, soilless mixes are based on the matrix concept which is nothing more than a given volume of semi-uniform size particles which provides for maximum growth. Nutrients are then added as fertilizer in solution or incorporated dry into the matrix. The matrix is a carefully constructed blend of composted bark (not landscaping bark), horticultural grade peat (not more than 20%), perlite (baked pumice), vermiculite, and a buffering agent to adjust and stabilize pH. It contains no field soil or aggregate whatsoever.

Two important physical characteristics to consider for any good mix are drainage and weight. One common myth surrounding the notion of what constitutes a proper mix for succulents is the idea that all moisture must absolutely drain away very rapidly leaving no excess, and consequently no reserve, so as to avoid failure from rot. You may indeed avoid root rot with a super fast draining mix but you will also avoid normal growth as your plants will slow to a glacial pace. A good mix must make both moisture and nutrients available and one that drains too rapidly lacks this essential function.

The very worst mix is a heavy mix and should be avoided at all cost. For roots to develop and function properly they need oxygen for respiration. A quality mix will allow oxygen to enter and carbon dioxide and other gasses to escape and therefore must be light in weight. Good respiration is essential for a large vigorous root system and general plant health.

A heavy mix will simply suffocate roots and is usually one which contains aggregate of some sort which should be avoided. Common aggregate used includes sand, gravel, turface, and pumice. Agricultural pumice is used to some degree in the southwestern U.S. as a growing matrix because it is readily available. It is very warm in this region and plants grown in this media will dry out at a sufficient rate but in a more temperate climate, such as the northern and eastern U.S., pumice is much too heavy and soggy. This is because it has an open-celled structure. Superior results are obtained with perlite, which is closed-celled, over pumice.

A major problem for the hobbyist grower is finding a source for soilless mix. A small number of well stocked garden centers do have them for sale but a good alternative is to inquire at a local commercial greenhouse business. The owners are usually dedicated plant lovers and will be more than willing to supply you with a bag or two.

These mixes are formulated for greenhouse crops grown in containers and when used for succulents need to be slightly adjusted with perlite. A good starting point is three parts mix to one part perlite. You will not be changing the basic design of the mix but do not overdo the perlite. Never add other ingredients such as soil or aggregate which will defeat the entire soilless concept.

A constructive way to think about your growing medium is that it should provide some margin of error in watering. One often hears such mistaken advice to the effect that what works for one could be disastrous for another. A quality mix will perform well in a variety of conditions. If you experience frequent plant losses, you may want to consider another mix no matter how good you think your current one is. Go slowly when making changes. Experiment with just a few plants you are familiar with and observe results.

NUTRIENTS - it’s essential to provide nutrients in some form during the growing season and then taper off to none when your plants are dormant. A constant low dosage balanced water soluble fertilizer every time you water (constant feed) is preferred.

Use a good commercial brand such as Peters and avoid hobby or gimmick type products. Quality fertilizers can be found at most garden centers and come in many formulations. A general purpose 20-20-20 or 20-10-20 works well with succulents. There are also formulae with added trace elements for use with soilless mixes and these are very beneficial. If you opt for the low dosage constant feed schedule, mix at recommended strength which will yield about 50ppm nitrogen. Adjust to higher rates if you feed less often (pulse feed).

An alternative to water soluble formulations is resin coated time release fertilizer. This is incorporated into your mix or applied as a top dressing and lasts for a specified time. Excellent brands are Nutricote and Osmocote in 13-13-13, 180 day formula.

Not all succulents need feeding. Many groups become soft and unhealthy if added nutrients are applied and look best if grown lean. These include most of the Crassulaceae (echeveria, crassula, sedum, graptopetalum, etc.), almost all mesembs (lithops, etc.), and senecios.

CONTAINERS - it’s important to use the correct size container as explained above but should you use plastic or terra cotta? Many consider this an aesthetic decision but there’s more to it.

Plants simply grow better in plastic containers because more moisture is available. If you are growing in terra cotta (clay) pots, you will have to water 3-4 times more often because they dry at an alarming rate. This is especially true for small sizes.

Most growers use plastic for 6 inches and smaller and terra cotta for over 6 inches and this works well. Also you will get a more developed better root system with round pots rather than the square design. Most importantly, all containers must have a bottom drainage hole.

Pests

Fortunately succulent collections are not attractive to most pests. Fungal and viral attacks are seldom seen so it’s usually just insects that must be kept in check. Plants and insects are natural companions. If you have plants then you’ll have insects. If you discover an outbreak of some insect pest, there is seldom reason for panic. Your job is simply to keep insects under control. You will never eliminate them completely.

By far the most common and persistent insect succulent growers must face is the ubiquitous mealybug. There are several species of it but it’s the citrus or greenhouse mealybug that is attracted to succulents. Adults are about one eighth inch in size and have a white mealy epidermis. They bear live young (crawlers) in white cottony masses on the underside of leaves and in cracks and crevices especially on soft new growth. They exude a sticky sugary substance which is greatly attractive to other insects such as most ants which will then transport the crawlers to other plants. Keep ants in check and you automatically control many other insects.

Succulent enemy number one is the common mealybug.

An infestation can quickly get out of control such as the one building on this Cyphostemma hardyi. Look for them on the underside of leaves, on new growth, and on flowers. You will often have hundreds of tiny crawlers that are less than one millimeter in size that cannot be seen with the unassisted eye.

mealy group.jpg (12301 bytes) mealy closeup.jpg (12079 bytes)

Mealybug is easy to control and is seldom fatal unless left unattended. Mites, scale, and white fly are occasionally attracted to succulents, pose a more serious problem, and are difficult to eradicate. Mites, which are not true insects, are voracious sucking pests and are attracted to hot dry conditions. A poorly ventilated greenhouse full of underwatered plants is prime territory. Scale and white fly are very persistent and difficult to eliminate unless caught at the right time in their life cycle. Volumes of information exists on these pests and a little research on your part will go a long way in identifying and controlling them. The internet and your county extension office are excellent sources for help.

EASY EFFECTIVE CONTROLS - rubbing alcohol on a Qtip will render the odd mealybug or two harmless but what about several badly infested plants with hundreds of tiny crawlers embedded in the delicate growing apex? Try blasts of tap water applied with a Fogg-It nozzle on a trigger type hose shut-off. A few minutes of pulsating blasts of ordinary tap water worked in very close in all the difficult to reach places will render just about any plant squeaky clean. It will even clean off badly encrusted scale which is a very difficult job.

A FOGG-IT nozzle is a great tool for cleaning plants. It means business and works wonders for insects, weed seeds, and even spent leaves.

Combine it with a trigger type shut-off and you have a deadly weapon to use on insects.

foggit.jpg (11000 bytes) foggit_trigger.jpg (6393 bytes)

Fogg-It nozzles are inexpensive and available from hobby greenhouse suppliers and good garden centers. Use the blue 4 gpm heavy volume size. You could even improvise with the kitchen sink sprayer but outside with the garden hose is usually more practical. This may sound a bit too simple but try it and see how effective it is.

CHEMICAL CONTROLS - if things are out of hand and you are dealing with many badly infested plants, chemical controls are sometimes necessary. The number one rule is absolutely do not, repeat do not, use petroleum based products on succulents. These are usually labeled “liquid” this or that and are designated “EC” or just “E”. The petroleum base in EC’s will severely burn succulents so avoid them at all costs. Systemic pesticides have become popular but the concept of making the entire plant toxic creates personal exposure problems beyond what many growers consider safe.

Most wettable powders and water based or aqueous suspension insecticides can be used on succulents with no phytotoxicity. But again what product to use for what insect requires a little homework on your part. A recommendation from the garden center or a friend won’t do. Always go slowly when trying something new. Never apply an untested chemical to your entire collection. Do a controlled application to just a few test plants instead.

Finally if you are an active collector who frequently acquires plant material from many sources, then it’s inevitable that you will bring in new insects. A good hand lens or loupe of 6x-10x therefore becomes a necessity for inspecting new arrivals and your collection up close and personal.

Basic Equipment List

WATERING - A good watering device with a soft breaker is essential. A simple hose or watering can with a rose type breaker is fine. We prefer a bonsai watering nozzle on a hose with some sort of shut-off to regulate flow. A bonsai nozzle is a super soft breaker fitted to a short wand and is available from most sources that sell bonsai tools.

TWEEZERS - A pair of thin 7"- 9" tweezers is invaluable. Again bonsai type tweezers are best.

MAGNIFICATION - A closeup lens of anywhere from 4x-10x is basic. From a simple magnifying glass to an optically superior photo loupe, magnification is essential for controlling pests and studying your plants.

LABELS - It's important to label each plant with genus, species, acquisition date, and source. When you lose one of your favorites, you at least have a chance of replacing it with this information. Lead pencil on vinyl labels is as permanent as we have found. Solar exposure quickly renders other materials to compost.

POTTING - A good potting tray and trowel are most helpful. A large restaurant busing tray is great and is readily available from any restaurant supply. We like one that holds about a cubic foot of mix.

POTS - Keep a good supply of pots on hand. Whether you prefer plastic or terracotta, a nice selection in half inch increments is always in demand.