4 March 2022

Cactus care

Cacti are definitely unique and it's no secret that this family of plants is a hit with collectors and plant lovers around the world with their varied shapes and amazing colours. These plants are ideal for people who tend to forget about watering as they have adapted to the extreme conditions of deserts. Cacti store reserves of juices or liquids in their tissues in order to cope with drier periods. Although cacti are simple to care for, there are a few important points to keep in mind in order to provide a favourable environment for their development.

History & origins
Natural environment
Plant Care & Advice
Watering
Potting soil
Potting
Pruning the pot
Flowering
Hardiness
Lighting
Comestibility
Toxicity
Species

History & origins

There are several references to cacti dating back as far as the 14th century. Cacti appear on the drawings and sculptures of ancient civilizations around the world, such as the Aztecs in Mexico and the Moches in Peru.

The nomenclature of the Cactaceae has fluctuated greatly throughout history. Indeed, the various species that we know today did not exist in Europe during antiquity and arrived in progressive waves after the "discovery" of America.

The interest in cacti during the 20th century led to excessive collecting and poaching, which caused some species to disappear completely from the wild. Fortunately, new species or varieties continue to be found and discovered every year!

Natural environment

With over 2,000 species in almost 139 different genera, cacti are native to North and South America, from British Columbia and Alberta to Chile and Argentina.

Mexico has the largest number and variety of cactus species in the world. The only cacti native to the Old World are members of the genus Rhipsalis, found in East Africa, Madagascar and Sri Lanka, among other places.

Although some cactus species live in humid tropical or subtropical areas, most live in desert regions and have adapted to these regions with unique characteristics that allow them to conserve water and survive the intense sun of these regions.

How to care for your cactus: care & advice

Who hasn't heard someone say that cacti don't need water and are excellent plants for beginners? You may be surprised to learn that this is partly untrue and that one of the most important factors for a healthy collection is adequate watering. While it is true that cacti do not require much water and can easily tolerate an oversight or two, it is still important to be aware of the needs of different types of cacti in order to provide them with a favourable growing environment.

How often should cacti be watered?

During the growing season, generally from April to the end of September, we recommend that you only water your cacti when the potting soil is dry, about once a week. This can vary depending on the environment and the species of cactus, so the most important thing is to make sure you let the potting soil dry out 100% before watering again!

During the winter, as the light decreases and the temperature drops, cacti often go into a dormant period. If your plant is kept in a cool room between 7 and 14 degrees, it is recommended that you never (or hardly ever) water it during this period, which is usually from October to March.

Watering tropical vs. desert cacti

There are many different types of cactus that come from different places around the world. There are several species that come from tropical environments as well as other species that come from desert environments. Where they come from is a factor that has a real impact on the watering requirements of individual plants. Generally speaking, desert cacti require less frequent watering than tropical cacti, which require more regular watering. It is therefore important to know the needs of the cacti in your collection in order to provide them with adequate watering.

Different watering methods for cacti

Basin method

This method consists of soaking plants in a pot (with holes) in a basin of water. It is important to ensure that the plant is not in direct contact with the water. Remove the pot from the basin as soon as the soil on the surface becomes wet and let the plant drain. Be sure not to leave the plant in the water for too long to avoid the risk of root rot.

Benefits

Complete rehydration of the soil;
Creation of canals for the passage of water;
Allows the plant to drink what it really needs;
Better development of the root system;
Avoids rotting in the centre of the plant that could be caused by water accumulation (e.g. when watering a cactus that grows in clusters like a sulcorebutia).

Disadvantages

Does not remove excess mineral salt from the soil;
Takes longer to water;
Requires more handling.

Top watering method

Watering from the top is a more familiar method but still requires special attention. When watering your plant, be sure to wait for the water to drain from the bottom of your hole pot. If your pot does not have a hole in it, you may want to consider transplanting your plants to pots with holes in them to prevent problems.

Caution: It is important not to put water directly on the cactus as this can stain or rot the plant if the air circulation is not adequate.

Benefits

Faster watering;
Allows excess salt to be removed;
Provides better fertilisation.

Disadvantages

Watering the plant may increase the risk of rotting if the water remains in contact with the cactus for too long;
Does not allow for proper watering of the entire root system;
Requires good ventilation.

Choosing the best potting soil for growing cacti

Depending on the type and species of cactus, potting soil requirements may vary. In general, a regular cactus mix can be just as effective as a home-made mix. If you want to provide a suitable environment for a specific type of cactus, we recommend mixing your own potting soil to customise it to your needs.

Potting soil for desert cacti

A good desert cactus potting soil starts with a base of 30% high porosity soil. Then add about 50% pumice and 20% perlite to improve drainage. It is also possible to start with 40% potting soil and 60% pumice and perlite depending on your preference.

Potting soil for epiphytic cacti

The epiphytic cactus potting soil also starts with a base of 30% high porosity potting soil. This is followed by approximately 50% pumice and 20% bark to create a potting soil with excellent drainage and more organic matter.

Potting: how to transplant a cactus?

Most cacti are sold in inadequate potting soil. When repotting, it is best to choose a clay pot that is the same size or wider than it is tall (see the next section on how to choose the right pot).

Here are the steps for successful potting:

Make sure that the chosen pot has a drainage hole;
Moisten your potting soil slightly before use to avoid airborne particles;
Put some potting soil in the bottom of your pot. It is not necessary to add a drainage layer except for large cacti or to add weight to your pot;
Remove the cactus with a folded newspaper or a pair of triple-layered gloves to avoid pricking yourself and to be able to position it properly in the middle of the pot. You can also wrap the cactus in cloth, leaving some excess to create a handle;
Fill the remaining space around the root ball with potting soil and compact lightly;
Wait about 7 days before watering your cactus with room temperature water. This allows the roots to heal and prevents rotting.

Choosing the right pot size

The size of the pot is an important factor to consider when buying your plant as it influences its growth. Ideally, you should buy the pot for repotting at the same time as the plant to avoid buying the wrong size pot. The size of the pot will depend on the size of the plant and should be based on the following two elements

The diameter of the pot

Cacti and a large majority of succulents do not need a large space in width to grow and be healthy. This criterion is therefore not a priority. However, make sure that you leave an inch of space around the base of the cactus so that it can grow well.

The depth of the pot

Always ask about the depth of the roots before choosing a cactus pot. A few extra centimetres of soil should be placed under the roots to allow the plant to air out. If the only pot available is too deep, gravel can be added to the bottom of the pot to reduce the amount of potting soil and increase the speed at which the soil can dry out.

The drainage hole: a super important detail

Ideally, you should always use a pot with an irrigation hole. If you still want to plant in a ceramic planter without a hole (more beautiful, but more risky for the health of your plants), you can drill one with a special drill bit. Make sure you always have water running through the hole to avoid breaking your pot cover by friction. You can also make an even more draining mixture to ensure that excess water drains away more quickly, but you will need to water more often.

Flowering and fertilization of cacti

Cacti are generally known for their spines and varied shapes, but did you know that most cacti also produce amazing flowers in a wide variety of colours? Most cacti bloom after a period of dormancy, which is necessary for these plants to flourish.

To start flowering and allow your cactus to bloom, it is therefore necessary to create a "thermal shock" in order to recreate its natural environment. In nature, this thermal shock often occurs around April and signals the beginning of summer. It is often accompanied by an abundance of light and tells the plant that it is time to reproduce. At this time of the year there is also an acceleration in the growth of cacti, which means that it is important to apply fertiliser more frequently.

There are several species of cactus that flower during the day and at night. Make sure you are familiar with the types of cactus in your collection so that you can provide them with a suitable environment.

Hardiness: is it possible to keep cacti outdoors all year round?

In general, cacti are extremely heat resistant as they originate from desert regions around the world. However, in these areas, temperatures can also drop very low at night, and particularly in winter when it can even snow. Some species, depending on their origin and with the right protection, can therefore naturally withstand very cold, sometimes freezing temperatures.

When cacti are dormant, their metabolism goes down to enable them to survive the colder periods, while waiting for their growing season. For this reason, most species hardly need to be watered during this season.

List of cactus species tolerant between -20C and -35C (Zone 5a / 5b)

Coryphantha vivipara (or Escobaria vivipara) (-20 °C)
Escobaria missouriensis (-20° C)
Escobaria sneedii (-20 °C)
Escobaria robbinsiorum (-20 °C)
Echinocereus reichenbachii var. baleyi (-23 °C)
Echinocereus triglochidiatus (-25 °C)
Echinocereus viridiflorus (-25 °C)
Echinopsis chamaecereus (also called Chamaecereus silvestrii or Lobivia silvestrii) (-20 °C)
Opuntia cymochila (-25 °C)
Opuntia fragilis (-25 °C)
Opuntia humifusa (-25 to -35 °C)
Opuntia polyacantha (-35 °C)
Pediocactus peeblesianus var. fickeisenii (-25 °C)

*Source: https: //www.cactus-encyclo.com/cactus-gel-froid/

Providing the right type of lighting for your cacti

In order to allow the plant to change the chemicals in the soil into assimilable nutrients, it is important to provide adequate light to your cacti during their growing season (usually March to October). If a cactus does not receive adequate light, it will start to grow in an etiolated manner. Its life expectancy will be shortened and it will eventually die of starvation.

There are several factors that can cause the light available to your cacti to not be intense enough to give them optimal development. Remember that depending on the type of window and the orientation of your house, there is much less light coming through than you might think. This is often the case in new buildings that use triple-layered windows with gas and UV protection film. In these cases, we always recommend adding an artificial light.

Some cactus species require less lighting than others. It is therefore important to know the types of cactus in your collection so that you can adapt the lighting to their needs.

Full sun (direct light)

Most desert cacti can handle long periods of full sun without difficulty. Place them on a sunny windowsill facing south, in a greenhouse or under artificial LED light. It is important to always acclimatise the plants properly if you are going to take them outside during the summer to avoid burns that may occur.

Half-shade (subdued or indirect light)

There are also several species that grow in the shelter of bushes and small shrubs in arid areas. These plants generally enjoy light shade and require shelter from the midday sun. Among these species are several epiphytic cacti.

Example: Epiphyllum

Shadow

Some species are shade tolerant, but only for a short time. On the other hand, we often notice that these plants eventually start to grow in pride (wilting).

Adapting to the dormant period

Contrary to what you might think, cacti need a dormant period. We recommend overwintering your cacti in a roomwith low light levels, a constant temperature of 5-10 degrees and low humidity. It is desirable to have a minimum of light during this period because even though the plants do not eat or drink during their resting period, they continue to carry out the photosynthesis that is essential for their survival. This process will make your cacti stronger and more vigorous, give you beautiful blooms in due course and also make them last longer.

Caution: Always research the cycle of each cactus as their dormancy period and light requirements may differ from one species to another.

Edibility and fruits of cacti

There are several species of cactus that are not only edible, but are also known for their unique and exotic tasting fruits.

Pitaya (Dragon Fruit)

The Dragon Fruit, also known by the Spanish name pitaya or pitahaya, is the fruit of the Selenicereus undatus. This exotic fruit has a tropical flavour reminiscent of watermelon. In addition, its high fibre content makes it a suitable dietary food and offers you a large number of vitamins and benefits.

The Peruvian Apple Cactus (Peruvian apple)

Cereus peruvianus, also known as the Peruvian apple cactus, is known for its tall, columnar appearance and low maintenance. The fruit is sweet and slightly acidic, reminiscent of the taste of apricots. It also has a nice crunchy texture and excellent nutritional value.

The Organ Pipe Cactus

Stenocereus thurberi, commonly known as the organ cactus, is a species native to Mexico and the United States. The fruits of this plant have a sweet taste with a succulent texture.

The prickly pear cactus (Cactus de Figue de Barbarie)

Prickly pears are the fruit of the Opuntia ficus-indica, a cactus native to Mexico. When raw and green, prickly pears have a tropical taste. Once they ripen and turn reddish-orange, they have a mild, sweet taste.

The saguaro cactus

The Saguaro fruit comes from the Carnegiea gigantea and has a sweet, subtle taste, not as strong as that of prickly pears. Native to Mexico, this cactus is the only species in the monotypic genus Carnegiea.

Which cacti are poisonous?

Although some cactus plants are edible, there are several species of cactus that are poisonous and not fit for consumption.

Here are 3 types of cacti that are not edible:

The peyote cactus (pronounced 'peyote') contains several alkaloids, including mescaline;
The San Pedro cactus contains a large number of alkaloids, including mescaline;
The Bolivian torch cactus is toxic and contains several alkaloids that can cause a psychedelic effect.

Our favourite cactus species

Cereus forbesii "Spiralis

The Cereus forbesii 'Spiralis', is a candle cactus that has been named after its unique and peculiar shape, causing it to turn on itself as it grows so that it forms a 'spiral'. When in flower, this large cactus develops large showy flowers, making it a welcome addition to any plant collection.

Cereus Forbesii "Spiralis"